Lsi 53C875A Users Manual LSI53C875A PCI To Ultra SCSI Controller Technical

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TECHNICAL
MANUAL

LSI53C875A
PCI to Ultra SCSI
Controller
Version 2.0
December 2000

S14047

This document contains proprietary information of LSI Logic Corporation. The
information contained herein is not to be used by or disclosed to third parties
without the express written permission of an officer of LSI Logic Corporation.
LSI Logic products are not intended for use in life-support appliances, devices,
or systems. Use of any LSI Logic product in such applications without written
consent of the appropriate LSI Logic officer is prohibited.
Document DB14-000143-01, Second Edition (December 2000).
This document describes the LSI Logic LSI53C875A PCI to Ultra SCSI Controller
and will remain the official reference source for all revisions/releases of this
product until rescinded by an update.
To receive product literature, visit us at http://www.lsilogic.com.
LSI Logic Corporation reserves the right to make changes to any products herein
at any time without notice. LSI Logic does not assume any responsibility or
liability arising out of the application or use of any product described herein,
except as expressly agreed to in writing by LSI Logic; nor does the purchase or
use of a product from LSI Logic convey a license under any patent rights,
copyrights, trademark rights, or any other of the intellectual property rights of
LSI Logic or third parties.
Ultra SCSI is the term used by the SCSI Trade Association (STA) to describe
Fast-20 SCSI, as documented in the SCSI-3 Fast-20 Parallel Interface standard,
X3,277-199X.
Copyright © 2000 by LSI Logic Corporation. All rights reserved.
TRADEMARK ACKNOWLEDGMENT
The LSI Logic logo design, TolerANT, and SCRIPTS are registered trademarks
or trademarks of LSI Logic Corporation. All other brand and product names may
be trademarks of their respective companies.
HH

Preface

This book is the primary reference and technical manual for the
LSI53C875A PCI to Ultra SCSI Controller. It contains a complete
functional description for the product and also includes complete physical
and electrical specifications.

Audience
This manual provides reference information on the LSI53C875A PCI to
Ultra SCSI Controller. It is intended for system designers and
programmers who are using this device to design an Ultra SCSI port for
PCI-based personal computers, workstations, servers or embedded
applications.

Organization
This document has the following chapters and appendixes:

•

Chapter 1, General Description includes general information about
the LSI53C875A.

•

Chapter 2, Functional Description describes the main functional
areas of the chip in more detail, including interfaces to the SCSI bus
and external memory.

•

Chapter 3, Signal Descriptions contains pin diagrams and signal
descriptions.

•

Chapter 4, Registers describes each bit in the operating registers,
and is organized by register address.

•

Chapter 5, SCSI SCRIPTS Instruction Set defines all of the SCSI
SCRIPTS instructions that are supported by the LSI53C875A.

Preface

iii

•

Chapter 6, Electrical Specifications contains the electrical
characteristics and AC timing diagrams.

•

Appendix A, Register Summary is a register summary.

•

Appendix B, External Memory Interface Diagram Examples contains
several example interface drawings for connecting the LSI53C875A
to external ROMs.

Related Publications
For background information, please contact:
ANSI
11 West 42nd Street
New York, NY 10036
(212) 642-4900
Ask for document number X3.131-199X (SCSI-2)
Global Engineering Documents
15 Inverness Way East
Englewood, CO 80112
(800) 854-7179 or (303) 397-7956 (outside U.S.) FAX (303) 397-2740
Ask for document number X3.131-1994 (SCSI-2); X3.253 (SCSI-3
Parallel Interface)
ENDL Publications
14426 Black Walnut Court
Saratoga, CA 95070
(408) 867-6642
Document names: SCSI Bench Reference, SCSI Encyclopedia,
SCSI Tutor
Prentice Hall
113 Sylvan Avenue
Englewood Cliffs, NJ 07632
(800) 947-7700
Ask for document number ISBN 0-13-796855-8, SCSI: Understanding
the Small Computer System Interface
LSI Logic World Wide Web Home Page
www.lsilogic.com

Preface

PCI Special Interest Group
2575 N.E. Katherine
Hillsboro, OR 97214
(800) 433-5177; (503) 693-6232 (International); FAX (503) 693-8344

Conventions Used in This Manual
The word assert means to drive a signal true or active. The word
deassert means to drive a signal false or inactive.
Hexadecimal numbers are indicated by the prefix “0x” —for example,
0x32CF. Binary numbers are indicated by the prefix “0b” —for example,
0b0011.0010.1100.1111.

Revision Record

Revision

Date

Remarks

Preliminary

5/00

Preliminary draft version of the manual.

1.0

6/00

Preliminary version of the manual.

2.0

12/00

Final version of the manual.

Preface

Contents

Chapter 1

Chapter 2

General Description
1.1
New Features in the LSI53C875A
1.2
Benefits of Ultra SCSI
1.3
TolerANT® Technology
1.4
LSI53C875A Benefits Summary
1.4.1
SCSI Performance
1.4.2
PCI Performance
1.4.3
Integration
1.4.4
Ease of Use
1.4.5
Flexibility
1.4.6
Reliability
1.4.7
Testability
Functional Description
2.1
PCI Functional Description
2.1.1
PCI Addressing
2.1.2
PCI Bus Commands and Functions Supported
2.1.3
PCI Cache Mode
2.2
SCSI Functional Description
2.2.1
SCRIPTS Processor
2.2.2
Internal SCRIPTS RAM
2.2.3
64-Bit Addressing in SCRIPTS
2.2.4
Hardware Control of SCSI Activity LED
2.2.5
Designing an Ultra SCSI System
2.2.6
Prefetching SCRIPTS Instructions
2.2.7
Opcode Fetch Burst Capability
2.2.8
Load and Store Instructions
2.2.9
JTAG Boundary Scan Testing
2.2.10 SCSI Loopback Mode

Contents

1-3
1-3
1-4
1-4
1-5
1-6
1-6
1-6
1-7
1-8
1-8

2-2
2-2
2-3
2-9
2-16
2-17
2-18
2-19
2-19
2-20
2-21
2-22
2-22
2-23
2-23

vii

2.3
2.4

2.5

Chapter 3

viii

2.2.11 Parity Options
2.2.12 DMA FIFO
2.2.13 SCSI Bus Interface
2.2.14 Select/Reselect During Selection/Reselection
2.2.15 Synchronous Operation
2.2.16 Interrupt Handling
2.2.17 Chained Block Moves
Parallel ROM Interface
Serial EEPROM Interface
2.4.1
Default Download Mode
2.4.2
No Download Mode
Power Management
2.5.1
Power State D0
2.5.2
Power State D1
2.5.3
Power State D2
2.5.4
Power State D3

Signal Descriptions
3.1
LSI53C875A Functional Signal Grouping
3.2
Signal Descriptions
3.2.1
Internal Pull-ups on LSI53C875A Signals
3.3
PCI Bus Interface Signals
3.3.1
System Signals
3.3.2
Address and Data Signals
3.3.3
Interface Control Signals
3.3.4
Arbitration Signals
3.3.5
Error Reporting Signals
3.3.6
Interrupt Signal
3.4
SCSI Bus Interface Signals
3.4.1
SCSI Bus Interface Signal
3.4.2
SCSI Signals
3.4.3
SCSI Control Signals
3.5
GPIO Signals
3.6
ROM Flash and Memory Interface Signals
3.7
Test Interface Signals
3.8
Power and Ground Signals
3.9
MAD Bus Programming

Contents

2-24
2-27
2-32
2-33
2-34
2-37
2-44
2-48
2-50
2-50
2-51
2-51
2-52
2-52
2-53
2-53

3-2
3-3
3-3
3-4
3-4
3-5
3-6
3-7
3-7
3-8
3-8
3-8
3-9
3-9
3-10
3-11
3-12
3-13
3-14

Chapter 4

Chapter 5

Chapter 6

Registers
4.1
PCI Configuration Registers
4.2
SCSI Registers
4.3
64-Bit SCRIPTS Selectors
4.4
Phase Mismatch Jump Registers
SCSI SCRIPTS Instruction Set
5.1
Low Level Register Interface Mode
5.2
High Level SCSI SCRIPTS Mode
5.2.1
Sample Operation
5.3
Block Move Instruction
5.3.1
First Dword
5.3.2
Second Dword
5.4
I/O Instruction
5.4.1
First Dword
5.4.2
Second Dword
5.5
Read/Write Instructions
5.5.1
First Dword
5.5.2
Second Dword
5.5.3
Read-Modify-Write Cycles
5.5.4
Move To/From SFBR Cycles
5.6
Transfer Control Instructions
5.6.1
First Dword
5.6.2
Second Dword
5.7
Memory Move Instructions
5.7.1
First Dword
5.7.2
Read/Write System Memory from SCRIPTS
5.7.3
Second Dword
5.7.4
Third Dword
5.8
Load and Store Instructions
5.8.1
First Dword
5.8.2
Second Dword
Electrical Specifications
6.1
DC Characteristics
6.2
TolerANT Technology Electrical Characteristics

Contents

4-1
4-18
4-99
4-103

5-1
5-2
5-3
5-6
5-6
5-13
5-13
5-14
5-21
5-22
5-22
5-23
5-23
5-24
5-25
5-26
5-32
5-32
5-33
5-34
5-34
5-35
5-35
5-36
5-37

6-1
6-5

6.3
6.4

6.5
6.6

AC Characteristics
PCI and External Memory Interface Timing Diagrams
6.4.1
Target Timing
6.4.2
Initiator Timing
6.4.3
External Memory Timing
SCSI Timing Diagrams
Package Diagrams

Appendix A

Appendix B

External Memory Interface Diagram Examples

6-9
6-11
6-13
6-19
6-35
6-52
6-58

Index
Customer Feedback
Figures
1.1
1.2
2.1
2.2
2.3
2.4
2.5
2.6
2.7
3.1
5.1
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8

Typical LSI53C875A System Application
Typical LSI53C875A Board Application
LSI53C875A Block Diagram
Parity Checking/Generation
DMA FIFO Sections
LSI53C875A Host Interface SCSI Data Paths
Regulated Termination for Ultra SCSI
Determining the Synchronous Transfer Rate
Block Move and Chained Block Move Instructions
LSI53C875A Functional Signal Grouping
SCRIPTS Overview
Rise and Fall Time Test Condition
SCSI Input Filtering
Hysteresis of SCSI Receivers
Input Current as a Function of Input Voltage
Output Current as a Function of Output Voltage
External Clock
Reset Input
Interrupt Output

Contents

1-2
1-2
2-2
2-27
2-28
2-29
2-33
2-35
2-45
3-2
5-5
6-7
6-7
6-7
6-8
6-8
6-9
6-10
6-11

6.9
6.10
6.11
6.12
6.13
6.14
6.15
6.16
6.17
6.18
6.19
6.20
6.21
6.22
6.23
6.24
6.25
6.26
6.27
6.28
6.29
6.30
6.31
6.32
6.33
6.34
6.35
6.36
6.37
6.38
6.39
B.1
B.2

PCI Configuration Register Read
PCI Configuration Register Write
32-Bit Operating Register/SCRIPTS RAM Read
64-Bit Address Operating Register/SCRIPTS RAM Read
32-Bit Operating Register/SCRIPTS RAM Write
64-Bit Address Operating Register/SCRIPTS RAM Write
Nonburst Opcode Fetch, 32-Bit Address and Data
Burst Opcode Fetch, 32-Bit Address and Data
Back-to-Back Read, 32-Bit Address and Data
Back-to-Back Write, 32-Bit Address and Data
Burst Read, 32-Bit Address and Data
Burst Read, 64-Bit Address and Data
Burst Write, 32-Bit Address and Data
Burst Write, 64-Bit Address and 32-Bit Data
External Memory Read
External Memory Write
Normal/Fast Memory (≥ 128 Kbytes) Single Byte
Access Read Cycle
Normal/Fast Memory (≥ 128 Kbytes) Single Byte
Access Write Cycle
Normal/Fast Memory (≥ 128 Kbytes) Multiple Byte
Access Read Cycle
Normal/Fast Memory (≥ 128 Kbytes) Multiple Byte
Access Write Cycle
Slow Memory (≤ 128 Kbytes) Read Cycle
Slow Memory (≤ 128 Kbytes) Write Cycle
≤ 64 Kbytes ROM Read Cycle
≤ 64 Kbyte ROM Write Cycle
Initiator Asynchronous Send
Initiator Asynchronous Receive
Target Asynchronous Send
Target Asynchronous Receive
Initiator and Target Synchronous Transfer
LSI53C875A 160-Pin PQFP Mechanical Drawing
169-Pin BGA Mechanical Drawing
16 Kbyte Interface with 200 ns Memory
64 Kbyte Interface with 150 ns Memory

Contents

6-13
6-14
6-15
6-16
6-17
6-18
6-20
6-22
6-24
6-26
6-28
6-30
6-32
6-34
6-36
6-40
6-42
6-43
6-44
6-46
6-48
6-49
6-50
6-51
6-52
6-53
6-54
6-55
6-57
6-58
6-61
B-1
B-2

B.3
B.4

128 Kbytes, 256 Kbytes, 512 Kbytes, or 1 Mbyte
Interface with 150 ns Memory
512 Kbyte Interface with 150 ns Memory

B-3
B-4

Tables
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
3.11
3.12
3.13
3.14
3.15
4.1
4.2
4.3
4.4
4.5
4.6
5.1

xii

PCI Bus Commands and Encoding Types for the
LSI53C875A
PCI Cache Mode Alignment
Bits Used for Parity Control and Generation
SCSI Parity Control
SCSI Parity Errors and Interrupts
Parallel ROM Support
Mode A Serial EEPROM Data Format
Power States
LSI53C875A Internal Pull-ups
System Signals
Address and Data Signals
Interface Control Signals
Arbitration Signals
Error Reporting Signals
Interrupt Signal
SCSI Bus Interface Signal
SCSI Signals
SCSI Control Signals
GPIO Signals
ROM Flash and Memory Interface Signals
Test Interface Signals
Power and Ground Signals
Decode of MAD Pins
PCI Configuration Register Map
SCSI Register Address Map
Examples of Synchronous Transfer Periods and Rates
for SCSI-1
Example Transfer Periods and Rates for Fast SCSI-2
and Ultra SCSI
Maximum Synchronous Offset
SCSI Synchronous Data FIFO Word Count
SCRIPTS Instructions

Contents

2-4
2-12
2-25
2-26
2-26
2-49
2-51
2-52
3-3
3-4
3-5
3-6
3-7
3-7
3-8
3-8
3-9
3-9
3-10
3-11
3-12
3-13
3-14
4-2
4-19
4-32
4-33
4-34
4-44
5-3

5.2
5.3
5.4
5.5
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
6.10
6.11
6.12
6.13
6.14
6.15
6.16
6.17
6.18
6.19
6.20
6.21
6.22
6.23
6.24
6.25
6.26
6.27
6.28
6.29

SCSI Information Transfer Phase
Read/Write Instructions
Transfer Control Instructions
SCSI Phase Comparisons
Absolute Maximum Stress Ratings
Operating Conditions
Input Capacitance
Bidirectional Signals—MAD[7:0], MAS/[1:0], MCE/, MOE/,
MWE/
Bidirectional Signals—GPIO0_FETCH/, GPIO1_MASTER/,
GPIO[2:4]
Bidirectional Signals—AD[31:0], C_BE[3:0]/, FRAME/,
IRDY/, TRDY/, DEVSEL/, STOP/, PERR/, PAR
Input Signals—CLK, GNT/, IDSEL, RST/, SCLK, TCK,
TDI, TEST_HSC, TEST_RST, TMS, TRST/
Output Signal—TDO
Output Signals—IRQ/, MAC/_TESTOUT, REQ/
Output Signal—SERR/
TolerANT Technology Electrical Characteristics for SE
SCSI Signals
External Clock
Reset Input
Interrupt Output
PCI Configuration Register Read
PCI Configuration Register Write
32-Bit Operating Register/SCRIPTS RAM Read
64-Bit Address Operating Register/SCRIPTS RAM Read
32-Bit Operating Register/SCRIPTS RAM Write
64-Bit Address Operating Register/SCRIPTS RAM Write
Nonburst Opcode Fetch, 32-Bit Address and Data
Burst Opcode Fetch, 32-Bit Address and Data
Back-to-Back Read, 32-Bit Address and Data
Back-to-Back Write, 32-Bit Address and Data
Burst Read, 32-Bit Address and Data
Burst Read, 64-Bit Address and Data
Burst Write, 32-Bit Address and Data
Burst Write, 64-Bit Address and 32-Bit Data
External Memory Read

Contents

5-12
5-24
5-26
5-29
6-2
6-2
6-2
6-3
6-3
6-4
6-4
6-4
6-5
6-5
6-6
6-9
6-10
6-10
6-13
6-14
6-15
6-16
6-17
6-18
6-19
6-21
6-23
6-25
6-27
6-29
6-31
6-33
6-35

xiii

6.30
6.31
6.32
6.33
6.34
6.35
6.36
6.37
6.38
6.39
6.40
6.41
6.42
6.43
6.44
6.45
A.1
A.2

xiv

External Memory Write
Normal/Fast Memory (≥ 128 Kbytes) Single Byte
Access Read Cycle
Normal/Fast Memory (≥ 128 Kbytes) Single Byte
Access Write Cycle
Slow Memory (≤ 128 Kbytes) Read Cycle
Slow Memory (≤ 128 Kbytes) Write Cycle
≤= 64 Kbytes ROM Read Cycle
≤ 64 Kbyte ROM Write Cycle
Initiator Asynchronous Send
Initiator Asynchronous Receive
Target Asynchronous Send
Target Asynchronous Receive
SCSI-1 Transfers (5.0 Mbytes)
SCSI-2 Fast Transfers 10.0 Mbytes (8-Bit Transfers) or
20.0 Mbytes (16-Bit Transfers) 40 MHz Clock
Ultra SCSI Transfers 20.0 Mbytes (8-Bit Transfers) or
40.0 Mbytes (16-Bit Transfers) Quadrupled 40 MHz Clock
160 PQFP Pin List by Location
169 BGA Pin List by Location
LSI53C875A PCI Register Map
LSI53C875A SCSI Register Map

Contents

6-38
6-42
6-43
6-48
6-49
6-50
6-51
6-52
6-53
6-54
6-55
6-55
6-56
6-56
6-60
6-62
A-1
A-2

Chapter 1
General Description

Chapter 1 is divided into the following sections:

•

Section 1.1, “New Features in the LSI53C875A”

•

Section 1.2, “Benefits of Ultra SCSI”

•

Section 1.3, “TolerANT® Technology”

•

Section 1.4, “LSI53C875A Benefits Summary”

The LSI53C875A PCI to Ultra SCSI Controller brings Ultra SCSI
performance to host adapter, workstation, and general computer designs,
making it easy to add a high-performance SCSI bus to any PCI system.
It supports Ultra SCSI transfer rates with Single-Ended (SE) signaling for
SCSI devices.
The LSI53C875A has a local memory bus for local storage of the
device’s BIOS ROM in flash memory or standard EEPROMs. The
LSI53C875A supports programming of local flash memory for updates to
BIOS. Chapter 6, “Electrical Specifications,” has the chip package and
BGA specifications. Appendix B, “External Memory Interface Diagram
Examples,” has system diagrams showing the connections of the
LSI53C875A with an external ROM or flash memory.
The LSI53C875A integrates a high-performance SCSI core, a 64-bit PCI
bus master DMA core, and the LSI Logic SCSI SCRIPTS™ processor to
meet the flexibility requirements of SCSI-3 and Ultra SCSI standards. It
implements multithreaded I/O algorithms with a minimum of processor
intervention, solving the protocol overhead problems of previous
intelligent and nonintelligent adapter designs.
Figure 1.1 illustrates a typical LSI53C875A system and Figure 1.2
illustrates a typical LSI53C875A board application.

LSI53C875A PCI to Ultra SCSI Controller

1-1

Figure 1.1

Typical LSI53C875A System Application

PCI Bus
Interface
Controller

PCI Bus

SCSI Bus

LSI53C875A
PCI to Wide Ultra
SCSI Controller

Fixed Disk, Optical Disk
Printer, Tape, and Other
Peripherals

Processor Bus

PCI Graphic Accelerator

PCI Fast Ethernet

Memory
Controller
Central
Processing
Unit
(CPU)

Figure 1.2

Typical PCI
Computer System
Architecture

Memory

Typical LSI53C875A Board Application

68 Pin
SCSI
Wide
Connector

SCSI Data,
Parity and
Control
Signals

Memory
Address/Data
Bus

Memory Control
Block
Flash EEPROM

LSI53C875A
32 Bit PCI to
SCSI Controller

GPIO[1:0]
Serial EEPROM

PCI Interface
PCI Address, Data, Parity and Control Signals

1-2

General Description

1.1 New Features in the LSI53C875A
The LSI53C875A is a drop-in replacement for the LSI53C875 PCI to
Ultra SCSI Controller, with these additional benefits:

•

Supports 32-bit PCI Interface with 64-bit addressing.

•

Handles SCSI phase mismatches in SCRIPTS without interrupting
the CPU.

•

Supports JTAG boundary scanning.

•

Supports PC99 Power Management.
–

Automatically downloads Subsystem Vendor ID, Subsystem ID,
and PCI power management levels D0, D1, D2, and D3.

•

Improves PCI bus efficiency through improved PCI caching design.

•

Transfers Load/Store data to or from 4 Kbytes of internal SCRIPTS
RAM.

Additional features of the LSI53C875A include:

•

Hardware control of SCSI activity LED.

•

32-bit ISTAT registers (Interrupt Status Zero (ISTAT0), Interrupt
Status One (ISTAT1), Mailbox Zero (MBOX0), Mailbox One
(MBOX1)).

•

Optional 944 byte DMA FIFO supports large block transfers at Ultra
SCSI speeds. The default FIFO size of 112 bytes is also supported.

1.2 Benefits of Ultra SCSI
Ultra SCSI is an extension of the SPI-2 draft standard that allows faster
synchronous SCSI transfer rates. When enabled, Ultra SCSI performs
20 megatransfers per second. The LSI53C875A can perform 16-bit, Ultra
SCSI synchronous transfers as fast as 40 Mbytes/s. This advantage is
most noticeable in heavily loaded systems or with applications with large
block requirements, such as video on-demand and image processing.
An advantage of Ultra SCSI is that it significantly improves SCSI
bandwidth while preserving existing hardware and software investments.
The primary software changes required enable the chip to perform

New Features in the LSI53C875A

1-3

synchronous negotiations for Ultra SCSI rates and to enable the clock
quadrupler. Chapter 2, “Functional Description,” contains more
information on Ultra SCSI design.

1.3 TolerANT® Technology
The LSI53C875A features TolerANT technology, which includes active
negation on the SCSI drivers and input signal filtering on the SCSI
receivers. Active negation actively drives the SCSI Request,
Acknowledge, Data, and Parity signals HIGH rather than allowing them
to be passively pulled up by terminators. Active negation is enabled by
setting bit 7 in the SCSI Test Three (STEST3) register.
TolerANT receiver technology improves data integrity in unreliable
cabling environments where other devices would be subject to data
corruption. TolerANT receivers filter the SCSI bus signals to eliminate
unwanted transitions, without the long signal delay associated with
RC-type input filters. This improved driver and receiver technology helps
eliminate double clocking of data, the single biggest reliability issue with
SCSI operations.
The benefits of TolerANT technology include increased immunity to noise
when the signal is going HIGH, better performance due to balanced duty
cycles, and improved fast SCSI transfer rates. In addition, TolerANT SCSI
devices do not cause glitches on the SCSI bus at power-up or
power-down, so other devices on the bus are also protected from data
corruption. TolerANT technology is compatible with both the Alternative
One and Alternative Two termination schemes proposed by the American
National Standards Institute.

1.4 LSI53C875A Benefits Summary
This section of the chapter provides an overview of the LSI53C875A
features and benefits. It contains these topics:

1-4

•

SCSI Performance

•

PCI Performance

•

Integration

General Description

•

Ease of Use

•

Flexibility

•

Reliability

•

Testability

1.4.1 SCSI Performance
To improve SCSI performance, the LSI53C875A:

•

Has integrated SE transceivers.

•

Bursts up to 512 bytes across the PCI bus through its 944 byte FIFO.

•

Performs wide, Ultra SCSI synchronous transfers as fast as
40 Mbytes/s.

•

Can handle phase mismatches in SCRIPTS without interrupting the
system processor, eliminating the need for CPU intervention during
an I/O disconnect/reselect sequence.

•

Achieve Ultra SCSI transfer rates with an input frequency of 20 MHz
with the on-chip SCSI clock quadrupler.

•

Includes 4 Kbytes internal RAM for SCRIPTS instruction storage.

•

Has 31 levels of SCSI synchronous offset.

•

Supports variable block size and scatter/gather data transfers.

•

Performs sustained memory-to-memory DMA transfers to
approximately 100 Mbytes/s.

•

Minimizes SCSI I/O start latency.

•

Performs complex bus sequences without interrupts, including
restoring data pointers.

•

Reduces ISR overhead through a unique interrupt status reporting
method.

•

Uses Load/Store SCRIPTS instructions which increase performance
of data transfers to and from the chip registers without using PCI
cycles.

•

Has SCRIPTS support for 64-bit addressing.

•

Supports multithreaded I/O algorithms in SCSI SCRIPTS with fast
I/O context switching.

LSI53C875A Benefits Summary

1-5

•

Supports additional arithmetic capability with the Expanded Register
Move instruction.

1.4.2 PCI Performance
To improve PCI performance, the LSI53C875A:

•

Complies with PCI 2.2 specification.

•

Supports 32-bit 33 MHz PCI interface with 64-bit addressing.

•

Supports dual address cycles which can be generated for all
SCRIPTS for > 4 Gbyte addressability.

•

Bursts 2, 4, 8, 16, 32, 64, or 128 Dword transfers across the PCI bus.

•

Supports 32-bit word data bursts with variable burst lengths.

•

Prefetches up to 8 Dwords of SCRIPTS instructions.

•

Bursts SCRIPTS opcode fetches across the PCI bus.

•

Performs zero wait-state bus master data bursts faster than
110 Mbytes/s (@ 33 MHz).

•

Supports PCI Cache Line Size register.

•

Supports PCI Write and Invalidate, Read Line, and Read Multiple
commands.

•

Complies with PCI Bus Power Management Specification Rev 1.1.

1.4.3 Integration
Features of the LSI53C875A which ease integration include:

•

High-performance SCSI core.

•

Integrated SE transceivers.

•

Full 32-bit PCI DMA bus master.

•

Integrated SCRIPTS processor.

•

Memory-to-Memory Move instructions allow use as a third party PCI
bus DMA controller.

1.4.4 Ease of Use
The LSI53C875A provides:

1-6

General Description

•

Up to one megabyte of add-in memory support for BIOS and
SCRIPTS storage.

•

Reduced SCSI development effort.

•

Compiler-compatible with existing LSI53C7XX and LSI53C8XX
family SCRIPTS.

•

Direct connection to PCI and SCSI SE.

•

Development tools and sample SCSI SCRIPTS available.

•

Five GPIO pins.

•

Maskable and pollable interrupts.

•

Wide SCSI, A or P cable, and up to 15 devices supported.

•

Three programmable SCSI timers: Select/Reselect,
Handshake-to-Handshake, and General Purpose. The time-out
period is programmable from 100 µs to greater than 25.6 seconds.

•

Software for PC-based operating system support.

•

Support for relative jumps.

•

SCSI Selected as ID bits for responding with multiple IDs.

1.4.5 Flexibility
The LSI53C875A provides:

•

High level programming interface (SCSI SCRIPTS).

•

Ability to program local and bus flash memory.

•

Selectable 112 or 944 byte DMA FIFO for backward compatibility.

•

Tailored SCSI sequences execute from main system RAM or internal
SCRIPTS RAM.

•

Flexible programming interface to tune I/O performance or to adapt
to unique SCSI devices.

•

Support for changes in the logical I/O interface definition.

•

Low level access to all registers and all SCSI bus signals.

•

Fetch, Master, and Memory Access control pins.

•

Separate SCSI and system clocks.

LSI53C875A Benefits Summary

1-7

•

SCSI clock quadrupler bits enable Ultra SCSI transfer rates with a 20
or 40 MHz SCSI clock input.

•

Selectable IRQ pin disable bit.

•

Ability to route system clock to SCSI clock.

•

Compatible with 3.3 V and 5 V PCI.

1.4.6 Reliability
Enhanced reliability features of the LSI53C875A include:

•

2 kV ESD protection on SCSI signals.

•

Protection against bus reflections due to impedance mismatches.

•

Controlled bus assertion times (reduces RFI, improves reliability, and
eases FCC certification).

•

Latch-up protection greater than 150 mA.

•

Voltage feed-through protection (minimum leakage current through
SCSI pads).

•

High proportion (> 25%) of device pins are power or ground.

•

Power and ground isolation of I/O pads and internal chip logic.

•

TolerANT technology, which provides:
–

Active negation of SCSI Data, Parity, Request, and Acknowledge
signals for improved fast SCSI transfer rates.

–

Input signal filtering on SCSI receivers improves data integrity,
even in noisy cabling environments.

1.4.7 Testability
The LSI53C875A provides improved testability through:

1-8

•

Access to all SCSI signals through programmed I/O.

•

SCSI loopback diagnostics.

•

SCSI bus signal continuity checking.

•

Support for single step mode operation.

•

JTAG boundary scan.

General Description

Chapter 2
Functional Description

Chapter 2 is divided into the following sections:

•

Section 2.1, “PCI Functional Description”

•

Section 2.2, “SCSI Functional Description”

•

Section 2.3, “Parallel ROM Interface”

•

Section 2.4, “Serial EEPROM Interface”

•

Section 2.5, “Power Management”

The LSI53C875A PCI to Ultra SCSI Controller is composed of the
following modules:

•

32-bit PCI Interface with 64-bit addressing

•

PCI-to-Wide Ultra SCSI Controller

•

ROM/Flash Memory Controller

•

Serial EEPROM Controller

Figure 2.1 illustrates the relationship between these modules.

LSI53C875A PCI to Ultra SCSI Controller

2-1

Figure 2.1

LSI53C875A Block Diagram
PCI Bus

32 Bit PCI Interface, PCI Configuration Register

Wide Ultra SCSI Controller
4 Kbyte
SCRIPTS RAM

8 Dword SCRIPTS
Prefetch Buffer

ROM/Flash
Memory
Control
944 byte
DMA FIFO

SCSI SCRIPTS
Processor

Serial EEPROM
Controller and
Autoconfiguration

Operating
Registers

SCSI FIFO and SCSI Control Block
SE TolerANT
Drivers and Receivers

Local
Memory
Bus

JTAG

JTAG Bus

Wide Ultra
SCSI Bus

ROM/Flash
Memory Bus

2-Wire Serial
EEPROM Bus

2.1 PCI Functional Description
The LSI53C875A implements a PCI-to-Wide Ultra SCSI controller.

2.1.1 PCI Addressing
There are three physical PCI-defined address spaces:

2-2

•

PCI Configuration space.

•

I/O space for operating registers.

•

Memory space for operating registers.

Functional Description

2.1.1.1 Configuration Space
The host processor uses the PCI configuration space to initialize the
LSI53C875A through a defined set of configuration space registers. The
Configuration registers are accessible only by system BIOS during PCI
configuration cycles. The configuration space is a contiguous
256 X 8-bit set of addresses. Decoding C_BE[3:0]/ determines if a PCI
cycle is intended to access the configuration register space. The IDSEL
bus signal is a “chip select” that allows access to the configuration
register space only. A configuration read/write cycle without IDSEL is
ignored. The eight lower order address bits, AD[7:0], select a specific
8-bit register. AD[10:8] are decoded as well, but they must be zero or the
LSI53C875A does not respond. According to the PCI specification,
AD[10:8] are reserved for multifunction devices.
At initialization time, each PCI device is assigned a base address for I/O
and memory accesses. In the case of the LSI53C875A, the upper 24 bits
of the address are selected. On every access, the LSI53C875A
compares its assigned base addresses with the value on the
Address/Data bus during the PCI address phase. If the upper 24 bits
match, the access is for the LSI53C875A and the low-order eight bits
define the register being accessed. A decode of C_BE[3:0]/ determines
which registers and what type of access is to be performed.
I/O Space – The PCI specification defines I/O space as a contiguous
32-bit I/O address that is shared by all system resources, including the
LSI53C875A. Base Address Register Zero (I/O) determines which
256-byte I/O area this device occupies.
Memory Space – The PCI specification defines memory space as a
contiguous 64-bit memory address that is shared by all system
resources, including the LSI53C875A. Base Address Register One
(MEMORY) determines which 1 Kbyte memory area this device
occupies. Base Address Register Two (SCRIPTS RAM) determines the
4 Kbyte memory area occupied by SCRIPTS RAM.

2.1.2 PCI Bus Commands and Functions Supported
Bus commands indicate to the target the type of transaction the master
is requesting. Bus commands are encoded on the C_BE[3:0]/ lines
during the address phase. PCI bus commands and encoding types
appear in Table 2.1.

PCI Functional Description

2-3

Table 2.1

PCI Bus Commands and Encoding Types for the LSI53C875A

C_BE[3:0]/ Command Type

Supported as Master

Supported as Slave

0b0000

Interrupt Acknowledge

0b0001

Special Cycle

0b0010

I/O Read

Yes

0b0011

I/O Write

Yes

0b0100

Reserved

n/a

0b0101

Reserved

n/a

0b0110

Memory Read

Yes

0b0111

Memory Write

Yes

0b1000

Reserved

n/a

0b1001

Reserved

n/a

0b1010

Configuration Read

Yes

0b1011

Configuration Write

Yes

0b1100

Memory Read Multiple

Yes1

Yes (defaults to 0b0110)

0b1101

Dual Address Cycle (DAC)

Yes

0b1110

Memory Read Line

Yes1

Yes (defaults to 0b0110)

0b1111

Memory Write and Invalidate

Yes2

Yes (defaults to 0b0111)

1. See the DMA Mode (DMODE) register.
2. See the Chip Test Three (CTEST3) register.

2.1.2.1 Interrupt Acknowledge Command
The LSI53C875A does not respond to this command as a slave and it
never generates this command as a master.
2.1.2.2 Special Cycle Command
The LSI53C875A does not respond to this command as a slave and it
never generates this command as a master.

2-4

Functional Description

2.1.2.3 I/O Read Command
The I/O Read command reads data from an agent mapped in I/O
address space. All 32 address bits are decoded.
2.1.2.4 I/O Write Command
The I/O Write command writes data to an agent mapped in I/O address
space. All 32 address bits are decoded.
2.1.2.5 Reserved Command
The LSI53C875A does not respond to this command as a slave and it
never generates this command as a master.
2.1.2.6 Memory Read Command
The Memory Read command reads data from an agent mapped in the
Memory Address Space. The target is free to do an anticipatory read for
this command only if it can guarantee that such a read has no side
effects.
2.1.2.7 Memory Write Command
The Memory Write command writes data to an agent mapped in the
Memory Address Space. When the target returns “ready,” it assumes
responsibility for the coherency (which includes ordering) of the subject
data.
2.1.2.8 Configuration Read Command
The Configuration Read command reads the configuration space of each
agent. An agent is selected during a configuration access when its
IDSEL signal is asserted and AD[1:0] are 0b00.
2.1.2.9 Configuration Write Command
The Configuration Write command transfers data to the configuration
space of each agent. An agent is selected when its IDSEL signal is
asserted and AD[1:0] are 0b00.

PCI Functional Description

2-5

2.1.2.10 Memory Read Multiple Command
This command is identical to the Memory Read command except that it
additionally indicates that the master may intend to fetch more than one
cache line before disconnecting. The LSI53C875A supports PCI Memory
Read Multiple functionality and issues Memory Read Multiple commands
on the PCI bus when the Read Multiple Mode is enabled. This mode is
enabled by setting bit 2 (ERMP) of the DMA Mode (DMODE) register. If
cache mode is enabled, a Memory Read Multiple command is issued on
all read cycles, except opcode fetches, when the following conditions are
met:

•

The CLSE bit (Cache Line Size Enable, bit 7, DMA Control (DCNTL)
register) and the ERMP bit (Enable Read Multiple, bit 2, DMA Mode
(DMODE) register) are set.

•

The Cache Line Size register for each function contains a legal burst
size value (2, 4, 8, 16, 32, or 64) and that value is less than or equal
to the DMODE burst size.

•

The transfer will cross a cache line boundary.

When these conditions are met, the chip issues a Memory Read Multiple
command instead of a Memory Read during all PCI read cycles.
Burst Size Selection – The Read Multiple command reads in multiple
cache lines of data in a single bus ownership. The number of cache lines
to read is a multiple of the cache line size specified in Revision 2.2 of
the PCI specification. The logic selects the largest multiple of the cache
line size based on the amount of data to transfer, with the maximum
allowable burst size determined from the DMA Mode (DMODE) burst size
bits, and the Chip Test Five (CTEST5), bit 2.
2.1.2.11 Dual Address Cycle (DAC) Command
The LSI53C875A performs DACs when 64-bit addressing is required.
Refer to the PCI 2.2 specification. If any of the selector registers contain
a nonzero value, a DAC is generated. See 64-bit SCRIPTS Selectors in
Chapter 4, “Registers,” for additional information.
2.1.2.12 Memory Read Line Command
This command is identical to the Memory Read command, except that it
additionally indicates that the master intends to fetch a complete cache

2-6

Functional Description

line. This command is intended for use with bulk sequential data transfers
where the memory system and the requesting master might gain some
performance advantage by reading to a cache line boundary rather than
a single memory cycle. The Read Line function in the LSI53C875A takes
advantage of the PCI 2.2 specification regarding issuing this command.
If the cache mode is disabled, Read Line commands are not issued.
If the cache mode is enabled, a Read Line command is issued on all
read cycles, except nonprefetch opcode fetches, when the following
conditions are met:

•

The CLSE (Cache Line Size Enable, bit 7, DMA Control (DCNTL)
register) and ERL (Enable Read Line, bit 3, DMA Mode (DMODE)
register) bits are set.

•

The Cache Line Size register must contain a legal burst size value
in Dwords (2, 4, 8, 16, 32, 64, or 128) and that value is less than or
equal to the DMA Mode (DMODE) burst size.

•

The transfer will cross a Dword boundary but not a cache line
boundary.

When these conditions are met, the chip issues a Read Line command
instead of a Memory Read during all PCI read cycles. Otherwise, it
issues a normal Memory Read command.
Read Multiple with Read Line Enabled – When both the Read Multiple
and Read Line modes are enabled, the Read Line command is not
issued if the above conditions are met. Instead, a Read Multiple
command is issued, even though the conditions for Read Line are met.
If the Read Multiple mode is enabled and the Read Line mode is
disabled, Read Multiple commands are issued if the Read Multiple
conditions are met.

PCI Functional Description

2-7

2.1.2.13 Memory Write and Invalidate Command
The Memory Write and Invalidate command is identical to the Memory
Write command, except that it additionally guarantees a minimum
transfer of one complete cache line; that is to say, the master intends to
write all bytes within the addressed cache line in a single PCI transaction
unless interrupted by the target. This command requires implementation
of the PCI Cache Line Size register at address 0x0C in PCI configuration
space. The LSI53C875A enables Memory Write and Invalidate cycles
when bit 0 (WRIE) in the Chip Test Three (CTEST3) register and bit 4
(WIE) in the PCI Command register are set. When the following
conditions are met, Memory Write and Invalidate commands are issued:
1. The CLSE bit (Cache Line Size Enable, bit 7, DMA Control (DCNTL)
register), WRIE bit (Write and Invalidate Enable, bit 0, Chip Test
Three (CTEST3) register), and PCI configuration Command register,
bit 4 are set.
2. The Cache Line Size register contains a legal burst size value in
Dwords (2, 4, 8, 16, 32, 64, or 128) and that value is less than or
equal to the DMA Mode (DMODE) burst size.
3. The chip has enough bytes in the DMA FIFO to complete at least
one full cache line burst.
4. The chip is aligned to a cache line boundary.
When these conditions are met, the LSI53C875A issues a Memory Write
and Invalidate command instead of a Memory Write command during all
PCI write cycles.
Multiple Cache Line Transfers – The Memory Write and Invalidate
command can write multiple cache lines of data in a single bus
ownership. The chip issues a burst transfer as soon as it reaches a
cache line boundary. The size of the transfer is not automatically the
cache line size, but rather a multiple of the cache line size specified in
Revision 2.2 of the PCI specification. The logic selects the largest
multiple of the cache line size based on the amount of data to transfer,
with the maximum allowable burst size determined from the DMA Mode
(DMODE) burst size bits, and Chip Test Five (CTEST5), bit 2. If multiple
cache line size transfers are not desired, set the DMA Mode (DMODE)
burst size to exactly the cache line size and the chip only issues single
cache line transfers.

2-8

Functional Description

After each data transfer, the chip re-evaluates the burst size based on
the amount of remaining data to transfer and again selects the highest
possible multiple of the cache line size, and no larger than the DMA
Mode (DMODE) burst size. The most likely scenario of this scheme is
that the chip selects the DMA Mode (DMODE) burst size after alignment,
and issues bursts of this size. The burst size is, in effect, throttled down
toward the end of a long Memory Move or Block Move transfer until only
the cache line size burst size is left. The chip finishes the transfer with
this burst size.
Latency – In accordance with the PCI specification, the latency timer is
ignored when issuing a Memory Write and Invalidate command such that
when a latency time-out occurs, the LSI53C875A continues to transfer
up to a cache line boundary. At that point, the chip relinquishes the bus,
and finishes the transfer at a later time using another bus ownership. If
the chip is transferring multiple cache lines it continues to transfer until
the next cache boundary is reached.
PCI Target Retry – During a Memory Write and Invalidate transfer, if the
target device issues a retry (STOP with no TRDY/, indicating that no data
was transferred), the chip relinquishes the bus and immediately tries to
finish the transfer on another bus ownership. The chip issues another
Memory Write and Invalidate command on the next ownership, in
accordance with the PCI specification.
PCI Target Disconnect – During a Memory Write and Invalidate
transfer, if the target device issues a disconnect the LSI53C875A
relinquishes the bus and immediately tries to finish the transfer on
another bus ownership. The chip does not issue another Memory Write
and Invalidate command on the next ownership unless the address is
aligned.

2.1.3 PCI Cache Mode
The LSI53C875A supports the PCI specification for an 8-bit Cache Line
Size register located in the PCI configuration space. The Cache Line
Size register provides the ability to sense and react to nonaligned
addresses corresponding to cache line boundaries. In conjunction with
the Cache Line Size register, the PCI commands Memory Read Line,
Memory Read Multiple, and Memory Write and Invalidate are each

PCI Functional Description

2-9

software enabled or disabled to allow the user full flexibility in using these
commands.
2.1.3.1 Enabling Cache Mode
In order to enable the cache logic to issue PCI cache commands
(Memory Read Line, Memory Read Multiple, and Memory Write and
Invalidate) on any given PCI master operation the following conditions
must be met:

•

The Cache Line Size Enable bit in the DMA Control (DCNTL) register
must be set.

•

The PCI Cache Line Size register must contain a valid binary cache
size, i.e. 2, 4, 8, 16, 32, 64, or 128 Dwords. Only these values are
considered valid cache sizes.

•

The programmed burst size (in Dwords) must be equal to or greater
than the Cache Line Size register. The DMA Mode (DMODE) register
bits [7:6] and Chip Test Five (CTEST5) bit 2 are the burst length bits.

•

The part must be doing a PCI Master transfer. The following PCI
Master transactions do not utilize the PCI cache logic and thus no
PCI cache command is issued during these types of cycles: a
nonprefetch SCRIPTS fetch, a Load/Store data transfer, or a data
flush operation. All other types of PCI Master transactions will utilize
the PCI cache logic.

The above conditions must be met for the cache logic to control the type
of PCI cache command that is issued, along with any alignment that may
be necessary during write operations. If these conditions are not met for
any given PCI Master transaction, a Memory Read or Memory Write is
issued and no cache write alignment is done.
2.1.3.2 Issuing Cache Commands
In order to issue each type of PCI cache command, the corresponding
enable bit must be set (2 bits in the case of Memory Write and
Invalidate). These bits are detailed below:

•

2-10

To issue Memory Read Line commands, the Read Line enable bit in
the DMA Mode (DMODE) register must be set.

Functional Description

•

To issue Memory Read Multiple commands, the Read Multiple
enable bit in the DMA Mode (DMODE) register must be set.

•

To issue Memory Write and Invalidate commands, both the Write and
Invalidate enables in the Chip Test Three (CTEST3) register and the
PCI configuration command register must be set.

If the corresponding cache command being issued is not enabled then
the cache logic falls back to the next command enabled. Specifically, if
Memory Read Multiple is not enabled and Memory Read Lines are, read
lines are issued in place of read multiple. If no cache commands are
enabled, cache write alignment still occurs but no cache commands are
issued, only memory reads and memory writes.
2.1.3.3 Memory Read Caching
The type of Memory Read command issued depends on the starting
location of the transfer and the number of bytes being transferred. During
reads, no cache alignment is done (this is not required nor optimal per
PCI 2.2 specification) and reads will always be either a programmed
burst length in size, as set in the DMA Mode (DMODE) and Chip Test
Three (CTEST3) registers. In the case of a transfer which is smaller than
the burst length, all bytes for that transfer are read in one PCI burst
transaction. If the transfer will cross a Dword boundary (A[1:0] = 0b00) a
Memory Read Line command is issued. When the transfer will cross a
cache boundary (depends on cache line size programmed into the PCI
configuration register), a Memory Read Multiple command is issued. If a
transfer will not cross a Dword or cache boundary or if cache mode is
not enabled a Memory Read command is issued.
2.1.3.4 Memory Write Caching
Writes are aligned in a single burst transfer to get to a cache boundary.
At that point, Memory Write and Invalidate commands are issued and
continue at the burst length programmed into the DMA Mode (DMODE)
register. Memory Write and Invalidate commands are issued as long as
the remaining byte count is greater than the Memory Write and Invalidate
threshold. When the byte count goes below this threshold, a single
Memory Write burst is issued to complete the transfer. The general
pattern for PCI writes is:

•

A single Memory Write to align to a cache boundary.

PCI Functional Description

2-11

•

Multiple Memory Write and Invalidates.

•

A single data residual Memory Write to complete the transfer.

Table 2.2 describes PCI cache mode alignment.
Table 2.2

PCI Cache Mode Alignment
Host Memory
A

00h

04h
08h
C

0Ch

10h
14h
18h
1Ch

20h
24h
28h
2Ch
F

30h
34h
38h
3Ch

40h
44h
48h
4Ch
H

50h
54h
58h
5Ch
60h

2-12

Functional Description

2.1.3.5 Examples:
MR = Memory Read, MRL = Memory Read Line, MRM = Memory Read
Multiple, MW = Memory Write, MWI = Memory Write and Invalidate.
Read Example 1 –
Burst = 4 Dwords, Cache Line Size = 4 Dwords:
A to B:

MRL (6 bytes)

A to C:

MRL (13 bytes)

A to D:

MRL (15 bytes)
MR (2 bytes)

C to D:

MRM (5 bytes)

C to E:

MRM (15 bytes)
MRM (6 bytes)

D to F:

MRL (15 bytes)
MRL (16 bytes)
MR (1 byte)

A to H:

MRL (15 bytes)
MRL (16 bytes)
MRL (16 bytes)
MRL (16 bytes)
MRL (16 bytes)
MR (2 bytes)

A to G:

MRL (15 bytes)
MRL (16 bytes)
MRL (16 bytes)
MRL (16 bytes)
MR (3 bytes)

Read Example 2 –
Burst = 8 Dwords, Cache Line Size = 4 Dwords:
A to B:

MRL (6 bytes)

A to C:

MRL (13 bytes)

A to D:

MRM (17 bytes)

C to D:

MRM (5 bytes)

PCI Functional Description

2-13

C to E:

MRM (21 bytes)

D to F:

MRM (31 bytes)
MR (1 byte)

A to H:

MRM (31 bytes)
MRM (32 bytes)
MRM (18 bytes)

A to G:

MRM (31 bytes)
MRM (32 bytes)
MR (3 bytes)

Read Example 3 –
Burst = 16 Dwords, Cache Line Size = 8 Dwords:
A to B:

MRL (6 bytes)

A to C:

MRL (13 bytes)

A to D:

MRL (17 bytes)

C to D:

MRL (5 bytes)

C to E:

MRM (21 bytes)

D to F:

MRM (32 bytes)

A to H:

MRM (63 bytes)
MRL (16 bytes)
MRM (2 bytes)

A to G:

2 transfers, MRM (63 bytes), MR (3 bytes)

Write Example 1 –
Burst = 4 Dwords, Cache Line Size = 4 Dwords:

2-14

A to B:

MW (6 bytes)

A to C:

MW (13 bytes)

A to D:

MW (17 bytes)

C to D:

MW (5 bytes)

C to E:

MW (3 bytes)
MWI (16 bytes)
MW (2 bytes)

Functional Description

D to F:

MW (15 bytes)
MWI (16 bytes)
MW (1 byte)

A to H:

MW (15 bytes)
MWI (16 bytes)
MWI (16 bytes)
MWI (16 bytes)
MWI (16 bytes)
MW (2 bytes)

A to G:

MW (15 bytes)
MWI (16 bytes)
MWI (16 bytes)
MWI (16 bytes)
MW (3 bytes)

Write Example 2 –
Burst = 8 Dwords, Cache Line Size = 4 Dwords:
A to B:

MW (6 bytes)

A to C:

MW (13 bytes)

A to D:

MW (17 bytes)

C to D:

MW (5 bytes)

C to E:

MW (3 bytes)
MWI (16 bytes)
MW (2 bytes)

D to F:

MW (15 bytes)
MWI (16 bytes)
MW (1 byte)

A to H:

MW (15 bytes)
MWI (32 bytes)
MWI (32 bytes)
MW (2 bytes)

A to G:

MW (15 bytes)
MWI (32 bytes)
MWI (16 bytes)
MW (3 bytes)

PCI Functional Description

2-15

Write Example 3 –
Burst = 16 Dwords, Cache Line Size = 8 Dwords:
A to B:

MW (6 bytes)

A to C:

MW (13 bytes)

A to D:

MW (17 bytes)

C to D:

MW (5 bytes)

C to E:

MW (21 bytes)

D to F:

MW (32 bytes)

A to H:

MW (15 bytes)
MWI (64 bytes)
MW (2 bytes)

A to G:

MW (15 bytes)
MWI (32 bytes)
MW (18 bytes)

2.1.3.6 Memory-to-Memory Moves
Memory-to-Memory Moves also support PCI cache commands, as
described above, with one limitation. Memory Write and Invalidate on
Memory-to-Memory Move writes are only supported if the source and
destination address are quad word aligned. If the source and destination
are not quad word aligned (that is, Source address [2:0] == Destination
Address [2:0]), write aligning is not performed and Memory Write and
Invalidate commands are not issued. The LSI53C875A is little endian
only.

2.2 SCSI Functional Description
The LSI53C875A provides an Ultra SCSI controller that supports an
8-bit or 16-bit bus. The controller supports Wide Ultra SCSI synchronous
transfer rates up to 40 Mbytes/s. The SCSI core can be programmed with
SCSI SCRIPTS, making it easy to “fine tune” the system for specific
mass storage devices or Ultra SCSI requirements.
The LSI53C875A offers low level register access or a high-level control
interface. Like first generation SCSI devices, the LSI53C875A is

2-16

Functional Description

accessed as a register-oriented device. Error recovery and/or diagnostic
procedures use the ability to sample and/or assert any signal on the
SCSI bus. In support of SCSI loopback diagnostics, the SCSI core may
perform a self-selection and operate as both an initiator and a target.
The LSI53C875A is controlled by the integrated SCRIPTS processor
through a high-level logical interface. Commands controlling the SCSI
core are fetched out of the main host memory or local memory. These
commands instruct the SCSI core to Select, Reselect, Disconnect, Wait
for a Disconnect, Transfer Information, Change Bus Phases and, in
general, implement all aspects of the SCSI protocol. The SCRIPTS
processor is a special high-speed processor optimized for SCSI protocol.

2.2.1 SCRIPTS Processor
The SCSI SCRIPTS processor allows both DMA and SCSI commands
to be fetched from host memory or internal SCRIPTS RAM. Algorithms
written in SCSI SCRIPTS control the actions of the SCSI and DMA
cores. The SCRIPTS processor executes complex SCSI bus sequences
independently of the host= CPU.
Algorithms may be designed to tune SCSI bus performance, to adjust to
new bus device types (such as scanners, communication gateways, etc.),
or to incorporate changes in the SCSI-2 or SCSI-3 logical bus definitions
without sacrificing I/O performance. SCSI SCRIPTS are hardware
independent, so they can be used interchangeably on any host or CPU
system bus. SCSI SCRIPTS handle conditions like Phase Mismatch.
2.2.1.1 Phase Mismatch Handling in SCRIPTS
The LSI53C875A can handle phase mismatches due to drive
disconnects without needing to interrupt the processor. The primary goal
of this logic is to completely eliminate the need for CPU intervention
during an I/O disconnect/reselect sequence.
Storing the appropriate information to later restart the I/O can be done
through SCRIPTS, eliminating the need for processor intervention during
an I/O disconnect/reselect sequence. Calculations are performed such
that the appropriate information is available to SCRIPTS so that an I/O
state can be properly stored for restart later.

SCSI Functional Description

2-17

The Phase Mismatch Jump logic powers up disabled and must be
enabled by setting the Phase Mismatch Jump Enable bit (ENPMJ, bit 7
in the Chip Control 0 (CCNTL0) register).
Utilizing the information supplied in the Phase Mismatch Jump Address
1 (PMJAD1) and Phase Mismatch Jump Address 2 (PMJAD2) registers,
described in Chapter 4, “Registers,” SCRIPTS handles all overhead
involved in a disconnect/reselect sequence with a modest number of
instructions.

2.2.2 Internal SCRIPTS RAM
The LSI53C875A has 4 Kbyte (1024 x 32 bits) of internal, general
purpose RAM. The RAM is designed for SCRIPTS program storage, but
is not limited to this type of information. When the chip fetches SCRIPTS
instructions or Table Indirect information from the internal RAM, these
fetches remain internal to the chip and do not use the PCI bus. Other
types of access to the RAM by the chip, except Load/Store, use the PCI
bus, as if they were external accesses. The SCRIPTS RAM powers up
enabled by default.
The RAM can be relocated by the PCI system BIOS anywhere in the
32-bit address space. The Base Address Register Two (SCRIPTS RAM)
in the PCI configuration space contains the base address of the internal
RAM. To simplify loading of the SCRIPTS instructions, the base address
of the RAM appears in the Scratch Register B (SCRATCHB) register
when bit 3 of the Chip Test Two (CTEST2) register is set. The RAM is
byte accessible from the PCI bus and is visible to any bus mastering
device on the bus. External accesses to the RAM (by the CPU) follow
the same timing sequence as a standard slave register access, except
that the required target wait-states drop from 5 to 3.
A complete set of development tools is available for writing custom
drivers with SCSI SCRIPTS. For more information on the SCSI SCRIPTS
instructions supported by the LSI53C875A, see Chapter 5, “SCSI
SCRIPTS Instruction Set.”

2-18

Functional Description

2.2.3 64-Bit Addressing in SCRIPTS
The LSI53C875A has a 32-bit PCI interface which provides 64-bit
address capability in the initiator mode.
DACs can be generated for all SCRIPTS operations. There are six
selector registers which hold the upper Dword of a 64-bit address. All but
one of these is static and requires manual loading using a CPU access,
a Load/Store instruction, or a Memory Move instruction. One of the
selector registers is dynamic and is used during 64-bit direct block moves
only. All selectors default to zero, meaning the LSI53C875A powers-up
in a state where only Single Address Cycles (SACs) are generated.
When any of the selector registers are written to a nonzero value, DACs
are generated.
Direct, Table Indirect and Indirect Block moves, Memory-to-Memory
Moves, Load and Store instructions, and jumps are all instructions with
64-bit address capability.
Crossing the 4 Gbyte boundary on any one SCRIPTS operation is not
permitted and software needs to take care that any given SCRIPTS
operation will not cross the 4 Gbyte boundary.

2.2.4 Hardware Control of SCSI Activity LED
The LSI53C875A has the ability to control a LED through the GPIO_0
pin to indicate that it is connected to the SCSI bus. Formerly this function
was done by a software driver.
When bit 5 (LED_CNTL) in the General Purpose Pin Control Zero
(GPCNTL0) register is set and bit 6 (Fetch Enable) in the General
Purpose Pin Control Zero (GPCNTL0) register is cleared and the
LSI53C875A is not performing an EEPROM autodownload, then bit 3
(CON) in the Interrupt Status Zero (ISTAT0) register is presented at the
GPIO_0 pin.
The CON (Connected) bit in Interrupt Status Zero (ISTAT0) is set anytime
the LSI53C875A is connected to the SCSI bus either as an initiator or a
target. This will happen after the LSI53C875A has successfully
completed a selection or when it has successfully responded to a
selection or reselection. It will also be set when the LSI53C875A wins
arbitration in low level mode.

SCSI Functional Description

2-19

2.2.5 Designing an Ultra SCSI System
Since Ultra SCSI is based on existing SCSI standards, it can use existing
driver programs as long as the software is able to negotiate for Ultra
SCSI synchronous transfer rates. Additional software modifications are
needed to take advantage of the new features in the LSI53C875A.
For additional information on Ultra SCSI, refer to the SPI-2 working
document which is available from the SCSI BBS referenced at the
beginning of this manual. Chapter 6, “Electrical Specifications,” contains
Ultra SCSI timing information. In addition to the guidelines in the draft
standard, make the following software and hardware adjustments to
accommodate Ultra SCSI transfers:

•

Set the Ultra Enable bit to enable Ultra SCSI transfers.

•

Set the TolerANT Enable bit, bit 7 in the SCSI Test Three (STEST3)
register, whenever the Ultra Enable bit is set.

•

Do not extend the SREQ/SACK filtering period with SCSI Test Two
(STEST2) bit 1. When the Ultra Enable bit is set, the filtering period
is fixed at 15 ns for Ultra SCSI, regardless of the value of the
SREQ/SACK Filtering bit.

•

Use the SCSI clock quadrupler.
A 20 or 40 MHz input must be supplied if using the SCSI clock
quadrupler for an Ultra design.

2.2.5.1 Using the SCSI Clock Quadrupler
The LSI53C875A can quadruple the frequency of a 20 MHz SCSI clock,
allowing the system to perform Ultra SCSI transfers. This option is user
selectable with bit settings in the SCSI Test One (STEST1), SCSI Test
Three (STEST3), and SCSI Control Three (SCNTL3) registers. At
power-on or reset, the quadrupler is disabled and powered down. Follow
these steps to use the clock quadrupler:
Step 1. Set the SCLK Quadrupler Enable bit (SCSI Test One
(STEST1), bit 3).
Step 2. Poll bit 5 of the SCSI Test Four (STEST4) register.
The LSI53C875A sets this bit as soon as it locks in the
quadrupled frequency. The frequency lockup takes
approximately 100 µs.

2-20

Functional Description

Step 3. Halt the SCSI clock by setting the Halt SCSI Clock bit (SCSI
Test Three (STEST3), bit 5).
Step 4. Set the clock conversion factor using the SCF and CCF fields
in the SCSI Control Three (SCNTL3) register.
Step 5. Set the SCLK Quadrupler Select bit (SCSI Test One (STEST1),
bit 2).
Step 6. Clear the Halt SCSI Clock bit.

2.2.6 Prefetching SCRIPTS Instructions
When enabled by setting the Prefetch Enable bit (bit 5) in the DMA
Control (DCNTL) register, the prefetch logic in the LSI53C875A fetches
8 Dwords of instructions. The prefetch logic automatically determines the
maximum burst size that it can perform, based on the burst length as
determined by the values in the DMA Mode (DMODE) register. If the unit
cannot perform bursts of at least four Dwords, it disables itself. While the
chip is prefetching SCRIPTS instructions, it will use PCI cache
commands Memory Read Line, and Memory Read Multiple, if PCI
caching is enabled.
Note:

This feature is only useful if fetching SCRIPTS instructions
from main memory. Due to the short access time of
SCRIPTS RAM, prefetching is not necessary when fetching
instructions from this memory.

The LSI53C875A may flush the contents of the prefetch unit under
certain conditions, listed below, to ensure that the chip always operates
from the most current version of the SCRIPTS instruction. When one of
these conditions apply, the contents of the prefetch unit are automatically
flushed.

•

On every Memory Move instruction. The Memory Move instruction is
often used to place modified code directly into memory. To make
sure that the chip executes all recent modifications, the prefetch unit
flushes its contents and loads the modified code every time an
instruction is issued. To avoid inadvertently flushing the prefetch unit
contents, use the No Flush option for all Memory Move operations
that do not modify code within the next 8 Dwords. For more
information on this instruction refer to Chapter 5, “SCSI SCRIPTS
Instruction Set.”

SCSI Functional Description

2-21

•

On every Store instruction. The Store instruction may also be used
to place modified code directly into memory. To avoid inadvertently
flushing the prefetch unit contents use the No Flush option for all
Store operations that do not modify code within the next 8 Dwords.

•

On every write to the DMA SCRIPTS Pointer (DSP) register.

•

On all Transfer Control instructions when the transfer conditions are
met. This is necessary because the next instruction to execute is not
the sequential next instruction in the prefetch unit.

•

When the Prefetch Flush bit (DMA Control (DCNTL) register, bit 6)
is set. The unit flushes whenever this bit is set. The bit is selfclearing.

2.2.7 Opcode Fetch Burst Capability
Setting the Burst Opcode Fetch Enable bit (bit 1) in the DMA Mode
(DMODE) register (0x38) causes the LSI53C875A to burst in the first two
Dwords of all instruction fetches. If the instruction is a Memory-toMemory Move, the third Dword is accessed in a separate ownership. If
the instruction is an indirect type, the additional Dword is accessed in a
subsequent bus ownership. If the instruction is a Table Indirect Block
Move, the chip uses two accesses to obtain the four Dwords required, in
two bursts of two Dwords each.
Note:

This feature is only useful if Prefetching is disabled and
SCRIPTS instructions are fetched from main memory. Due
to the short SCRIPTS RAM access time, burst opcode
fetching is not necessary when fetching instructions from
this memory.

2.2.8 Load and Store Instructions
The LSI53C875A supports the Load and Store instruction type, which
simplifies the movement of data between memory and the internal chip
registers. It also enables the chip to transfer bytes to addresses relative
to the Data Structure Address (DSA) register. Load and Store data
transfers to or from the SCRIPTS RAM will remain internal to the chip
and will not generate PCI bus cycles. While a Load/Store to or from
SCRIPTS RAM is occurring, any external PCI slave cycles that occur are
retried on the PCI bus. This feature can be disabled by setting the DILS
bit in the Chip Control 0 (CCNTL0) register. For more information on the

2-22

Functional Description

Load and Store instructions, refer to Chapter 5, “SCSI SCRIPTS
Instruction Set.”

2.2.9 JTAG Boundary Scan Testing
The LSI53C875A includes support for JTAG boundary scan testing in
accordance with the IEEE 1149.1 specification with one exception, which
is explained in this section. This device accepts all required boundary
scan instructions including the optional CLAMP, HIGH-Z, and IDCODE
instructions.
The LSI53C875A uses an 8-bit instruction register to support all
boundary scan instructions. The data registers included in the device are
the Boundary Data register, the IDCODE register, and the Bypass
register. This device can handle a 10 MHz TCLK frequency for TDO and
TDI.
Due to design constraints, the RST/ pin (system reset) always 3-states
the SCSI pins when it is asserted. Boundary scan logic does not control
this action, and this is not compliant with the specification. There are two
solutions that resolve this issue:
1. Use the RST/ pin as a boundary scan compliance pin. When the pin
is deasserted, the device is boundary scan compliant and when
asserted, the device is noncompliant. To maintain compliance the
RST/ pin must be driven HIGH.
2. When RST/ is asserted during boundary scan testing the expected
output on the SCSI pins must be the HIGH-Z condition, and not what
is contained in the boundary scan data registers for the SCSI pin
output cells.

2.2.10 SCSI Loopback Mode
The LSI53C875A loopback mode allows testing of both initiator and
target functions and, in effect, lets the chip communicate with itself.
When the Loopback Enable bit is set in the SCSI Test Two (STEST2)
register, bit 4, the LSI53C875A allows control of all SCSI signals whether
the chip is operating in the initiator or target mode. For more information
on this mode of operation refer to the LSI Logic SCSI SCRIPTS
Processor Programming Guide.

SCSI Functional Description

2-23

2.2.11 Parity Options
The LSI53C875A implements a flexible parity scheme that allows control
of the parity sense, allows parity checking to be turned on or off, and has
the ability to deliberately send a byte with bad parity over the SCSI bus
to test parity error recovery procedures. Table 2.3 defines the bits that
are involved in parity control and observation. Table 2.4 describes the
parity control function of the Enable Parity Checking and Assert SCSI
Even Parity bits in the SCSI Control One (SCNTL1) register, bit 2.
Table 2.5 describes the options available when a parity error occurs.
Figure 2.2 shows where parity checking is done in the LSI53C875A.

2-24

Functional Description

Table 2.3

Bits Used for Parity Control and Generation

Bit Name

Location

Description

Assert SATN/ on
Parity Errors

SCSI Control Zero
(SCNTL0), Bit 1

Causes the LSI53C875A to automatically assert SATN/
when it detects a SCSI parity error while operating as an
initiator.

Enable Parity
Checking

SCSI Control Zero
(SCNTL0), Bit 3

Enables the LSI53C875A to check for parity errors. The
LSI53C875A checks for odd parity.

Assert Even SCSI
Parity

SCSI Control One
(SCNTL1), Bit 2

Determines the SCSI parity sense generated by the
LSI53C875A to the SCSI bus.

Disable Halt on
SATN/ or a Parity
Error (Target Mode
Only)

SCSI Control One
(SCNTL1), Bit 5

Causes the LSI53C875A not to halt operations when a
parity error is detected in target mode.

Enable Parity Error
Interrupt

SCSI Interrupt
Enable Zero
(SIEN0), Bit 0

Determines whether the LSI53C875A generates an
interrupt when it detects a SCSI parity error.

Parity Error

SCSI Interrupt
Status Zero
(SIST0), Bit 0

This status bit is set whenever the LSI53C875A detects a
parity error on the SCSI bus.

Status of SCSI
Parity Signal

SCSI Status Zero
(SSTAT0), Bit 0

This status bit represents the active HIGH current state of
the SCSI SDP0 parity signal.

SCSI SDP1 Signal

SCSI Status Two
(SSTAT2), Bit 0

This bit represents the active HIGH current state of the
SCSI SDP1 parity signal.

Latched SCSI Parity

SSTAT 2, Bit 3 and
SCSI Status One
(SSTAT1), Bit 3

These bits reflect the SCSI odd parity signal
corresponding to the data latched into the SCSI Input
Data Latch (SIDL) register.

Master Parity Error
Enable

Chip Test Four
(CTEST4), Bit 3

Enables parity checking during PCI master data phases.

Master Data Parity
Error

DMA Status
(DSTAT), Bit 6

Set when the LSI53C875A, as a PCI master, detects a
target device signaling a parity error during a data phase.

Master Data Parity
Error Interrupt
Enable

DMA Interrupt
Enable (DIEN),
Bit 6

By clearing this bit, a Master Data Parity Error does not
cause assertion of INTA/ (or INTB/), but the status bit is
set in the DMA Status (DSTAT) register.

SCSI Functional Description

2-25

Table 2.4

SCSI Parity Control

EPC1

ASEP2

Does not check for parity errors. Parity is generated when sending
SCSI data. Asserts odd parity when sending SCSI data.

Does not check for parity errors. Parity is generated when sending
SCSI data. Asserts even parity when sending SCSI data.

Checks for odd parity on SCSI data received. Parity is generated when
sending SCSI data. Asserts odd parity when sending SCSI data.

Checks for odd parity on SCSI data received. Parity is generated when
sending SCSI data. Asserts even parity when sending SCSI data.

Description

1. EPC = Enable Parity Checking (bit 3 SCSI Control Zero (SCNTL0)).
2. ASEP = Assert SCSI Even Parity (bit 2 SCSI Control One (SCNTL1)).

Table 2.5

SCSI Parity Errors and Interrupts

DHP1

PAR2

Halts when a parity error occurs in the target or initiator mode and does
NOT generate an interrupt.

Halts when a parity error occurs in the target mode and generates an
interrupt in the target or initiator mode.

Does not halt in target mode when a parity error occurs until the end
of the transfer. An interrupt is not generated.

Does not halt in target mode when a parity error occurs until the end
of the transfer. An interrupt is generated.

Description

1. DHP = Disable Halt on SATN/ or Parity Error (bit 5 SCSI Control One (SCNTL1)).
2. PAR = Parity Error (bit 0 SCSI Interrupt Enable Zero (SIEN0)).

2-26

Functional Description

Figure 2.2

Parity Checking/Generation

Asynchronous
SCSI Send

Asynchronous
SCSI Receive

Synchronous
SCSI Send

Synchronous
SCSI Receive

PCI Interface**

G
DMA FIFO*
(64 bits X 118)

DMA FIFO*
(64 bits X 118)

G
DMA FIFO*
(64 bits X 118)

X
SIDL Register*

SODL Register*

X
SCSI Interface**

SCSI Interface**

SCSI FIFO**
(8 or 16 bits x 31)

SODR Register*

SCSI Interface**

S
X = Check parity
G = Generate 32-bit even PCI parity
S = Generate 8-bit odd SCSI parity

SCSI Interface**

* = No parity protection
** = Parity protected

2.2.12 DMA FIFO
The DMA FIFO is 8 bytes wide by 118 transfers deep. The DMA FIFO is
illustrated in Figure 2.3. The default DMA FIFO size is 112 bytes to
assure compatibility with older products in the LSI53C8XX family.
The DMA FIFO size may be set to 944 bytes by setting the DMA FIFO
Size bit, bit 5, in the Chip Test Five (CTEST5) register.

SCSI Functional Description

2-27

Figure 2.3

DMA FIFO Sections
8 Bytes Wide

..
.

118
Transfers
Deep

8 Bits
8 Bits
8 Bits
8 Bits
8 Bits
8 Bits
8 Bits
8 Bits
Byte Lane 7 Byte Lane 6 Byte Lane 5 Byte Lane 4 Byte Lane 3 Byte Lane 2 Byte Lane 1 Byte Lane 0

The LSI53C875A automatically supports misaligned DMA transfers. A
944-byte FIFO allows the LSI53C875A to support 2, 4, 8, 16, 32, 64, or
128 Dword bursts across the PCI bus interface.
2.2.12.1 Data Paths
The data path through the LSI53C875A is dependent on whether data is
being moved into or out of the chip, and whether SCSI data is being
transferred asynchronously or synchronously.
Figure 2.4 shows how data is moved to/from the SCSI bus in each of the
different modes.

2-28

Functional Description

Figure 2.4

LSI53C875A Host Interface SCSI Data Paths

Asynchronous
SCSI Send

Asynchronous
SCSI Receive

Synchronous
SCSI Send

Synchronous
SCSI Receive

PCI Interface**

DMA FIFO*
(8 Bytes x 118)

SWIDE Register

SODL Register*

SIDL Register*

SODL Register*

SCSI FIFO**
(1 or 2 Bytes x 31)

SCSI Interface**

SODR Register*

SCSI Interface**

* = No parity protection
** = Parity protected

The following steps determine if any bytes remain in the data path when
the chip halts an operation:
Asynchronous SCSI Send –
Step 1. If the DMA FIFO size is set to 112 bytes (bit 5 of the Chip Test
Five (CTEST5) register cleared), look at the DMA FIFO
(DFIFO) and DMA Byte Counter (DBC) registers and calculate
if there are bytes left in the DMA FIFO. To make this calculation,
subtract the seven least significant bits of the DBC register from
the 7-bit value of the DFIFO register. AND the result with 0x7F
for a byte count between zero and 112.
If the DMA FIFO size is set to 944 bytes (bit 5 of the Chip Test
Five (CTEST5) register is set), subtract the 10 least significant

SCSI Functional Description

2-29

bits of the DBC register from the 10-bit value of the DMA FIFO
Byte Offset Counter, which consists of bits [1:0] in the CTEST5
register and bits [7:0] of the DMA FIFO register. AND the result
with 0x3FF for a byte count between zero and 944.
Step 2. Read bit 5 in the SCSI Status Zero (SSTAT0) and SCSI Status
Two (SSTAT2) registers to determine if any bytes are left in the
SCSI Output Data Latch (SODL) register. If bit 5 is set in the
SSTAT0 or SSTAT2 register, then the least significant byte or
the most significant byte in the SODL register is full,
respectively. Checking this bit also reveals bytes left in the
SODL register from a Chained Move operation with an odd byte
count.
Synchronous SCSI Send –
Step 1. If the DMA FIFO size is set to 112 bytes (bit 5 of the Chip Test
Five (CTEST5) register cleared), look at the DFIFO and DBC
registers and calculate if there are bytes left in the DMA FIFO.
To make this calculation, subtract the seven least significant bits
of the DMA Byte Counter (DBC) register from the 7-bit value of
the DMA FIFO (DFIFO) register. AND the result with 0x7F for
a byte count between zero and 112.
If the DMA FIFO size is set to 944 bytes (bit 5 of the CTEST5
register is set), subtract the 10 least significant bits of the DBC
register from the 10-bit value of the DMA FIFO Byte Offset
Counter, which consists of bits [1:0] in the CTEST5 register and
bits [7:0] of the DMA FIFO register. AND the result with 0x3FF
for a byte count between zero and 944.
Step 2. Read bit 5 in the SCSI Status Zero (SSTAT0) and SCSI Status
Two (SSTAT2) registers to determine if any bytes are left in the
SCSI Output Data Latch (SODL) register. If bit 5 is set in the
SSTAT0 or SSTAT2 register, then the least significant byte or
the most significant byte in the SODL register is full,
respectively. Checking this bit also reveals bytes left in the
SODL register from a Chained Move operation with an odd byte
count.
Step 3. Read bit 6 in the SCSI Status Zero (SSTAT0) and SCSI Status
Two (SSTAT2) registers to determine if any bytes are left in the
SODR register (a hidden buffer register which is not
accessible). If bit 6 is set in the SSTAT0 or SSTAT2 register,

2-30

Functional Description

then the least significant byte or the most significant byte in the
SODR register is full, respectively.
Asynchronous SCSI Receive –
Step 1. If the DMA FIFO size is set to 112 bytes (bit 5 of the Chip Test
Five (CTEST5) register cleared), look at the DMA FIFO
(DFIFO) and DMA Byte Counter (DBC) registers and calculate
if there are bytes left in the DMA FIFO. To make this calculation,
subtract the seven least significant bits of the DBC register from
the 7-bit value of the DFIFO register. AND the result with 0x7F
for a byte count between zero and 88.
If the DMA FIFO size is set to 944 bytes (bit 5 of the Chip Test
Five (CTEST5) register is set), subtract the 10 least significant
bits of the DMA Byte Counter (DBC) register from the 10-bit
value of the DMA FIFO Byte Offset Counter, which consists of
bits [1:0] in the CTEST5 register and bits [7:0] of the DMA FIFO
register. AND the result with 0x3FF for a byte count between
zero and 944.
Step 2. Read bit 7 in the SCSI Status Zero (SSTAT0) and SCSI Status
Two (SSTAT2) registers to determine if any bytes are left in the
SCSI Input Data Latch (SIDL) register. If bit 7 is set in the
SSTAT0 or SSTAT2 register, then the least significant byte or
the most significant byte is full, respectively.
Step 3. If any wide transfers have been performed using the Chained
Move instruction, read the Wide SCSI Receive bit (SCSI Status
Two (SSTAT2), bit 0) to determine whether a byte is left in the
SCSI Wide Residue (SWIDE) register.
Synchronous SCSI Receive –
Step 1. If the DMA FIFO size is set to 112 bytes, subtract the seven
least significant bits of the DMA Byte Counter (DBC) register
from the 7-bit value of the DMA FIFO (DFIFO) register. AND
the result with 0x7F for a byte count between zero and 112.
If the DMA FIFO size is set to 944 bytes (bit 5 of the Chip Test
Five (CTEST5) register is set), subtract the 10 least significant
bits of the DBC register from the 10-bit value of the DMA FIFO
Byte Offset Counter, which consists of bits [1:0] in the Chip Test
Five (CTEST5) register and bits [7:0] of the DMA FIFO register.

SCSI Functional Description

2-31

AND the result with 0x3FF for a byte count between zero and
944.
Step 2. Read the SCSI Status One (SSTAT1) register and examine bits
[7:4], the binary representation of the number of valid bytes in
the SCSI FIFO, to determine if any bytes are left in the SCSI
FIFO.
Step 3. If any wide transfers have been performed using the Chained
Move instruction, read the Wide SCSI Receive bit (SCSI
Control Two (SCNTL2), bit 0) to determine whether a byte is left
in the SCSI Wide Residue (SWIDE) register.

2.2.13 SCSI Bus Interface
The LSI53C875A performs SE transfers. TolerANT technology provides
signal filtering at the inputs of SREQ/ and SACK/ to increase immunity
to signal reflections.
2.2.13.1 SCSI Termination
The terminator networks provide the biasing needed to pull signals to an
inactive voltage level. They also match the impedance seen at the end
of the cable with the characteristic impedance of the cable. Terminators
must be installed at the extreme ends of the SCSI chain and only at the
ends. No system should ever have more or less than two terminators
installed and active. SCSI host adapters should provide a means of
accommodating terminators. The terminators should be socketed, so that
if not needed they may be removed, or there should be a means of
disabling them with software.
SE cables can use a 220 Ω pull-up to the terminator power supply
(Term Power) line and a 330 Ω pull-down to ground. Due to the high
performance nature of the LSI53C875A, regulated or active termination
is recommended. Figure 2.5 shows a Unitrode active terminator. For
additional information, refer to the SCSI-2 Specification. TolerANT
technology active negation can be used with either termination network.

2-32

Note:

If the LSI53C875A is used with an 8-bit SCSI bus, all
16 data lines must still be terminated or pulled HIGH.

Note:

Active termination is required for Ultra SCSI synchronous
transfers.

Functional Description

Figure 2.5

Regulated Termination for Ultra SCSI
UC5601QP
(UC5610 for Ultra SCSI)

2.85 V

2
C1

REG_OUT

DISCONNECT

TERML1
TERML2
TERML3
TERML4
TERML5
TERML6
TERML7
TERML8
TERML9

TERML10
TERML11
TERML12
TERML13
TERML14
TERML15
TERML16
TERML17
TERML18

20
21
22
23
24
25
26
27
28

3
4
5
6
7
8
9
10
11

SD0 (J1.40)
SD1 (J1.41)
SD2 (J1.42)
SD3 (J1.43)
SD4 (J1.44)
SD5 (J1.45)
SD6 (J1.46)
SD7 (J1.47)
SDP0 (J1.48)

ATN (J1.55)
BSY (J1.57)
ACK (J1.58)
RST (J1.59)
MSG (J1.60)
SEL (J1.61)
C/D (J1.62)
REQ (J1.63)
I/O (J1.64)

UC5603DP
(UC5614 for Ultra SCSI)

14
C3

REG_OUT

DISCONNECT

TERML1
TERML2
TERML3
TERML4
TERML5
TERML6
TERML7
TERML8
TERML9

10
9
8
7
3
2
1
16
15

SD15 (J1.38)
SD14 (J1.37)
SD13 (J1.36)
SD12 (J1.35)
SD11 (J1.68)
SD10 (J1.67)
SD9 (J1.66)
SD8 (J1.65)
SDP1 (J1.39)

Note:
1. C1 - 10 µF SMT
2. C2 - 0.1 µF SMT
3. C3 - 2.2 µF SMT
4. J1 - 68-pin, high density “P” connector

2.2.14 Select/Reselect During Selection/Reselection
In multithreaded SCSI I/O environments, it is not uncommon to be
selected or reselected while trying to perform selection/reselection. This

SCSI Functional Description

2-33

situation may occur when a SCSI controller (operating in the initiator
mode) tries to select a target and is reselected by another. The Select
SCRIPTS instruction has an alternate address to which the SCRIPTS will
jump when this situation occurs. The analogous situation for target
devices is being selected while trying to perform a reselection.
Once a change in operating mode occurs, the initiator SCRIPTS should
start with a Set Initiator instruction or the target SCRIPTS should start
with a Set Target instruction. The Selection and Reselection Enable bits
(SCSI Chip ID (SCID) bits 5 and 6, respectively) should both be asserted
so that the LSI53C875A may respond as an initiator or as a target. If only
selection is enabled, the LSI53C875A cannot be reselected as an
initiator. There are also status and interrupt bits in the SCSI Interrupt
Status Zero (SIST0) and SCSI Interrupt Enable Zero (SIEN0) registers,
respectively, indicating that the LSI53C875A has been selected (bit 5)
and reselected (bit 4).

2.2.15 Synchronous Operation
The LSI53C875A can transfer synchronous SCSI data in both the
initiator and target modes. The SCSI Transfer (SXFER) register controls
both the synchronous offset and the transfer period. It may be loaded by
the CPU before SCRIPTS execution begins, from within SCRIPTS using
a Table Indirect I/O instruction, or with a Read-Modify-Write instruction.
The LSI53C875A can receive data from the SCSI bus at a synchronous
transfer period as short as 50 ns, regardless of the transfer period used
to send data. The LSI53C875A can receive data at one-fourth of the
divided SCLK frequency. Depending on the SCLK frequency, the
negotiated transfer period, and the synchronous clock divider, the
LSI53C875A can send synchronous data at intervals as short as 50 ns
for Ultra SCSI, 100 ns for fast SCSI and 200 ns for SCSI-1.
2.2.15.1 Determining the Data Transfer Rate
Synchronous data transfer rates are controlled by bits in two different
registers of the LSI53C875A. Following is a brief description of the bits.
Figure 2.6 illustrates the clock division factors used in each register, and
the role of the register bits in determining the transfer rate.

2-34

Functional Description

Figure 2.6

Determining the Synchronous Transfer Rate
SCF2

SCF1

SCF0

0
0
0
1
0
1
1
1

0
1
1
0
0
0
1
1

1
0
1
0
0
1
0
1

SCF
Divisor
1
1.5
2
3
3
4
6
8

TP2

Clock
Quadrupler

TP0

0
0
1
1
0
0
1
1

0
1
0
1
0
1
0
1

0
0
0
0
1
1
1
1
This point
must not
exceed
160 MHz

SCLK

TP1

Divide by 4

SCF
Divider

Synchronous
Divider

CCF
Divider

Asynchronous
SCSI Logic

QCLK

CCF2
0
0
0
1
0
1
1
1

CCF1
0
1
1
0
0
0
1
1

CCF0
1
0
1
0
0
1
0
1

Divisor
1
1.5
2
3
3
4
6
8

Example 1 (using 40 MHz clock)
SCLK = 40 MHz

XFERP
Divisor
4
5
6
7
8
9
10
11
Receive
Clock

Send Clock
(to SCSI Bus)
This point must
not exceed 20 MHz.

QCLK (MHz)
50.1–66.00
16.67–25.00
25.1–37.50
37.51–50.00
50.01–66.00
75.01–80.00
120
160
Example 2 (using 20 MHz clock)
SCLK = 20 MHz

QCLK (Quadrupled SCSI Clock) = 160 MHz
QCLK (Quadrupled SCSI Clock) = 80 MHz
SCF = 1 (/1), XFERP = 4 (/8), CCF = 7 (/8)
SCF = 1 (/1), XFERP = 0 (/4), CCF = 5 (/4)
Synchronous send rate = (QCLK/SCF)/XFERP =
Synchronous send rate = (QCLK/SCF)/XFERP =
(160/1) /81 = 20 Mbytes/s
(80/1) /4 = 20 Mbytes/s
Synchronous receive rate = (QCLK/SCF) /4 =
Synchronous receive rate = (QCLK/SCF) /4 =
(160/1) /42 = 40 Mbytes/s
(80/1) /4 = 20 Mbytes/s
Note:
• Synchronous send rate must not exceed 20 Mbytes/s because the
LSI53C875A is an Ultra SCSI device.
• Although maximum synchronous receive rate is 40 Mbytes/s the
maximum transfer rate is 20 Mbytes/s because the LSI53C875A is an
Ultra SCSI device.

SCSI Functional Description

2-35

2.2.15.2 SCSI Control Three (SCNTL3) Register, Bits [6:4] (SCF[2:0])
The SCF[2:0] bits select the factor by which the frequency of SCLK is
divided before being presented to the synchronous SCSI control logic.
The output from this divider controls the rate at which data can be
received; this rate must not exceed 160 MHz. The receive rate of
synchronous SCSI data is one-fourth of the SCF divider output. For
example, if SCLK is 80 MHz and the SCF value is set to divide by one,
then the maximum rate at which data can be received is 20 MHz
(80/(1*4) = 20).
2.2.15.3 SCSI Control Three (SCNTL3) Register, Bits [2:0] (CCF[2:0])
The CCF[2:0] bits select the factor by which the frequency of SCLK is
divided before being presented to the asynchronous SCSI core logic.
This divider must be set according to the input clock frequency in the
table.
2.2.15.4 SCSI Transfer (SXFER) Register, Bits [7:5] (TP[2:0])
The TP[2:0] divider bits determine the SCSI synchronous transfer period
when sending synchronous SCSI data in either the initiator or target
mode. This value further divides the output from the SCF divider.
2.2.15.5 Ultra SCSI Synchronous Data Transfers
Ultra SCSI is an extension of the current Fast SCSI-2 synchronous
transfer specifications. It allows synchronous transfer periods to be
negotiated down as low as 50 ns, which is half the 100 ns period allowed
under Fast SCSI-2. This allows a maximum transfer rate of 40 Mbytes/s
on a 16-bit SCSI bus. The LSI53C875A has a SCSI clock quadrupler that
must be enabled for the chip to perform Ultra SCSI transfers with a 20
or 40 MHz oscillator. In addition, the following bit values affect the chip’s
ability to support Ultra SCSI synchronous transfer rates:

•

2-36

Clock Conversion Factor bits, SCSI Control Three (SCNTL3) register
bits [2:0] and Synchronous Clock Conversion Factor bits, SCNTL3
register bits [6:4]. These fields support a value of 111 (binary),
allowing the 160 MHz SCLK frequency to be divided by 8 for the
asynchronous logic.

Functional Description

•

Ultra SCSI Enable bit, SCSI Control Three (SCNTL3) register bit 7.
Setting this bit enables Ultra SCSI synchronous transfers in systems
that use the internal SCSI clock quadrupler.

•

TolerANT Enable bit, SCSI Test Three (STEST3) register bit 7. Active
negation must be enabled for the LSI53C875A to perform Ultra SCSI
transfers.

2.2.16 Interrupt Handling
The SCRIPTS processors in the LSI53C875A perform most functions
independently of the host microprocessor. However, certain interrupt
situations must be handled by the external microprocessor. This section
explains all aspects of interrupts as they apply to the LSI53C875A.
2.2.16.1 Polling and Hardware Interrupts
The external microprocessor is informed of an interrupt condition by
polling or hardware interrupts. Polling means that the microprocessor
must continually loop and read a register until it detects a bit that is set
indicating an interrupt. This method is the fastest, but it wastes CPU time
that could be used for other system tasks. The preferred method of
detecting interrupts in most systems is hardware interrupts. In this case,
the LSI53C875A asserts the Interrupt Request (IRQ/) line that interrupts
the microprocessor, causing the microprocessor to execute an interrupt
service routine. A hybrid approach would use hardware interrupts for
long waits, and use polling for short waits.
2.2.16.2 Registers
The registers in the LSI53C875A that are used for detecting or defining
interrupts are Interrupt Status Zero (ISTAT0), Interrupt Status One
(ISTAT1), Mailbox Zero (MBOX0), Mailbox One (MBOX1), SCSI Interrupt
Status Zero (SIST0), SCSI Interrupt Status One (SIST1), DMA Status
(DSTAT), SCSI Interrupt Enable Zero (SIEN0), SCSI Interrupt Enable
One (SIEN1), DMA Control (DCNTL), and DMA Interrupt Enable (DIEN).
ISTAT – The ISTAT register includes the Interrupt Status Zero (ISTAT0),
Interrupt Status One (ISTAT1), Chip Test Zero (CTEST0), and Mailbox
One (MBOX1) registers. It is the only register that can be accessed as a
slave during the SCRIPTS operation. Therefore, it is the register that is

SCSI Functional Description

2-37

polled when polled interrupts are used. It is also the first register that
should be read after the IRQ/ pin is asserted in association with a
hardware interrupt. The INTF (Interrupt-on-the-Fly) bit should be the first
interrupt serviced. It must be written to one to be cleared. This interrupt
must be cleared before servicing any other interrupts.
See Register 0x14, Interrupt Status Zero (ISTAT0) register, bit 5 Signal
process in Chapter 4, “Registers,” for additional information.
The host (C Code) or the SCRIPTS code could potentially try to access
the mailbox bits at the same time.
If the SIP bit in the Interrupt Status Zero (ISTAT0) register is set, then a
SCSI-type interrupt has occurred and the SCSI Interrupt Status Zero
(SIST0) and SCSI Interrupt Status One (SIST1) registers should be read.
If the DIP bit in the Interrupt Status Zero (ISTAT0) register is set, then a
DMA-type interrupt has occurred and the DMA Status (DSTAT) register
should be read.
SCSI-type and DMA-type interrupts may occur simultaneously, so in
some cases both SIP and DIP may be set.
SIST0 and SIST1 – The SCSI Interrupt Status Zero (SIST0) and SCSI
Interrupt Status One (SIST1) registers contain SCSI-type interrupt bits.
Reading these registers determines which condition or conditions caused
the SCSI-type interrupt, and clears that SCSI interrupt condition.
If the LSI53C875A is receiving data from the SCSI bus and a fatal
interrupt condition occurs, the chip attempts to send the contents of the
DMA FIFO to memory before generating the interrupt.
If the LSI53C875A is sending data to the SCSI bus and a fatal SCSI
interrupt condition occurs, data could be left in the DMA FIFO. Because
of this the DMA FIFO Empty (DFE) bit in DMA Status (DSTAT) should be
checked.
If this bit is cleared, set the CLF (Clear DMA FIFO) and CSF (Clear SCSI
FIFO) bits before continuing. The CLF bit is bit 2 in Chip Test Three
(CTEST3). The CSF bit is bit 1 in SCSI Test Three (STEST3).
DSTAT – The DMA Status (DSTAT) register contains the DMA-type
interrupt bits. Reading this register determines which condition or

2-38

Functional Description

conditions caused the DMA-type interrupt, and clears that DMA interrupt
condition. Bit 7 in DSTAT, DFE, is purely a status bit; it will not generate
an interrupt under any circumstances and will not be cleared when read.
DMA interrupts flush neither the DMA nor SCSI FIFOs before generating
the interrupt, so the DFE bit in the DMA Status (DSTAT) register should
be checked after any DMA interrupt.
If the DFE bit is cleared, then the FIFOs must be cleared by setting the
CLF (Clear DMA FIFO) and CSF (Clear SCSI FIFO) bits, or flushed by
setting the FLF (Flush DMA FIFO) bit.
SIEN0 and SIEN1 – The SCSI Interrupt Enable Zero (SIEN0) and SCSI
Interrupt Enable One (SIEN1) registers are the interrupt enable registers
for the SCSI interrupts in SCSI Interrupt Status Zero (SIST0) and SCSI
Interrupt Status One (SIST1).
DIEN – The DMA Interrupt Enable (DIEN) register is the interrupt enable
register for DMA interrupts in DMA Status (DSTAT).
DCNTL – When bit 1 in the DMA Control (DCNTL) register is set, the
IRQ/ pin is not asserted when an interrupt condition occurs. The interrupt
is not lost or ignored, but is merely masked at the pin. Clearing this bit
when an interrupt is pending immediately causes the IRQ/ pin to assert.
As with any register other than ISTAT, this register cannot be accessed
except by a SCRIPTS instruction during SCRIPTS execution.
2.2.16.3 Fatal vs. Nonfatal Interrupts
A fatal interrupt, as the name implies, always causes the SCRIPTS to
stop running. All nonfatal interrupts become fatal when they are enabled
by setting the appropriate interrupt enable bit. Interrupt masking is
discussed in Section 2.2.16.4, “Masking.” All DMA interrupts (indicated
by the DIP bit in ISTAT and one or more bits in DMA Status (DSTAT)
being set) are fatal.
Some SCSI interrupts (indicated by the SIP bit in the Interrupt Status
Zero (ISTAT0) and one or more bits in SCSI Interrupt Status Zero
(SIST0) or SCSI Interrupt Status One (SIST1) being set) are nonfatal.
When the LSI53C875A is operating in the Initiator mode, only the
Function Complete (CMP), Selected (SEL), Reselected (RSL), General

SCSI Functional Description

2-39

Purpose Timer Expired (GEN), and Handshake-to-Handshake Timer
Expired (HTH) interrupts are nonfatal.
When operating in the Target mode, CMP, SEL, RSL, Target mode:
SATN/ active (M/A), GEN, and HTH are nonfatal. Refer to the description
for the Disable Halt on a Parity Error or SATN/ active (Target Mode Only)
(DHP) bit in the SCSI Control One (SCNTL1) register to configure the
chip’s behavior when the SATN/ interrupt is enabled during Target mode
operation. The Interrupt-on-the-Fly interrupt is also nonfatal, since
SCRIPTS can continue when it occurs.
The reason for nonfatal interrupts is to prevent the SCRIPTS from
stopping when an interrupt occurs that does not require service from the
CPU. This prevents an interrupt when arbitration is complete (CMP set),
when the LSI53C875A is selected or reselected (SEL or RSL set), when
the initiator asserts ATN (target mode: SATN/ active), or when the
General Purpose or Handshake-to-Handshake timers expire. These
interrupts are not needed for events that occur during high-level
SCRIPTS operation.
2.2.16.4 Masking
Masking an interrupt means disabling or ignoring that interrupt. Interrupts
can be masked by clearing bits in the SCSI Interrupt Enable Zero
(SIEN0) and SCSI Interrupt Enable One (SIEN1) (for SCSI interrupts)
registers or DMA Interrupt Enable (DIEN) (for DMA interrupts) register.
How the chip responds to masked interrupts depends on: whether polling
or hardware interrupts are being used; whether the interrupt is fatal or
nonfatal; and whether the chip is operating in the Initiator or Target mode.
If a nonfatal interrupt is masked and that condition occurs, the SCRIPTS
do not stop, the appropriate bit in the SCSI Interrupt Status Zero (SIST0)
or SCSI Interrupt Status One (SIST1) is still set, the SIP bit in the
Interrupt Status Zero (ISTAT0) is not set, and the IRQ/ pin is not
asserted.
If a fatal interrupt is masked and that condition occurs, then the SCRIPTS
still stop, the appropriate bit in the DMA Status (DSTAT), SCSI Interrupt
Status Zero (SIST0), or SCSI Interrupt Status One (SIST1) register is
set, and the SIP or DIP bit in the Interrupt Status Zero (ISTAT0) register
is set, but the IRQ/ pin is not asserted.

2-40

Functional Description

Interrupts can be disabled by setting SYNC_IRQD bit 0 in the Interrupt
Status One (ISTAT1) register. If an interrupt is already asserted and
SYNC_IRQD is then set, the interrupt will remain asserted until serviced.
At this point, the IRQ/ pin is blocked for future interrupts until this bit is
cleared. When the LSI53C875A is initialized, enable all fatal interrupts if
you are using hardware interrupts. If a fatal interrupt is disabled and that
interrupt condition occurs, the SCRIPTS halt and the system never
knows it unless it times out and checks the ISTAT register after a certain
period of inactivity.
If you are polling the ISTAT instead of using hardware interrupts, then
masking a fatal interrupt makes no difference since the SIP and DIP bits
in the Interrupt Status Zero (ISTAT0) inform the system of interrupts, not
the IRQ/ pin.
Masking an interrupt after IRQ/ is asserted does not cause deassertion
of IRQ/.
2.2.16.5 Stacked Interrupts
The LSI53C875A will stack interrupts if they occur one after the other. If
the SIP or DIP bits in the ISTAT register are set (first level), then there is
already at least one pending interrupt, and any future interrupts are
stacked in extra registers behind the SCSI Interrupt Status Zero (SIST0),
SCSI Interrupt Status One (SIST1), and DMA Status (DSTAT) registers
(second level). When two interrupts have occurred and the two levels of
the stack are full, any further interrupts set additional bits in the extra
registers behind SCSI Interrupt Status Zero (SIST0), SCSI Interrupt
Status One (SIST1), and DMA Status (DSTAT). When the first level of
interrupts are cleared, all the interrupts that came in afterward move into
SIST0, SIST1, and DSTAT. After the first interrupt is cleared by reading
the appropriate register, the IRQ/ pin is deasserted for a minimum of
three CLKs; the stacked interrupts move into SIST0, SIST1, or DSTAT;
and the IRQ/ pin is asserted once again.
Since a masked nonfatal interrupt does not set the SIP or DIP bits,
interrupt stacking does not occur. A masked, nonfatal interrupt still posts
the interrupt in SIST0, but does not assert the IRQ/ pin. Since no
interrupt is generated, future interrupts move into SCSI Interrupt Status
Zero (SIST0) or SCSI Interrupt Status One (SIST1) instead of being
stacked behind another interrupt. When another condition occurs that

SCSI Functional Description

2-41

generates an interrupt, the bit corresponding to the earlier masked
nonfatal interrupt is still set.
A related situation to interrupt stacking is when two interrupts occur
simultaneously. Since stacking does not occur until the SIP or DIP bits
are set, there is a small timing window in which multiple interrupts can
occur but are not stacked. These could be multiple SCSI interrupts (SIP
set), multiple DMA interrupts (DIP set), or multiple SCSI and multiple
DMA interrupts (both SIP and DIP set).
As previously mentioned, DMA interrupts do not attempt to flush the
FIFOs before generating the interrupt. It is important to set either the
Clear DMA FIFO (CLF) and Clear SCSI FIFO (CSF) bits if a DMA
interrupt occurs and the DMA FIFO Empty (DFE) bit is not set. This is
because any future SCSI interrupts are not posted until the DMA FIFO
is cleared of data. These ‘locked out’ SCSI interrupts are posted as soon
as the DMA FIFO is empty.
2.2.16.6 Halting in an Orderly Fashion
When an interrupt occurs, the LSI53C875A attempts to halt in an orderly
fashion.

2-42

•

If the interrupt occurs in the middle of an instruction fetch, the fetch
is completed, except in the case of a Bus Fault. Execution does not
begin, but the DMA SCRIPTS Pointer (DSP) points to the next
instruction since it is updated when the current instruction is fetched.

•

If the DMA direction is a write to memory and a SCSI interrupt
occurs, the LSI53C875A attempts to flush the DMA FIFO to memory
before halting. Under any other circumstances only the current cycle
is completed before halting, so the DFE bit in DMA Status (DSTAT)
register should be checked to see if any data remains in the DMA
FIFO.

•

SCSI SREQ/SACK handshakes that have begun are completed
before halting.

•

The LSI53C875A attempts to clean up any outstanding synchronous
offset before halting.

•

In the case of Transfer Control Instructions, once instruction
execution begins it continues to completion before halting.

Functional Description

•

If the instruction is a JUMP/CALL WHEN/IF , the DMA
SCRIPTS Pointer (DSP) is updated to the transfer address before
halting.

•

All other instructions may halt before completion.

2.2.16.7 Sample Interrupt Service Routine
The following is a sample of an interrupt service routine for the
LSI53C875A. It can be repeated during polling or should be called when
the IRQ/ pin is asserted during hardware interrupts.
1. Read Interrupt Status Zero (ISTAT0).
2. If the INTF bit is set, it must be written to a one to clear this status.
3. If only the SIP bit is set, read SCSI Interrupt Status Zero (SIST0) and
SCSI Interrupt Status One (SIST1) to clear the SCSI interrupt
condition and get the SCSI interrupt status. The bits in the SIST0
and SIST1 tell which SCSI interrupts occurred and determine what
action is required to service the interrupts.
4. If only the DIP bit is set, read DMA Status (DSTAT) to clear the
interrupt condition and get the DMA interrupt status. The bits in
DSTAT tell which DMA interrupts occurred and determine what action
is required to service the interrupts.
5. If both the SIP and DIP bits are set, read SCSI Interrupt Status Zero
(SIST0), SCSI Interrupt Status One (SIST1), and DMA Status
(DSTAT) to clear the SCSI and DMA interrupt condition and get the
interrupt status. If using 8-bit reads of the SIST0, SIST1, and DSTAT
registers to clear interrupts, insert a 12 CLK delay between the
consecutive reads to ensure that the interrupts clear properly. Both
the SCSI and DMA interrupt conditions should be handled before
leaving the interrupt service routine. It is recommended that the DMA
interrupt is serviced before the SCSI interrupt, because a serious
DMA interrupt condition could influence how the SCSI interrupt is
acted upon.
6. When using polled interrupts, go back to Step 1 before leaving the
interrupt service routine, in case any stacked interrupts moved in
when the first interrupt was cleared. When using hardware interrupts,
the IRQ/ pin is asserted again if there are any stacked interrupts.
This should cause the system to re-enter the interrupt service
routine.

SCSI Functional Description

2-43

2.2.17 Chained Block Moves
Since the LSI53C875A has the capability to transfer 16-bit wide SCSI
data, a unique situation occurs when dealing with odd bytes. The
Chained Move (CHMOV) SCRIPTS instruction along with the Wide SCSI
Send (WSS) and Wide SCSI Receive (WSR) bits in the SCSI Control
Two (SCNTL2) register are used to facilitate these situations. The
Chained Block Move instruction is illustrated in Figure 2.7.

2-44

Functional Description

Figure 2.7

Block Move and Chained Block Move Instructions

Host Memory

SCSI Bus

0x03

0x02

0x01

0x00

0x04

0x03

0x07

0x06

0x05

0x04

0x06

0x05

0x0B

0x0A

0x09

0x08

0x0F

0x0E

0x0D

0x0C

0x13

0x12

0x11

0x10

0x09

0x07

0x0B

0x0A

0x0D

0x0C

32 Bits

16 Bits

2.2.17.1 Wide SCSI Send Bit
The WSS bit is set whenever the SCSI controller is sending data
(Data-Out for initiator or Data-In for target) and the controller detects a
partial transfer at the end of a chained Block Move SCRIPTS instruction
(this flag is not set if a normal Block Move instruction is used). Under this
condition, the SCSI controller does not send the low-order byte of the last
partial memory transfer across the SCSI bus. Instead, the low-order byte
is temporarily stored in the lower byte of the SCSI Output Data Latch
(SODL) register and the WSS flag is set. The hardware uses the WSS
flag to determine what behavior must occur at the start of the next data
send transfer. When the WSS flag is set at the start of the next transfer,
the first byte (the high-order byte) of the next data send transfer is
“married” with the stored low-order byte in the SODL register; and the

SCSI Functional Description

2-45

two bytes are sent out across the bus, regardless of the type of Block
Move instruction (normal or chained). The flag is automatically cleared
when the “married” word is sent. The flag is alternately cleared through
SCRIPTS or by the microprocessor. Also, the microprocessor or
SCRIPTS can use this bit for error detection and recovery purposes.
2.2.17.2 Wide SCSI Receive Bit
The WSR bit is set whenever the SCSI controller is receiving data
(Data-In for initiator or Data-Out for target) and the controller detects a
partial transfer at the end of a block move or chained block move
SCRIPTS instruction. When WSR is set, the high-order byte of the last
SCSI bus transfer is not transferred to memory. Instead, the byte is
temporarily stored in the SCSI Wide Residue (SWIDE) register. The
hardware uses the WSR bit to determine what behavior must occur at
the start of the next data receive transfer. The bit is automatically cleared
at the start of the next data receive transfer. The bit can alternatively be
cleared by the microprocessor or through SCRIPTS. Also, the
microprocessor or SCRIPTS can use this bit for error detection and
recovery purposes.
2.2.17.3 SWIDE Register
This register stores data for partial byte data transfers. For receive data,
the SCSI Wide Residue (SWIDE) register holds the high-order byte of a
partial SCSI transfer which has not yet been transferred to memory. This
stored data may be a residue byte (and therefore ignored) or it may be
valid data that is transferred to memory at the beginning of the next Block
Move instruction.
2.2.17.4 SODL Register
For send data, the low-order byte of the SCSI Output Data Latch (SODL)
register holds the low-order byte of a partial memory transfer which has
not yet been transferred across the SCSI bus. This stored data is usually
“married” with the first byte of the next data send transfer, and both bytes
are sent across the SCSI bus at the start of the next data send block
move command.

2-46

Functional Description

2.2.17.5 Chained Block Move SCRIPTS Instruction
A chained Block Move SCRIPTS instruction is primarily used to transfer
consecutive data send or data receive blocks. Using the chained Block
Move instruction facilitates partial receive transfers and allows correct
partial send behavior without additional opcode overhead. Behavior of
the chained Block Move instruction varies slightly for sending and
receiving data.
For receive data (Data-In for initiator or Data-Out for target), a chained
Block Move instruction indicates that if a partial transfer occurred at the
end of the instruction, the WSR flag is set. The high-order byte of the
last SCSI transfer is stored in the SCSI Wide Residue (SWIDE) register
rather than transferred to memory. The contents of the SWIDE register
should be the first byte transferred to memory at the start of the chained
Block Move data stream. Since the byte count always represents data
transfers to/from memory (as opposed to the SCSI bus), the byte
transferred out of the SCSI Wide Residue (SWIDE) register is one of the
bytes in the byte count. If the WSR bit is cleared when a receive data
chained Block Move instruction is executed, the data transfer occurs
similar to that of the regular Block Move instruction. Whether the WSR
bit is set or cleared, when a normal block move instruction is executed,
the contents of the SCSI Wide Residue (SWIDE) register are ignored
and the transfer takes place normally. For “N” consecutive wide data
receive Block Move instructions, the 2nd through the Nth Block Move
instructions should be chained block moves.
For send data (Data-Out for initiator or Data-In for target), a chained
Block Move instruction indicates that if a partial transfer terminates the
chained block move instruction, the last low-order byte (the partial
memory transfer) should be stored in the lower byte of the SCSI Output
Data Latch (SODL) register and not sent across the SCSI bus. Without
the chained Block Move instruction, the last low-order byte would be sent
across the SCSI bus. The starting byte count represents data bytes
transferred from memory but not to the SCSI bus when a partial transfer
exists. For example, if the instruction is an Initiator chained Block Move
Data Out of five bytes (and WSS is not previously set), five bytes are
transferred out of memory to the SCSI controller, four bytes are
transferred from the SCSI controller across the SCSI bus, and one byte
is temporarily stored in the lower byte of the SCSI Output Data Latch
(SODL) register waiting to be married with the first byte of the next Block
Move instruction. Regardless of whether a chained Block Move or normal
Block Move instruction is used, if the WSS bit is set at the start of a data

SCSI Functional Description

2-47

send command, the first byte of the data send command is assumed to
be the high-order byte and is “married” with the low-order byte stored in
the lower byte of the SCSI Output Data Latch (SODL) register before the
two bytes are sent across the SCSI bus. For “N” consecutive wide data
send Block Move commands, the first through the (Nth – 1) Block Move
instructions should be Chained Block Moves.
CHMOV 5, 3 when Data_Out
Moves five bytes from address 0x03 in the host memory to the SCSI bus.
Bytes 0x03, 0x04, 0x05, and 0x06 are moved and byte 0x07 remains in
the low-order byte of the SCSI Output Data Latch (SODL) register and
is married with the first byte of the following MOVE instruction.
MOVE 5, 9 when Data_Out
Moves five bytes from address 0x09 in the host memory to the SCSI bus.

2.3 Parallel ROM Interface
The LSI53C875A supports up to one megabyte of external memory in
binary increments from 16 Kbytes, to allow the use of expansion ROM
for add-in PCI cards. This interface is designed for low speed operations
such as downloading instruction code from ROM; it is not intended for
dynamic activities such as executing instructions.
System requirements include the LSI53C875A, two or three external
8-bit address holding registers (HCT273 or HCT374), and the
appropriate memory device. The 4.7 kΩ pull-up resistors on the MAD bus
require HC or HCT external components to be used. If in-system Flash
ROM updates are required, a 7406 (high voltage open collector inverter),
a MTD4P05, and several passive components are also needed. The
memory size and speed is determined by pull-up resistors on the
8-bit bidirectional memory bus at power-up. The LSI53C875A senses this
bus shortly after the release of the Reset signal and configures the
Expansion ROM Base Address register and the memory cycle state
machines for the appropriate conditions.
The external memory interface works with a variety of ROM sizes and
speeds. An example set of interface drawings is in Appendix B, “External
Memory Interface Diagram Examples.”

2-48

Functional Description

The LSI53C875A supports a variety of sizes and speeds of expansion
ROM, using pull-down resistors on the MAD[3:0] pins. The encoding of
pins MAD[3:1] allows the user to define how much external memory is
available to the LSI53C875A. Table 2.6 shows the memory space
associated with the possible values of MAD[3:1]. The MAD[3:1] pins are
fully described in Chapter 3, “Signal Descriptions.”
Table 2.6

Parallel ROM Support

MAD[3:1]

Available Memory Space

000

16 Kbytes

001

32 Kbytes

010

64 Kbytes

011

128 Kbytes

100

256 Kbytes

101

512 Kbytes

110

1024 Kbytes

111

no external memory present

To use one of the configurations mentioned above in a host adapter
board design, put 4.7 kΩ pull-up resistors on the MAD pins
corresponding to the available memory space. For example, to connect
to a 64 Kbyte external ROM, use a pull-up on MAD2. If the external
memory interface is not used, MAD[3:1] should be pulled HIGH.
Note:

There are internal pull-downs on all of the MAD bus
signals.

The LSI53C875A allows the system to determine the size of the available
external memory using the Expansion ROM Base Address register in the
PCI configuration space. For more information on how this works, refer
to the PCI specification or the Expansion ROM Base Address register
description in Chapter 4, “Registers.”
MAD0 is the slow ROM pin. When pulled up, it enables two extra clock
cycles of data access time to allow use of slower memory devices. The
external memory interface also supports updates to flash memory.

Parallel ROM Interface

2-49

2.4 Serial EEPROM Interface
The LSI53C875A implements an interface that allows attachment of a
serial EEPROM device to the GPIO0 and GPIO1 pins. There are two
modes of operation relating to the serial EEPROM and the Subsystem
ID and Subsystem Vendor ID registers. These modes are programmable
through the MAD7 pin which is sampled at power-up.

2.4.1 Default Download Mode
In this mode, MAD7 is pulled down internally, GPIO0 is the serial data
signal (SDA) and GPIO1 is the serial clock signal (SCL). Certain data in
the serial EEPROM is automatically loaded into chip registers at
power-up.
The format of the serial EEPROM data is defined in Table 2.7. If the
download is enabled and an EEPROM is not present, or the checksum
fails, the Subsystem ID and Subsystem Vendor ID registers read back all
zeros. At power-up, only five bytes are loaded into the chip from locations
0xFB through 0xFF.
The Subsystem ID and Subsystem Vendor ID registers are read only, in
accordance with the PCI specification, with a default value of all zeros if
the download fails.

2-50

Functional Description

Table 2.7

Mode A Serial EEPROM Data Format

Byte

Name

0xFB

SVID(0) Subsystem Vendor ID, LSB. This byte is loaded into the least significant
byte of the Subsystem Vendor ID register in the appropriate PCI
configuration space at chip power-up.

0xFC

SVID(1) Subsystem Vendor ID, MSB. This byte is loaded into the most significant
byte of the Subsystem Vendor ID register in the appropriate PCI
configuration space at chip power-up.

0xFD

SID(0)

Subsystem ID, LSB. This byte is loaded into the least significant byte of
the Subsystem ID register in the appropriate PCI configuration space at
chip power-up.

0xFE

SID(1)

Subsystem ID, MSB. This byte is loaded into the most significant byte of
the Subsystem ID register in the appropriate PCI configuration space at
chip power-up.

0xFF

CKSUM Checksum. This 8-bit checksum is formed by adding, bytewise, each byte
contained in locations 0x00–0x03 to the seed value 0x55, and then taking
the 2s complement of the result.

0x100–0xEOM UD

Description

User Data.

2.4.2 No Download Mode
When MAD7 is pulled up through an external resistor, the automatic
download is disabled and no data is automatically loaded into chip
registers at power-up. The Subsystem ID and Subsystem Vendor ID
registers are read only, per the PCI specification, with a default value of
0x1000 and 0x1000 respectively.

2.5 Power Management
The LSI53C875A complies with the PCI Bus Power Management
Interface Specification, Revision 1.1. The PCI Function Power States D0,
D1, D2, and D3 are defined in that specification.
D0 is the maximum powered state, and D3 is the minimum powered
state. Power state D3 is further categorized as D3hot or D3cold. A
function that is powered off is said to be in the D3cold power state.

Power Management

2-51

The LSI53C875A power states shown in Table 2.8 are independently
controlled through two power state bits that are located in the PCI Power
Management Control/Status (PMCSR) register 0x44.
Table 2.8

Power States

Configuration Register 0x44
Bits [1:0]

Power State

Maximum Power

Disables SCSI Clock

Coma Mode

Minimum Power

Function

Although the PCI Bus Power Management Interface Specification does
not allow power state transitions D2 to D1, D3 to D2, or D3 to D1, the
LSI53C875A hardware places no restriction on transitions between
power states.
As the device transitions from one power level to a lower one, the
attributes that occur from the higher power state level are carried over
into the lower power state level. For example, D1 disables the SCSI CLK.
Therefore, D2 will include this attribute as well as the attributes defined
in the Power State D2 section. The PCI Function Power States D0, D1,
D2, and D3 are described below. Power state actions are separate for
each function.

2.5.1 Power State D0
Power state D0 is the maximum power state and is the power-up default
state. The LSI53C875A is fully functional in this state.

2.5.2 Power State D1
Power state D1 is a lower power state than D0. In this state, the
LSI53C875A core is placed in the snooze mode and the SCSI CLK is
disabled. In the snooze mode, a SCSI reset does not generate an IRQ/
signal. However, the SCSI CLK is still disabled.

2-52

Functional Description

2.5.3 Power State D2
Power state D2 is a lower power state than D1. In this state the
LSI53C875A core is placed in the coma mode. The following PCI
Configuration Space command register enable bits are suppressed:

•

I/O Space Enable

•

Memory Space Enable

•

Bus Mastering Enable

•

SERR/Enable

•

Enable Parity Error Response

Thus, the memory and I/O spaces cannot be accessed, and the
LSI53C875A cannot be a PCI bus master. Furthermore, all interrupts are
disabled when in power state D2. If changed from power state D2 to
power state D0, the previous values of the PCI command register are
restored. Also, any pending interrupts before the function entered power
state D2 are asserted.

2.5.4 Power State D3
Power state D3 is the minimum power state, which includes settings
called D3hot and D3cold. D3hot allows the device to transition to D0
using software. The LSI53C875A is considered to be in power state
D3cold when power is removed from the device. D3cold can transition to
D0 by applying VCC and resetting the device. Furthermore, the device's
soft reset is continually asserted while in power state D3, which clears
all pending interrupts and 3-states the SCSI bus. In addition, the device's
PCI command register is cleared and the Clock Quadrupler is disabled,
which results in additional power savings.

Power Management

2-53

2-54

Functional Description

Chapter 3
Signal Descriptions

This chapter presents the LSI53C875A pin configuration and signal
definitions using tables and illustrations. This chapter contains the
following sections:

•

Section 3.1, “LSI53C875A Functional Signal Grouping”

•

Section 3.2, “Signal Descriptions”

•

Section 3.3, “PCI Bus Interface Signals”

•

Section 3.4, “SCSI Bus Interface Signals”

•

Section 3.5, “GPIO Signals”

•

Section 3.6, “ROM Flash and Memory Interface Signals”

•

Section 3.7, “Test Interface Signals”

•

Section 3.8, “Power and Ground Signals”

•

Section 3.9, “MAD Bus Programming”

A slash (/) at the end of a signal name indicates that the active state
occurs when the signal is at a LOW voltage. When the slash is absent,
the signal is active at a HIGH voltage.

LSI53C875A PCI to Ultra SCSI Controller

3-1

3.1 LSI53C875A Functional Signal Grouping
Figure 3.1 presents the LSI53C875A signals by functional group.
Figure 3.1

LSI53C875A Functional Signal Grouping
LSI53C875A

System

CLK
RST/
SCLK
AD[31:0]
C_BE[3:0]/
PAR

Interface
Control

FRAME/
TRDY/
IRDY/
STOP/
DEVSEL/
IDSEL

Arbitration

REQ/
GNT/

Error
Reporting

PERR/
SERR/

Interrupt

IRQ/

SCSI
Function
GPIO

GPIO0_FETCH/
GPIO1_MASTER/
GPIO2
GPIO3
GPIO4

ROM Flash
& Memory
Interface

3-2

MWE/
MCE/
MOE/
MAC/_TESTOUT
MAS0/
MAS1/
MAD[7:0]

Signal Descriptions

SD[15:0]
SDP[1:0]

SCD
SIO
SMSG
SREQ
SACK
SBSY
SATN
SRST
SSEL

TEST_RST/
TEST_HSC/
MAC/_TESTOUT
TCK
TMS
TDI
TDO
TRST/

SCSI

Test
Interface

SCSI Bus Interface

PCI Bus Interface

Address
and
Data

3.2 Signal Descriptions
The Signal Descriptions are divided into PCI Bus Interface Signals, SCSI
Bus Interface Signals, GPIO Signals, ROM Flash and Memory Interface
Signals, Test Interface Signals, and Power and Ground Signals.
The PCI Bus Interface Signals are subdivided into System Signals,
Address and Data Signals, Interface Control Signals, Arbitration Signals,
Error Reporting Signals, and Interrupt Signal.
The SCSI Bus Interface Signals are subdivided into SCSI Bus Interface
Signals, SCSI Signals, and SCSI Control Signals.
Signals are assigned a type. There are five signal types:
I

Input, a standard input only signal.

Output, a standard output driver (typically a Totem Pole Output).

I/O

Input and output (bidirectional).

T/S

3-state, a bidirectional, 3-state input/output signal.

S/T/S

Sustained 3-state, an active LOW 3-state signal owned and driven by
one and only one agent at a time.

3.2.1 Internal Pull-ups on LSI53C875A Signals
Several signals in the LSI53C875A have internal pull-up resistors.
Table 3.1 describes the conditions that enable these pull-ups.
Table 3.1

LSI53C875A Internal Pull-ups

Signal Name

Pull-up Current Conditions for Pull-up

IRQ/

25 µA

Pull-up enabled when the IRQ mode bit (bit 3 of DCNTL
(0x3B)) is cleared.

GPIO[1:0]

25 µA

Pull-up enabled when bits [1:0] of General Purpose Pin
Control Zero (GPCNTL0) are not set.

TEST_HSC/

25 µA

Pull-up enabled all the time.

TEST_RST/

25 µA

Pull-up enabled all the time.

TRST, TCK, TMS, TDI

25 µA

Pull-up enabled all the time.

Signal Descriptions

3-3

3.3 PCI Bus Interface Signals
The PCI Bus Interface Signals section contains tables describing the
signals for the following signal groups: System Signals, Address and
Data Signals, Interface Control Signals, Arbitration Signals, Error
Reporting Signals, and Interrupt Signal.

3.3.1 System Signals
Table 3.2 describes the System signals.
Table 3.2

System Signals

Name

PQFP

BGA

CLK

145

N/A

Clock provides timing for all transactions on the PCI bus
and is an input to every PCI device. All other PCI signals
are sampled on the rising edge of CLK, and other timing
parameters are defined with respect to this edge. Clock
can optionally serve as the SCSI core clock, but this may
effect fast SCSI-2 (or faster) transfer rates.

RST/

144

N/A

Reset forces the PCI sequencer of each device to a
known state. All T/S and S/T/S signals are forced to a high
impedance state, and all internal logic is reset. The RST/
input is synchronized internally to the rising edge of CLK.
The CLK input must be active while RST/ is active to
properly reset the device.

3-4

Type Strength Description

Signal Descriptions

3.3.2 Address and Data Signals
Table 3.3 describes Address and Data signals.
Table 3.3

Address and Data Signals

Name

PQFP

BGA

Type Strength Description

AD[31:0]

150, 151,
153, 154,
156, 157,
159, 160, 3,
5, 6, 7, 9,
11–13, 28–
30, 32, 34–
36, 38, 40,
41, 43, 44,
46, 47, 49,
50

B5, C5, A4,
B4, A3, C4,
D4, A2, C2,
E5, C1, D3,
E4-E1, H5,
J1, J2, H6,
K2, J4, L1,
L2, M1, N1,
M3, L3, N3,
L4, K5, N4

T/S

8 mA
PCI

Physical Dword Address and Data are
multiplexed on the same PCI pins. A bus
transaction consists of an address phase
followed by one or more data phases.
During the first clock of a transaction,
AD[31:0] contain a 32-bit physical byte
address. If the command is a DAC,
implying a 64-bit address, a second
address phase is required. During the
first phase, AD[31:0] will contain the
lower 32 bits of the address followed by
a second phase with AD[31:0] containing
the upper 32 bits of the address. During
subsequent clocks, AD[31:0] contain
data. PCI supports both read and write
bursts. AD[7:0] define the least
significant byte, and AD[31:24] define the
most significant byte.

C_BE[3:0]

1, 15, 26,
39

A1, F3, H3,
K4

T/S

8 mA
PCI

Bus Command and Byte Enables are
multiplexed on the same PCI pins.
During the address phase of a
transaction, C_BE[3:0]/ define the bus
command. During the data phase,
C_BE[3:0]/ are used as byte enables.
The byte enables determine which byte
lanes carry meaningful data. C_BE[0]/
applies to byte 0, and C_BE[3]/ to byte 3.

PAR

T/S

8 mA
PCI

Parity is the even parity bit that protects
the AD[31:0] and C_BE[3:0]/ lines.
During the address phase, both the
address and command bits are covered.
During data phase, both data and byte
enables are covered.

PCI Bus Interface Signals

3-5

3.3.3 Interface Control Signals
Table 3.4 describes the Interface Control signals.
Table 3.4

Interface Control Signals

Name

PQFP BGA

Type

FRAME/

S/T/S 8 mA PCI Cycle Frame is driven by the current master to indicate
the beginning and duration of an access. FRAME/ is
asserted to indicate that a bus transaction is beginning.
While FRAME/ is deasserted, either the transaction is
in the final data phase or the bus is idle.

TRDY/

S/T/S 8 mA PCI Target Ready indicates the target agent’s (selected
device’s) ability to complete the current data phase of
the transaction. TRDY/ is used with IRDY/. A data
phase is completed on any clock when used with
IRDY/. A data phase is completed on any clock when
both TRDY/ and IRDY/ are sampled asserted. During a
read, TRDY/ indicates that valid data is present on
AD[31:0]. During a write, it indicates that the target is
prepared to accept data. Wait cycles are inserted until
both IRDY/ and TRDY/ are asserted together.

IRDY/

S/T/S 8 mA PCI Initiator Ready indicates the initiating agent’s (bus
master’s) ability to complete the current data phase of
the transaction. IRDY/ is used with TRDY/. A data
phase is completed on any clock when both IRDY/ and
TRDY/ are sampled asserted. During a write, IRDY/
indicates that valid data is present on AD[31:0]. During
a read, it indicates that the master is prepared to
accept data. Wait cycles are inserted until both IRDY/
and TRDY/ are asserted together.

STOP/

S/T/S 8 mA PCI Stop indicates that the selected target is requesting
the master to stop the current transaction.

DEVSEL/ 20

S/T/S 8 mA PCI Device Select indicates that the driving device has
decoded its address as the target of the current
access. As an input, it indicates to a master whether
any device on the bus has been selected.

IDSEL

3-6

Strength Description

N/A

Signal Descriptions

Initialization Device Select is used as a chip select in
place of the upper 24 address lines during
configuration read and write transactions.

3.3.4 Arbitration Signals
Table 3.5 describes Arbitration signals.
Table 3.5

Arbitration Signals

Name

PQFP

BGA Type Strength Description

REQ/

148

GNT/

147

8 mA PCI Request indicates to the system arbiter that this agent
desires use of the PCI bus. This is a point-to-point signal.
Every master has its own REQ/ signal.
N/A

Grant indicates to the agent that access to the PCI bus
has been granted. This is a point-to-point signal. Every
master has its own GNT/ signal.

3.3.5 Error Reporting Signals
Table 3.6 describes the Error Reporting signals.
Table 3.6

Error Reporting Signals

Name

PQFP

BGA

Type

Strength Description

PERR/

S/T/
S

8 mA PCI Parity Error may be pulsed active by an agent that
detects a data parity error. PERR/ can be used by any
agent to signal data corruption. However, on detection of
a PERR/ pulse, the central resource may generate a
nonmaskable interrupt to the host CPU, which often
implies the system is unable to continue operation once
error processing is complete.

SERR/

143

8 mA PCI System Error is an open drain output used to report
address parity errors as well as critical errors other than
parity.

PCI Bus Interface Signals

3-7

3.3.6 Interrupt Signal
Table 3.7 describes the Interrupt signal.
Table 3.7

Interrupt Signal

Name PQFP BGA
IRQ/

Type
O

Strength Description
8 mA PCI Interrupt Request. This signal, when asserted LOW,
indicates that an interrupting condition has occurred and
that service is required from the host CPU. The output
drive of this pin is open drain.

1. See Register 0x4D, SCSI Test One (STEST1) in Chapter 4 for additional information on this signal.

3.4 SCSI Bus Interface Signals
The SCSI Bus Interface signals section contains tables describing the
signals for the following signal groups: SCSI Bus Interface Signals, SCSI
Signals, and SCSI Control Signals.

3.4.1 SCSI Bus Interface Signal
Table 3.8 describes the SCSI Bus Interface signal.
Table 3.8

SCSI Bus Interface Signal

Name PQFP

BGA Type Strength Description

SCLK

3-8

N/A

Signal Descriptions

SCSI Clock is used to derive all SCSI-related timings. The
speed of this clock is determined by the application’s
requirements. In some applications, SCLK may be sourced
internally from the PCI bus clock (CLK). If SCLK is
internally sourced, then the SCLK pin should be tied low.

3.4.2 SCSI Signals
Table 3.9 describes the SCSI signals.
Table 3.9

SCSI Signals

Name

PQFP

BGA

SD[15:0]

113, 115–17, 85–87, 89,
102, 103, 105–108, 110,
111

D13, E10, C13, D11, J9,
L13, K11, J10, G10, G9,
F13, F11–9, E12, E11

I/O

48 mA SCSI SCSI Data.

F8, G13

I/O

48 mA SCSI SCSI Parity.

SDP[1:0] 112, 101

Type

Strength

Description

3.4.3 SCSI Control Signals
Table 3.10 describes the SCSI Control signals.
Table 3.10

SCSI Control Signals

Name

PQFP

BGA Type Strength Description

SCD

J12

I/O

48 mA

SCSI phase line, command/data

SIO

K13

I/O

48 mA

SCSI phase line, input/output.

SMSG 95

H11

I/O

48 mA

SCSI phase line, message.

SREQ

J11

I/O

48 mA

Data handshake line from target device.

SACK

H13

I/O

48 mA

Data handshake signal from the initiator device.

SBSY

I/O

48 mA

SCSI bus arbitration signal, busy.

SATN

100

G12

I/O

48 mA

SCSI Attention, the initiator is requesting a message out
phase.

SRST

H12

I/O

48 mA

SCSI bus reset.

SSEL

H10

I/O

48 mA

SCSI bus arbitration signal, select device.

SCSI Bus Interface Signals

3-9

3.5 GPIO Signals
Table 3.11 describes the SCSI GPIO signals.
Table 3.11

GPIO Signals

Name

PQFP

BGA Type Strength Description

GPIO0_FETCH/

I/O

8 mA

SCSI General Purpose I/O pin. Optionally,
when driven LOW, indicates that the next bus
request will be for an opcode fetch. This pin is
programmable at power-up through the MAD7
pin to serve as the data signal for the serial
EEPROM interface. This signal can also be
programmed to be driven LOW when the
LSI53C875A is active on the SCSI bus.

GPIO1_MASTER/ 54

I/O

8 mA

SCSI General Purpose I/O pin. Optionally,
when driven LOW, indicates that the
LSI53C875A is bus master. This pin is
programmable at power-up through the MAD7
pin to serve as the clock signal for the serial
EEPROM interface.

GPIO2

I/O

8 mA

SCSI General Purpose I/O pin. This pin
powers up as an input.

GPIO3

I/O

8 mA

SCSI General Purpose I/O pin. This pin
powers up as an input.

GPIO4

I/O

8 mA

SCSI General Purpose I/O pin. GPIO4
powers up as an output. (This pin may be used
as the enable line for VPP, the 12 V power
supply to the external flash memory interface.)

3-10

Signal Descriptions

3.6 ROM Flash and Memory Interface Signals
Table 3.12 describes the ROM Flash and Memory Interface signals.
Table 3.12

ROM Flash and Memory Interface Signals

Name

PQFP

BGA

Type Strength Description

MWE/

139

4 mA

Memory Write Enable. This pin is used as a write
enable signal to an external flash memory.

MCE/

141

4 mA

Memory Chip Enable. This pin is used as a chip
enable signal to an external EEPROM or flash
memory device.

MOE/

140

4 mA

Memory Output Enable. This pin is used as an
output enable signal to an external EEPROM or
flash memory during read operations. It is also
used to test the connectivity of the LSI53C875A
signals in test mode.

MAC/_
77
TESTOUT

L10

16 mA

Memory Access Control. This pin can be
programmed to indicate local or system memory
accessed (non-PCI applications). It is also used to
test the connectivity of the LSI53C875A signals in
test mode.

MAS0/

137

4 mA

Memory Address Strobe 0. This pin is used to
latch in the least significant address byte (bits [7:0])
of an external EEPROM or flash memory. Since
the LSI53C875A moves addresses eight bits at a
time, this pin connects to the clock of an external
bank of flip-flops which are used to assemble up to
a 20-bit address for the external memory.

MAS1/

136

4 mA

Memory Address Strobe 1. This pin is used to
latch in the most significant address byte (bits
[15:8]) of an external EEPROM or flash memory.
Since the LSI53C875A moves addresses eight bits
at a time, this pin connects to the clock of an
external bank of flip-flops which assemble up to a
20-bit address for the external memory.

ROM Flash and Memory Interface Signals

3-11

Table 3.12

ROM Flash and Memory Interface Signals (Cont.)

Name

PQFP

BGA

MAD[7:0]

59–62,
64–67

L7, M7,
N7, K7,
M8, N8,
L8, K8

Type Strength Description
I/O

4 mA

Memory Address/Data Bus. This bus is used in
conjunction with the memory address strobe pins
and external address latches to assemble up to a
20-bit address for an external EEPROM or flash
memory. This bus will put out the least significant
byte first and finishes with the most significant bits.
It is also used to write data to a flash memory or
read data into the chip from external EEPROM/
flash memory. These pins have static pull-downs.

3.7 Test Interface Signals
Table 3.13 describes Test Interface signals.
Table 3.13

Test Interface Signals

Name

PQFP

BGA

TEST_HSC/

126

A11

N/A

Test Halt SCSI Clock. For LSI Logic test purposes
only. Pulled HIGH internally. This signal can also
cause a full chip reset.

TCK

130

A10

N/A

Test Clock. This pin provides the clock for the JTAG
test logic.

TMS

N/A

Test Mode Select. The signal received at TMS is
decoded by the TAP controller to control JTAG test
operations. This pin has a static pull-down.

TDI

142

N/A

Test Data In. Serial test instructions are received by
the JTAG test logic at this pin. This pin has a static
pull-down.

TEST_RST/

127

C10

N/A

Test Reset. For test purposes only. Pulled HIGH
internally.

TDO

4 mA

Test Data Out. This pin is the serial output for test
instructions and data from the JTAG test logic.

TRST/

131

N/A

Test Reset. This pin provides a reset for JTAG Test
Logic. Pulled HIGH internally.

3-12

Type Strength Description

Signal Descriptions

3.8 Power and Ground Signals
Table 3.14 describes the Power and Ground signals.
Table 3.14

Power and Ground Signals

Name

PQFP

BGA

Type Strength Description

VSS_I/O

4, 10, 14, 18,
23, 27, 31, 37,
42, 48, 69, 79,
88, 93, 99,
104, 109, 114,
123, 133, 152,
158

A9, B11, D12,
E13, F12,
G11, J13,
K10, K12, N9

N/A

Ground for PCI bus
drivers/receivers, SCSI bus
drivers/receivers, local memory
interface drivers, and other I/O
pins.

VDD_I/O

8, 21, 33, 45,
63, 74, 84,
118, 128, 138,
155

B10, C12, D2,
D5, E8, G1,
J5, J7, K1,
L11, M10

N/A

Power for PCI bus
drivers/receivers, SCSI bus
drivers/receivers, local memory
interface drivers/receivers, and
other I/O pins.

VDD_CORE 51, 83, 149

A5, L5, L12

N/A

Power for core logic.

VSS_CORE

55, 80, 146

C6, L6, N12

N/A

Ground for core logic.

VDDA

129

N/A

Power for analog cells (clock
quadrupler and diffsense logic).

VSSA

132

N/A

Ground for analog cells (clock
quadrupler and diffsense logic).

72, 73, 75, 76,
78, 81, 82,
119–122, 124,
125, 134, 135

A12, A13, B2,
B3, B12, B13,
C3, C8, C11,
D1, D8, D10,
E9, F4-6, G5,
H4, H8, J3,
K3, K9, M2,
M4, M11-13,
N2, N10, N11,
N13

N/A

These pins have NO internal
connection.

Note:
The I/O driver pad rows and digital core have isolated power supplies as indicated by the “I/O”
and “CORE” extensions on their respective VSS and VDD names. These power and ground pins
should be connected directly to the primary power and ground planes of the circuit board. Bypass
capacitors of 0.01 µF should be applied between adjacent VSS and VDD pairs wherever possible.
Do not connect bypass capacitors between VSS and VDD pairs that cross power and ground bus
boundaries.

Power and Ground Signals

3-13

3.9 MAD Bus Programming
The MAD[7:0] pins, in addition to serving as the address/data bus for the
local memory interface, also are used to program power-up options for
the chip. A particular option is programmed allowing the internal
pull-down current sink to pull the pin LOW at reset or by connecting a
4.7 kΩ resistor between the appropriate MAD[x] pin and VSS. The
pull-down resistors require that HC or HCT external components are
used for the memory interface. The MAD[7:0] pins are sensed by internal
circuitry three PCI clock cycles after RST/ is deasserted.

•

MAD[7] Serial EEPROM programmable option. When allowed to be
pulled LOW by the internal pull-down current sink, the automatic data
download is enabled. When pulled HIGH by an external resistor, the
automatic data download is disabled. Please see Section 2.4, “Serial
EEPROM Interface,” in Chapter 2 and Subsystem ID and Subsystem
Vendor ID registers in Chapter 4 for additional information.

•

MAD[6:4] Reserved and may be left floating.

•

The MAD[3:1] pins are used to set the size of the external expansion
ROM device attached. Encoding for these pins are listed in
Table 3.15 (“0” indicates a pull-down resistor is attached, “1”
indicates a pull-up resistor is attached).

Table 3.15

3-14

Decode of MAD Pins

MAD[3:1]

Available Memory Space

000

16 Kbyte

001

32 Kbyte

010

64 Kbyte

011

128 Kbyte

100

256 Kbyte

101

512 Kbyte

110

1024 Kbyte

111

no external memory present

Signal Descriptions

•

The MAD[0] pin is the slow ROM pin. When pulled up, it enables two
extra cycles of data access time to allow use of slower memory
devices.

•

All MAD pins have internal pull-down resistors.

MAD Bus Programming

3-15

3-16

Signal Descriptions

Chapter 4
Registers

This chapter describes all LSI53C875A registers and is divided into the
following sections:

•

Section 4.1 “PCI Configuration Registers”

•

Section 4.2 “SCSI Registers”

•

Section 4.3 “64-Bit SCRIPTS Selectors”

•

Section 4.4 “Phase Mismatch Jump Registers”

In the register descriptions, the term “set” is used to refer to bits that are
programmed to a binary one. Similarly, the term “cleared” is used to refer
to bits that are programmed to a binary zero. Write any bits marked as
reserved to zero; mask all information read from them. Reserved bit
functions may change at any time. Unless otherwise indicated, all bits in
registers are active HIGH, that is, the feature is enabled by setting the
bit. The bottom row of every register diagram shows the default register
values, which are enabled after the chip is powered on or reset.
Reserved registers and bits are shaded in the register tables.

4.1 PCI Configuration Registers
The PCI Configuration registers are accessed by performing a
configuration read/write to the device with its IDSEL pin asserted and the
appropriate value in AD[10:8] during the address phase of the
transaction. The LSI53C875A responds to a binary value of 000b.
Table 4.1 describes the PCI configuration registers
All PCI-compliant devices must support the Vendor ID, Device ID,
Command, and Status registers. Support of other PCI-compliant
registers is optional. In the LSI53C875A, registers that are not supported
are not writable and return all zeros when read. Only those registers and

LSI53C875A PCI to Ultra SCSI Controller

4-1

bits that are currently supported by the LSI53C875A are described in this
chapter. Reserved bits should not be accessed.
Table 4.1

PCI Configuration Register Map

16 15

Device ID

Vendor ID

Status

Command
Class Code

Not Supported

Header Type

Latency Timer

0x00
0x04

Revision ID (Rev ID)

0x08

Cache Line Size

0x0C

Base Address Register Zero (I/O)

0x10

Base Address Register One (MEMORY) bits [31:0]

0x14

Base Address Register Two (SCRIPTS RAM)

0x18

Not Supported

0x1C

Not Supported

0x20

Not Supported

0x24

Reserved

0x28

Subsystem ID

Subsystem Vendor ID

0x2C

Expansion ROM Base Address

0x30

Reserved

Capabilities Pointer

0x34

Interrupt Pin

Interrupt Line

0x3C

Next Item Pointer

Capability ID

0x40

Reserved
Max_Lat

Min_Gnt

Power Management Capabilities (PMC)
Data

Bridge Support Extensions (PMCSR_BSE)

0x38

Power Management Control/Status (PMCSR)

0x44

Not Supported

0x48

Registers: 0x00–0x01
Vendor ID
Read Only
15

0
VID

VID

4-2

Registers

Vendor ID
[15:0]
This 16-bit register identifies the manufacturer of the
device. The Vendor ID is 0x1000.

Registers: 0x02–0x03
Device ID
Read Only
15

0
DID

DID

Device ID
[15:0]
This 16-bit register identifies the particular device. The
LSI53C875A Device ID is 0x0013.

Registers: 0x04–0x05
Command
Read/Write
15

9
R

EPER

WIE

EBM

EMS

EIS

The Command register provides coarse control over a device’s ability to
generate and respond to PCI cycles. When a zero is written to this
register, the LSI53C875A is logically disconnected from the PCI bus for
all accesses except configuration accesses.
R

Reserved

SERR/ Enable
8
This bit enables the SERR/ driver. SERR/ is disabled
when this bit is cleared. The default value of this bit is
zero. This bit and bit 6 must be set to report address
parity errors.

Reserved

EPER

Enable Parity Error Response
6
This bit allows the LSI53C875A to detect parity errors on
the PCI bus and report these errors to the system. Only
data parity checking is enabled and disabled with this bit.
The LSI53C875A always generates parity for the PCI
bus.

PCI Configuration Registers

[15:9]

4-3

4-4

Reserved

WIE

Write and Invalidate Enable
4
This bit allows the LSI53C875A to generate write and
invalidate commands on the PCI bus. The WIE bit in the
DMA Control (DCNTL) register must also be set for the
device to generate Write and Invalidate commands.

Reserved

EBM

Enable Bus Mastering
2
This bit controls the ability of the LSI53C875A to act as
a master on the PCI bus. A value of zero disables this
device from generating PCI bus master accesses. A
value of one allows the LSI53C875A to behave as a bus
master. The device must be a bus master in order to fetch
SCRIPTS instructions and transfer data.

EMS

Enable Memory Space
1
This bit controls the ability of the LSI53C875A to respond
to Memory space accesses. A value of zero disables the
device response. A value of one allows the LSI53C875A
to respond to Memory Space accesses at the address
range specified by Base Address Register One (MEMORY) and Base Address Register Two (SCRIPTS RAM)
registers in the PCI configuration space.

EIS

Enable I/O Space
0
This bit controls the LSI53C875A response to I/O space
accesses. A value of zero disables the device response.
A value of one allows the LSI53C875A to respond to I/O
Space accesses at the address range specified by the
Base Address Register Zero (I/O) register in the PCI
configuration space.

Registers

Registers: 0x06–0x07
Status
Read/Write
15

DPE SSE RMA RTA
0

DT[1:0]

DPR

5
R

NC
x

R
x

Reads to this register behave normally. Writes are slightly different in that
bits can be cleared, but not set. A bit is cleared whenever the register is
written, and the data in the corresponding bit location is a one. For
instance, to clear bit 15 and not affect any other bits, write the value
0x8000 to the register.
DPE

Detected Parity Error (from Slave)
15
This bit is set by the LSI53C875A whenever it detects a
data parity error, even if data parity error handling is
disabled.

SSE

Signaled System Error
14
This bit is set whenever the device asserts the SERR/
signal.

RMA

Received Master Abort (from Master)
13
A master device should set this bit whenever its
transaction (except for Special Cycle) is terminated with
Master Abort.

RTA

Received Target Abort (from Master)
A master device should set this bit whenever its
transaction is terminated by target abort.

Reserved

DT[1:0]

DEVSEL/ Timing
[10:9]
These bits encode the timing of DEVSEL/. These are
encoded as:

0b00

fast

0b01

medium

0b10

slow

0b11

reserved

PCI Configuration Registers

4-5

These bits are read only and should indicate the slowest
time that a device asserts DEVSEL/ for any bus
command except Configuration Read and Configuration
Write. The LSI53C875A supports a value of 0b01.
DPR

Data Parity Error Reported
8
This bit is set when all of the following conditions are met:

• The bus agent asserted PERR/ itself or observed
PERR/ asserted.

• The agent setting this bit acted as the bus master for
the operation in which the error occurred.

• The Parity Error Response bit in the Command
register is set.
R

Reserved

[7:5]

New Capabilities
4
This bit is set to indicate a list of extended capabilities
such as PCI Power Management. This bit is read only.

Reserved

[3:0]

0
RID

RID

4-6

Registers

Revision ID
[7:0]
This register contains the current revision level of the
device.

Registers: 0x09–0x0B
Class Code
Read Only
23

0
CC

Class Code
[23:0]
This 24-bit register is used to identify the generic function
of the device. The upper byte of this register is a base
class code, the middle byte is a subclass code, and the
lower byte identifies a specific register level programming
interface. The value of this register is 0x010000, which
identifies a SCSI controller.

0
CLS

CLS

Cache Line Size
[7:0]
This register specifies the system cache line size in units
of 32-bit words. The value in this register is used by the
device to determine whether to use Write and Invalidate
or Write commands for performing write cycles, and
whether to use Read, Read Line, or Read Multiple
commands for performing read cycles as a bus master.
Devices participating in the caching protocol use this field
to know when to retry burst accesses at cache line
boundaries. These devices can ignore the PCI cache
support lines (SDONE and SB0/) when this register is
cleared to 0. If this register is programmed to a number
which is not a power of 2, the device will not use PCI
performance commands to perform data transfers.

PCI Configuration Registers

4-7

0
LT

Latency Timer
[7:0]
The Latency Timer register specifies, in units of PCI bus
clocks, the value of the Latency Timer for this PCI bus
master. The LSI53C875A supports this timer. All eight
bits are writable, allowing latency values of 0–255 PCI
clocks. Use the following equation to calculate an
optimum latency value for the LSI53C875A.
Latency = 2 + (Burst Size x (typical wait states + 1))
Values greater than optimum are also acceptable.

0
HT

Not Supported

Registers

Header Type
[7:0]
This register identifies the layout of bytes 0x10 through
0x3F in configuration space and also whether or not the
device contains multiple functions. Since the LSI53C875A
is not a multifunction controller the value of this register
is 0x00.

4-8

Registers: 0x10–0x13
Base Address Register Zero (I/O)
Read/Write
31

0
BAR0

BAR0

Base Address Register Zero - I/O
[31:0]
This base address register is used to map the operating
register set into I/O space. The LSI53C875A requires
256 bytes of I/O space for this base address register. It
has bit zero hardwired to one. Bit 1 is reserved and
returns a zero on all reads, and the other bits are used
to map the device into I/O space. For detailed information
on the operation of this register, refer to the PCI 2.2
specification.

Registers: 0x14–0x17
Base Address Register One (MEMORY)
Read/Write
31

0
BAR1

BAR1

Base Address Register One
[31:0]
This base address register maps SCSI operating
registers into memory space. This device requires
1024 bytes of address space for this base register. This
register has bits [9:0] hardwired to 0b0000000000. The
default value of this register is 0x00000000. For detailed
information on the operation of this register, refer to the
PCI 2.2 specification.

PCI Configuration Registers

4-9

Registers: 0x18–0x1B
Base Address Register Two (SCRIPTS RAM)
Read/Write
31

0
BAR2

BAR2

Base Address Register Two
[31:0]
This base register is used to map the SCRIPTS RAM into
memory space. The default value of this register is
0x00000000. The LSI53C875A points to 4096 bytes of
address space with this register. This register has bits
[11:0] hardwired to 0b000000000000. For detailed
information on the operation of this register, refer to the
PCI 2.2 specification.

Registers: 0x1C–0x27
Not Supported

Registers: 0x28–0x2B
Reserved

Registers: 0x2C–0x2D
Subsystem Vendor ID
Read Only
15

0
SVID

If MAD[7] HIGH Default
0

If MAD[7] LOW See Description Default
x

SVID

4-10

Registers

Subsystem Vendor ID
[15:0]
This 16-bit register is used to uniquely identify the vendor
manufacturing the add-in board or subsystem where this
PCI device resides. It provides a mechanism for an
add-in card vendor to distinguish its cards from another
vendor’s cards, even if the cards have the same PCI

controller installed on them (and therefore the same
Vendor ID and Device ID).
If the external serial EEPROM interface is enabled
(MAD[7] LOW), this register is automatically loaded at
power-up from the external serial EEPROM and will
contain the value downloaded from the serial EEPROM
or a value of 0x0000 if the download fails.
If the external serial EEPROM interface is disabled
(MAD[7] HIGH), this register returns a value of 0x1000
(LSI Logic Vendor ID). The 16-bit value that should be
stored in the external serial EEPROM for this register is
the vendor’s PCI Vendor ID and must be obtained from
the PCI Special Interest Group (SIG). Please see Section
2.4, “Serial EEPROM Interface,” in Chapter 2 for more
information on downloading a value for this register.

Registers: 0x2E–0x2F
Subsystem ID
Read Only
15

0
SID

If MAD[7] HIGH Default
0

If MAD[7] LOW See Description Default
x

SID

Subsystem ID
[15:0]
This 16-bit register is used to uniquely identify the add-in
board or subsystem where this PCI device resides. It
provides a mechanism for an add-in card vendor to
distinguish its cards from one another even if the cards
have the same PCI controller installed on them (and
therefore the same Vendor ID and Device ID).
If the external serial EEPROM interface is enabled
(MAD[7] is LOW), this register is automatically loaded at
power-up from the external serial EEPROM and will
contain the value downloaded from the serial EEPROM
or a value of 0x0000 if the download fails.
If the external serial EEPROM is disabled (MAD[7] pulled
HIGH), the register returns a value of 0x1000. The 16-bit

PCI Configuration Registers

4-11

value that should be stored in the external serial
EEPROM is vendor specific. Please see the Section 2.4
“Serial EEPROM Interface” in Chapter 2 for additional
information on downloading a value for this register.

Registers: 0x30–0x33
Expansion ROM Base Address
Read/Write
31

0
ERBA[31:0]

ERBA

Expansion ROM Base Address
[31:0]
This four-byte register handles the base address and size
information for the expansion ROM. It functions exactly
like the Base Address Register Zero (I/O) and One
(Memory) registers, except that the encoding of the bits
is different. The upper 21 bits correspond to the upper
21 bits of the expansion ROM base address.
The expansion ROM Enable bit, bit 0, is the only bit
defined in this register. This bit is used to control whether
or not the device accepts accesses to its expansion
ROM. When the bit is set, address decoding is enabled,
and a device is used with or without an expansion ROM
depending on the system configuration. To access the
external memory interface, also set the Memory Space
bit in the Command register.
The host system detects the size of the external memory
by first writing the Expansion ROM Base Address register
with all ones and then reading back the register. The
LSI53C875A responds with zeros in all don’t care
locations. The ones in the remaining bits represent the
binary version of the external memory size. For example,
to indicate an external memory size of 32 Kbytes, this
register, when written with ones and read back, returns
ones in the upper 17 bits.
The size of the external memory is set through MAD[3:1].
Please see the section on MAD Bus Programming for the
possible size encodings available.

4-12

Registers

0
CP

Capabilities Pointer
[7:0]
This register indicates that the first extended capability
register is located at offset 0x40 in the PCI Configuration.

Registers: 0x35–0x3B
Reserved

0
IL

Interrupt Line
[7:0]
This register is used to communicate interrupt line routing
information. POST software writes the routing information
into this register as it configures the system. The value in
this register tells which input of the system interrupt
controller(s) the device’s interrupt pin is connected to.
Values in this register are specified by system
architecture.

PCI Configuration Registers

4-13

0
IP

Interrupt Pin
[7:0]
This register indicates which interrupt pin the device
uses. Its value is set to 0x01 for the INTA/ signal.

0
MG

MIN_GNT
[7:0]
This register is used to specify the desired settings for
latency timer values. Min_Gnt is used to specify how long
a burst period the device needs. The value specified in
this register is in units of 0.25 microseconds. The
LSI53C875A sets this register to 0x11.

0
ML

4-14

Registers

MAX_LAT
[7:0]
This register is used to specify the desired settings for
latency timer values. Max_Lat is used to specify how
often the device needs to gain access to the PCI bus.
The value specified in this register is in units of
0.25 microseconds. The LSI53C875A sets this register to
0x40.

0
CID

CID

Cap_ID
[7:0]
This register indicates the type of data structure currently
being used. It is set to 0x01, indicating the Power
Management Data Structure.

0
NIP

NIP

Next_Item_Ptr
[7:0]
Bits [7:0] contain the offset location of the next item in the
controller’s capabilities list. The LSI53C875A has these
bits set to zero indicating no further extended capabilities
registers exist.

Registers: 0x42–0x43
Power Management Capabilities (PMC)
Read Only
15

11
PMES

PMES

D2S D1S
0

6
R

DSI APS PMEC
x

0
VER[2:0]

PME_Support
[15:11]
Bits [15:11] define the power management states in
which the LSI53C875A will assert the PME pin. These
bits are all set to zero because the LSI53C875A does not
provide a PME signal.

PCI Configuration Registers

4-15

D2S

D2_Support
10
The LSI53C875A sets this bit to indicate support for
power management state D2.

D1S

D1_Support
The LSI53C875A sets this bit to indicate support for
power management state D1.

Reserved

DSI

Device Specific Initialization
5
This bit is cleared to indicate that the LSI53C875A
requires no special initialization before the generic class
device driver is able to use it.

APS

Auxiliary Power Source
4
Because the LSI53C875A does not provide a PME
signal, this bit is cleared, indicating that no auxiliary
power source is required to support the PME signal in the
D3cold power management state.

PMEC

PME Clock
Bit 3 is cleared because the LSI53C875A does not
provide a PME pin.

VER[2:0]

Version
[2:0]
These three bits are set to 010 to indicate that the
LSI53C875A complies with Revision 1.1 of the PCI Power
Management Interface Specification.

[8:6]

Registers: 0x44–0x45
Power Management Control/Status (PMCSR)
Read/Write
15

14 13 12

PST DSCL
0

PST

4-16

Registers

DSLT
0

PEN
0

R
x

PWS[1:0]
x

PME Status
15
The LSI53C875A always returns a zero for this bit,
indicating that PME signal generation is not supported
from D3cold.

DSCL

Data_Scale
[14:13]
The LSI53C875A does not support the data register.
Therefore, these two bits are always cleared.

DSLT

Data_Select
[12:9]
The LSI53C875A does not support the data register.
Therefore, these four bits are always cleared.

PEN

PME_Enable
The LSI53C875A always returns a zero for this bit to
indicate that PME assertion is disabled.

Reserved

PWS[1:0]

Power State
[1:0]
Bits [1:0] are used to determine the current power state
of the LSI53C875A. They are used to place the
LSI53C875A in a new power state. Power states are
defined as:

[7:2]

0b00

0b01

0b10

0b11

D3hot

See Section 2.5, “Power Management,” in Chapter 2 for
descriptions of the Power Management States.

0
BSE

BSE

Bridge Support Extensions
[7:0]
This register indicates PCI Bridge specific functionality.
The LSI53C875A does not support extensions and
always returns 0x00.

PCI Configuration Registers

4-17

0
DATA

DATA

Data
[7:0]
This register provides an optional mechanism for the
function to report state-dependent operating data. The
LSI53C875A does not use this register and always
returns 0x00.

4.2 SCSI Registers
The control registers for the SCSI core are directly accessible from the
PCI bus using Memory or I/O mapping. The address map of the SCSI
registers is shown in Table 4.2.
Note:

4-18

Registers

The only registers that the host CPU can access while the
LSI53C875A is executing SCRIPTS are the Interrupt Status
Zero (ISTAT0), Interrupt Status One (ISTAT1) and
Mailbox Zero (MBOX0), Mailbox One (MBOX1) registers;
attempts to access other registers interfere with the
operation of the chip. However, all operating registers are
accessible with SCRIPTS. All read data is synchronized
and stable when presented to the PCI bus.

Table 4.2

SCSI Register Address Map

16 15
SCNTL3
GPREG0
SBCL
SSTAT2

SCNTL2
SDID
SSID
SSTAT1

MBOX1
CTEST3

MBOX0
CTEST2

CTEST6
DCMD

CTEST5

0
SCNTL1
SXFER
SOCL
SSTAT0

SCNTL0
SCID
SFBR
DSTAT

ISTAT1
CTEST1

ISTAT0
CTEST0

CTEST4
DBC

DFIFO

DIEN

DMODE

SIEN1
SWIDE
STIME1
STEST1

SIEN0
SLPAR
STIME0
STEST0

DSA

TEMP

DNAD
DSP
DSPS
SCRATCH A
DCNTL

SBR
ADDER

SIST1
GPCNTL0
RESPID1
STEST3
Reserved
CCNTL1
Reserved

Reserved

SIST0
MACNTL
RESPID0
STEST2
STEST4
CCNTL0
Reserved

SCRATCH B
SCRATCH C–SCRATCH R
MMRS
MMWS
SFS
DRS
SBMS
DBMS
DNAD64
Reserved
PMJAD1
PMJAD2
RBC
UA
ESA
IA
SBC
CSBC
Reserved

SCSI Registers

SIDL
SODL
SBDL

0x00
0x04
0x08
0x0C
0x10
0x14
0x18
0x1C
0x20
0x24
0x28
0x2C
0x30
0x34
0x38
0x3C
0x40
0x44
0x48
0x4C
0x50
0x54
0x58
0x5C
0x60–0x9F
0xA0
0xA4
0xA8
0xAC
0xB0
0xB4
0xB8
0xBC
0xC0
0xC4
0xC8
0xCC
0xD0
0xD4
0xD8
0xDC
0xE0–0xFF

4-19

6
ARB[1:0]

ARB[1:0]

START

WATN

EPC

AAP

TRG

Arbitration Mode Bits 1 and 0
ARB1

ARB0

Arbitration Mode

Simple arbitration

Reserved

Full arbitration, selection/reselection

[7:6]

Simple Arbitration
1. The LSI53C875A waits for a bus free condition to
occur.
2. It asserts SBSY/ and its SCSI ID (contained in the
SCSI Chip ID (SCID) register) onto the SCSI bus. If
the SSEL/ signal is asserted by another SCSI device,
the LSI53C875A deasserts SBSY/, deasserts its ID
and sets the Lost Arbitration bit (bit 3) in the SCSI
Status Zero (SSTAT0) register.
3. After an arbitration delay, the CPU should read the
SCSI Bus Data Lines (SBDL) register to check if a
higher priority SCSI ID is present. If no higher priority
ID bit is set, and the Lost Arbitration bit is not set, the
LSI53C875A wins arbitration.
4. Once the LSI53C875A wins arbitration, SSEL/ must be
asserted using the SCSI Output Control Latch (SOCL)
for a bus clear plus a bus settle delay (1.2 µs) before
a low level selection is performed.

4-20

Registers

Full Arbitration, Selection/Reselection
1. The LSI53C875A waits for a bus free condition.
2. It asserts SBSY/ and its SCSI ID (the highest priority
ID stored in the SCSI Chip ID (SCID) register) onto the
SCSI bus.
3. If the SSEL/ signal is asserted by another SCSI device
or if the LSI53C875A detects a higher priority ID, the
LSI53C875A deasserts SBSY, deasserts its ID, and
waits until the next bus free state to try arbitration
again.
4. The LSI53C875A repeats arbitration until it wins
control of the SCSI bus. When it wins, the Won
Arbitration bit is set in the SCSI Status Zero (SSTAT0)
register, bit 2.
5. The LSI53C875A performs selection by asserting the
following onto the SCSI bus: SSEL/, the target’s ID
(stored in the SCSI Destination ID (SDID) register),
and the LSI53C875A’s ID (stored in the SCSI Chip ID
(SCID) register).
6. After a selection is complete, the Function Complete
bit is set in the SCSI Interrupt Status Zero (SIST0)
register, bit 6.
7. If a selection time-out occurs, the Selection Time-Out
bit is set in the SCSI Interrupt Status One (SIST1)
register, bit 2.
START

SCSI Registers

Start Sequence
5
When this bit is set, the LSI53C875A starts the arbitration
sequence indicated by the Arbitration Mode bits. The
Start Sequence bit is accessed directly in
low level mode; during SCSI SCRIPTS operations, this bit
is controlled by the SCRIPTS processor. Do not start an
arbitration sequence if the connected (CON) bit in the
SCSI Control One (SCNTL1) register, bit 4, indicates that
the LSI53C875A is already connected to the SCSI bus.
This bit is automatically cleared when the arbitration
sequence is complete. If a sequence is aborted, check
bit 4 in the SCNTL1 register to verify that the
LSI53C875A is not connected to the SCSI bus.

4-21

WATN

Select with SATN/ on a Start Sequence
4
When this bit is set and the LSI53C875A is in the initiator
mode, the SATN/ signal is asserted during selection of a
SCSI target device. This is to inform the target that the
LSI53C875A has a message to send. If a selection
time-out occurs while attempting to select a target device,
SATN/ is deasserted at the same time SSEL/ is
deasserted. When this bit is cleared, the SATN/ signal is
not asserted during selection. When executing SCSI
SCRIPTS, this bit is controlled by the SCRIPTS
processor, but manual setting is possible in low level
mode.

EPC

Enable Parity Checking
3
When this bit is set, the SCSI data bus is checked for odd
parity when data is received from the SCSI bus in either
the initiator or target mode. If a parity error is detected,
bit 0 of the SCSI Interrupt Status Zero (SIST0) register is
set and an interrupt may be generated.
If the LSI53C875A is operating in the initiator mode and
a parity error is detected, assertion of SATN/ is optional,
but the transfer continues until the target changes phase.
When this bit is cleared, parity errors are not reported.

Reserved

AAP

Assert SATN/ on Parity Error
1
When this bit is set, the LSI53C875A automatically
asserts the SATN/ signal upon detection of a parity error.
SATN/ is only asserted in the initiator mode. The SATN/
signal is asserted before deasserting SACK/ during the
byte transfer with the parity error. Also set the Enable
Parity Checking bit for the LSI53C875A to assert SATN/
in this manner. A parity error is detected on data received
from the SCSI bus.
If the Assert SATN/ on Parity Error bit is cleared or the
Enable Parity Checking bit is cleared, SATN/ is not
automatically asserted on the SCSI bus when a parity
error is received.

TRG

4-22

Registers

Target Mode
0
This bit determines the default operating mode of the
LSI53C875A. The user must manually set the target or
initiator mode. This is done using the SCRIPTS language

(SET TARGET or CLEAR TARGET). When this bit is set, the
chip is a target device by default. When this bit is cleared,
the LSI53C875A is an initiator device by default.
Caution:

Writing this bit while not connected may cause the loss of
a selection or reselection due to the changing of target or
initiator modes.

EXC

ADB

DHP

CON

RST

AESP

IARB

SST

EXC

Extra Clock Cycle of Data Setup
7
When this bit is set, an extra clock period of data setup
is added to each SCSI data transfer. The extra data setup
time can provide additional system design margin, though
it affects the SCSI transfer rates. Clearing this bit disables
the extra clock cycle of data setup time. Setting this bit
only affects SCSI send operations.

ADB

Assert SCSI Data Bus
6
When this bit is set, the LSI53C875A drives the contents
of the SCSI Output Data Latch (SODL) register onto the
SCSI data bus. When the LSI53C875A is an initiator, the
SCSI I/O signal must be inactive to assert the SODL
contents onto the SCSI bus. When the LSI53C875A is a
target, the SCSI I/O signal must be active to assert the
SODL contents onto the SCSI bus. The contents of the
SCSI Output Data Latch (SODL) register can be asserted
at any time, even before the LSI53C875A is connected to
the SCSI bus. Clear this bit when executing SCSI
SCRIPTS. It is normally used only for diagnostic testing
or operation in low level mode.

DHP

Disable Halt on Parity Error or ATN (Target Only) 5
The DHP bit is only defined for target mode. When this
bit is cleared, the LSI53C875A halts the SCSI data
transfer when a parity error is detected or when the
SATN/ signal is asserted. If SATN/ or a parity error is
received in the middle of a data transfer, the LSI53C875A

SCSI Registers

4-23

may transfer up to three additional bytes before halting to
synchronize between internal core cells. During
synchronous operation, the LSI53C875A transfers data
until there are no outstanding synchronous offsets. If the
LSI53C875A is receiving data, any data residing in the
DMA FIFO is sent to memory before halting.
When this bit is set, the LSI53C875A does not halt the
SCSI transfer when SATN/ or a parity error is received.
CON

Connected
4
This bit is automatically set any time the LSI53C875A is
connected to the SCSI bus as an initiator or as a target.
It is set after the LSI53C875A successfully completes
arbitration or when it has responded to a bus initiated
selection or reselection. This bit is also set after the chip
wins simple arbitration when operating in low level mode.
When this bit is cleared, the LSI53C875A is not
connected to the SCSI bus.
The CPU can force a connected or disconnected
condition by setting or clearing this bit. This feature is
used primarily during loopback mode.

4-24

RST

Assert SCSI RST/ Signal
Setting this bit asserts the SRST/ signal. The SRST/
output remains asserted until this bit is cleared. The
25=µs minimum assertion time defined in the SCSI
specification must be timed out by the controlling
microprocessor or a SCRIPTS loop.

AESP

Assert Even SCSI Parity (force bad parity)
2
When this bit is set, the LSI53C875A asserts even parity.
It forces a SCSI parity error on each byte sent to the
SCSI bus from the chip. If parity checking is enabled,
then the LSI53C875A checks data received for odd parity.
This bit is used for diagnostic testing and is cleared for
normal operation. It is useful to generate parity errors to
test error handling functions.

IARB

Immediate Arbitration
1
Setting this bit causes the SCSI core to immediately
begin arbitration once a Bus Free phase is detected
following an expected SCSI disconnect. This bit is useful
for multithreaded applications. The ARB[1:0] bits in the

Registers

SCSI Control Zero (SCNTL0) register are set for full
arbitration and selection before setting this bit.
Arbitration is retried until won. At that point, the
LSI53C875A holds SBSY and SSEL asserted, and waits
for a select or reselect sequence. The Immediate
Arbitration bit is cleared automatically when the selection
or reselection sequence is completed, or times out.
An unexpected disconnect condition clears IARB with it
attempting arbitration. See the SCSI Disconnect
Unexpected bit (SCSI Control Two (SCNTL2), bit 7) for
more information on expected versus unexpected
disconnects.
It is possible to abort an immediate arbitration sequence.
First, set the Abort bit in the Interrupt Status Zero
(ISTAT0) register. Then one of two things eventually
happens:

• The Won Arbitration bit (SCSI Status Zero (SSTAT0),
bit 2) will be set. In this case, the Immediate
Arbitration bit needs to be cleared. This completes the
abort sequence and disconnects the chip from the
SCSI bus. If it is not acceptable to go to Bus Free
phase immediately following the arbitration phase, it is
possible to perform a low level selection instead.

• The abort completes because the LSI53C875A loses
arbitration. This is detected by the clearing of the
Immediate Arbitration bit. Do not use the Lost
Arbitration bit (SCSI Status Zero (SSTAT0), bit 3) to
detect this condition. In this case take no further
action.
SST

SCSI Registers

Start SCSI Transfer
0
This bit is automatically set during SCRIPTS execution
and should not be used. It causes the SCSI core to begin
a SCSI transfer, including SREQ/ and SACK/
handshaking. The determination of whether the transfer
is a send or receive is made according to the value
written to the I/O bit in SCSI Output Control Latch
(SOCL). This bit is self-clearing. Do not set it for low level
operation.

4-25

Caution:

Writing to this register while not connected may cause the
loss of a selection/reselection by clearing the Connected
bit.

SDU

CHM

SLPMD

SLPHBEN

WSS

WSR

SDU

SCSI Disconnect Unexpected
7
This bit is valid in the initiator mode only. When this bit is
set, the SCSI core is not expecting the SCSI bus to enter
the Bus Free phase. If it does, an unexpected disconnect
error is generated (see the Unexpected Disconnect bit in
the SCSI Interrupt Status Zero (SIST0) register, bit 2).
During normal SCRIPTS mode operation, this bit is set
automatically whenever the SCSI core is reselected, or
successfully selects another SCSI device. The SDU bit
should be cleared with a register write (move 0x00 to
SCNTL2) before the SCSI core expects a disconnect to
occur, normally prior to sending an Abort, Abort Tag, Bus
Device Reset, Clear Queue or Release Recovery
message, or before deasserting SACK/ after receiving a
Disconnect command or Command Complete message.

CHM

Chained Mode
6
This bit determines whether or not the SCSI core is
programmed for chained SCSI mode. This bit is
automatically set by the Chained Block Move (CHMOV)
SCRIPTS instruction and is automatically cleared by the
Block Move SCRIPTS instruction (MOVE).
Chained mode is primarily used to transfer consecutive
wide data blocks. Using chained mode facilitates partial
receive transfers and allows correct partial send behavior.
When this bit is set and a data transfer ends on an odd
byte boundary, the LSI53C875A stores the last byte in
the SCSI Wide Residue (SWIDE) register during a
receive operation, or in the SCSI Output Data Latch
(SODL) register during a send operation. This byte is

4-26

Registers

combined with the first byte from the subsequent transfer
so that a wide transfer is completed.
SLPMD

SLPAR Mode
5
If this bit is cleared, the SCSI Longitudinal Parity (SLPAR)
register functions as a byte-wide longitudinal parity
register. If this bit is set, the SLPAR functions as a
word-wide longitudinal parity function. The high or low
byte of the SLPAR word is accessible through the SLPAR
register. Which byte is accessible is controlled by the
SLPHBEN bit.

SLPHBEN

SLPAR High Byte Enable
4
If this bit is cleared, the low byte of the SLPAR word is
accessible through the SCSI Longitudinal Parity (SLPAR)
register. If this bit is set, the high byte of the SLPAR word
is present in the SLPAR register.

WSS

Wide SCSI Send
3
When read, this bit returns the value of the Wide SCSI
Send (WSS) flag. Asserting this bit clears the WSS flag.
This clearing function is self-clearing.
When the WSS flag is high following a wide SCSI send
operation, the SCSI core is holding a byte of “chain” data
in the SCSI Output Data Latch (SODL) register. This data
becomes the first low-order byte sent when married with
a high-order byte during a subsequent data send transfer.
Performing a SCSI receive operation clears this bit. Also,
performing any nonwide transfer clears this bit.

Vendor Unique Enhancements, Bit 0
2
This bit is a read only value indicating whether the group
code field in the SCSI instruction is standard or vendor
unique. If cleared, the bit indicates standard group codes;
if set, the bit indicates vendor unique group codes. The
value in this bit is reloaded at the beginning of all
asynchronous target receives.

Vendor Unique Enhancement, Bit 1
1
This bit is used to disable the automatic byte count reload
during Block Move instructions in the command phase. If
this bit is cleared, the device reloads the Block Move byte
count if the first byte received is one of the standard

SCSI Registers

4-27

group codes. If this bit is set, the device does not reload
the Block Move byte count, regardless of the group code.
WSR

Wide SCSI Receive
0
When read, this bit returns the value of the Wide SCSI
Receive (WSR) flag. Setting this bit clears the WSR flag.
This clearing function is self-clearing.
The WSR flag indicates that the SCSI core received data
from the SCSI bus, detected a possible partial transfer at
the end of a chained or nonchained block move
command, and temporarily stored the high-order byte in
the SCSI Wide Residue (SWIDE) register rather than
passing the byte out the DMA channel. The hardware
uses the WSR status flag to determine what behavior
must occur at the start of the next data receive transfer.
When the flag is set, the stored data in SWIDE may be
“residue” data, valid data for a subsequent data transfer,
or overrun data. The byte is read as normal data by
starting a data receive transfer.
Performing a SCSI send operation clears this bit. Also,
performing any nonwide transfer clears this bit.

USE
0

USE

4
SCF[2:0]

EWS
0

0
CCF[2:0]

Ultra SCSI Enable
7
Setting this bit enables Ultra SCSI synchronous transfers.
The default value of this bit is 0. This bit should remain
cleared if the LSI53C875A is not operating in Ultra SCSI
mode.
When this bit is set, the signal filtering period for SREQ/
and SACK/ automatically changes to 15 ns for Ultra
SCSI, regardless of the value of the Extend REQ/ACK
Filtering bit in the SCSI Test Two (STEST2) register.
Note:

4-28

Registers

Set this bit to achieve Ultra SCSI transfer rates in legacy
systems that use an 80 MHz clock.

SCF[2:0]

Synchronous Clock Conversion Factor
[6:4]
These bits select a factor by which the frequency of
SCLK is divided before being presented to the
synchronous SCSI control logic. Write these to the same
value as the Clock Conversion Factor bits below unless
fast SCSI operation is desired. See the SCSI Transfer
(SXFER) register description for examples of how the
SCF bits are used to calculate synchronous transfer
periods. See the table under the description of bits [7:5]
of the SXFER register for the valid combinations.

EWS

Enable Wide SCSI
3
When this bit is clear, all information transfer phases are
assumed to be eight bits, transmitted on SD[7:0]/ and
SDP0/. When this bit is asserted, data transfers are done
16 bits at a time, with the least significant byte on
SD[7:0]/ and SDP0/ and the most significant byte on
SD[15:8]/, SDP1/. Command, Status, and Message
phases are not affected by this bit.

CCF[2:0]

Clock Conversion Factor
[2:0]
These bits select a factor by which the frequency of
SCLK is divided before being presented to the SCSI core.
The synchronous portion of the SCSI core can be run at
a different clock rate for fast SCSI, using the
Synchronous Clock Conversion Factor bits. The bit
encoding is displayed in the table below. All other
combinations are reserved.

Note:

SCF2
CCF2

SCF1
CCF1

SCF0
CCF0

Factor
Frequency

SCSI Clock
(MHz)

SCLK/3

50.01–75.0

SCLK/1

16.67–25.0

SCLK/1.5

25.01–37.5

SCLK/2

37.51–50.0

SCLK/3

50.01–75.0

SCLK/4

75.01–80.00

SCLK/6

120

SCLK/8

160

It is important that these bits are set to the proper values
to guarantee that the LSI53C875A meets the SCSI timings
as defined by the ANSI specification.

SCSI Registers

4-29

RRE

SRE

0
ENC

Reserved

RRE

Enable Response to Reselection
6
When this bit is set, the LSI53C875A is enabled to
respond to bus-initiated reselection at the chip ID in the
Response ID Zero (RESPID0) and Response ID One
(RESPID1) registers. Note that the chip does not
automatically reconfigure itself to the initiator mode as a
result of being reselected.

SRE

Enable Response to Selection
5
When this bit is set, the LSI53C875A is able to respond
to bus-initiated selection at the chip ID in the RESPID0
and RESPID1 registers. Note that the chip does not
automatically reconfigure itself to target mode as a result
of being selected.

Reserved

ENC

Encoded Chip SCSI ID
[3:0]
These bits are used to store the LSI53C875A encoded
SCSI ID. This is the ID which the chip asserts when
arbitrating for the SCSI bus. The IDs that the
LSI53C875A responds to when selected or reselected
are configured in the Response ID Zero (RESPID0) and
Response ID One (RESPID1) registers. The priority of
the 16 possible IDs, in descending order is:

Highest
7

4-30

Registers

Lowest
2

TP[2:0]
0

Note:

MO[4:0]

When using Table Indirect I/O commands, bits [7:0] of this
register are loaded from the I/O data structure.

TP[2:0]

SCSI Synchronous Transfer Period
[7:5]
These bits determine the SCSI synchronous transfer
period used by the LSI53C875A when sending
synchronous SCSI data in either the initiator or target
mode. These bits control the programmable dividers in
the chip.
TP2

TP1

TP0

XFERP

The synchronous transfer period the LSI53C875A should
use when transferring SCSI data is determined in the
following example:
The LSI53C875A is connected to a hard disk which can
transfer data at 10 Mbytes/s synchronously. The
LSI53C875A’s SCLK is running at 40 MHz. The
synchronous transfer period (SCSI Transfer (SXFER)) is
found as follows:
SXFERP = Period/SSCP + ExtCC
Period = 1 ÷ Frequency = 1 ÷ 10 Mbytes/s = 100 ns
SSCP = 1 ÷= SSCF = 1 ÷ 40 MHz = 25 ns

SCSI Registers

4-31

(This SCSI synchronous core clock is determined in
SCNTL3 bits [6:4], ExtCC = 1 if SCNTL1 bit 7 is asserted
and the LSI53C875A is sending data. ExtCC = 0 if the
LSI53C875A is receiving data.)
SXFERP = 100 ÷ 25 = 4
Where:
SXFERP

Synchronous transfer period.

SSCP

SCSI synchronous core period.

SSCF

SCSI synchronous core frequency.

ExtCC

Extra clock cycle of data setup.

Table 4.3 shows examples of synchronous transfer periods and rates for
SCSI-1.
Table 4.3

4-32

Examples of Synchronous Transfer Periods and Rates
for SCSI-1

CLK (MHz)

SCSI CLK ÷
SCNTL3
Bits [6:4]

XFERP
(SXFER
Bits [7:5])

Synch.
Transfer
Period (ns)

Synch.
Transfer Rate
(Mbytes/s)

66.67

180

5.55

66.67

225

4.44

160

6.25

200

37.50

1.5

160

6.25

33.33

1.5

180

5.55

160

6.25

200

16.67

240

4.17

Registers

Table 4.4 shows example transfer periods and rates for fast SCSI-2 and
Ultra SCSI.
Table 4.4

Example Transfer Periods and Rates for Fast SCSI-2
and Ultra SCSI

CLK (MHz)

SCSI CLK ÷
SCNTL3
Bits [6:4]

1601
1

XFERP

Synch.
Transfer
Period (ns)

Synch. Transfer
Rate
(Mbytes/s)

100

12.5

100

10.0

100

10.0

37.50

106.67

9.375

33.33

120

8.33

160

6.25

200

16.67

240

4.17

160

1. Only with 40 MHz clock.

MO[4:0]

SCSI Registers

Max SCSI Synchronous Offset
[4:0]
These bits describe the maximum SCSI synchronous
offset used by the LSI53C875A when transferring
synchronous SCSI data in either the initiator or target
mode. Table 4.5 describes the possible combinations and
their relationship to the synchronous data offset used by
the LSI53C875A. These bits determine the
LSI53C875A’s method of transfer for Data-In and
Data-Out phases only; all other information transfers
occur asynchronously.

4-33

Table 4.5

4-34

Maximum Synchronous Offset

MO4

MO3

MO2

MO1

MO0

Synchronous Offset

0-Asynchronous

Registers

R
x

ENC

Reserved

[7:4]

ENC

Encoded Destination SCSI ID
[3:0]
Writing these bits set the SCSI ID of the intended initiator
or target during SCSI reselection or selection phases,
respectively. When executing SCRIPTS, the SCRIPTS
processor writes the destination SCSI ID to this register.
The SCSI ID is defined by the user in a SCRIPTS Select
or Reselect instruction. The value written is the
binary-encoded ID. The priority of the 16 possible IDs, in
descending order, is:
Highest
7

Lowest
2

R
x

GPIO
x

Reads to this register will always yield the same values. A write to this
register will cause the data written to be output to the appropriate GPIO
pin if it is set to the output mode in the General Purpose Pin Control Zero
(GPCNTL0) register.
R

Reserved

GPIO

General Purpose I/O
[4:0]
These bits are programmed through the General Purpose
Pin Control Zero (GPCNTL0) register as inputs, outputs,
or to perform special functions. As an output, these pins
can be used to enable or disable external terminators. It

SCSI Registers

[7:5]

4-35

is also possible to program these signals as live inputs
and sense them through a SCRIPTS register to register
Move Instruction. GPIO4 may be used to enable or
disable VPP, the 12 Volt power supply to the external flash
memory. This bit powers up with the power to external
memory disabled. GPIO[3:0] default as inputs and GPIO4
defaults as an output pin. When configured as inputs, an
internal pull-down is enabled for GPIO[4:2]. For
GPIO[1:0], internal pull-ups are enabled.
LSI Logic software uses the GPIO[1:0] signals to access
serial EEPROM. GPIO1 is used as a clock, with the
GPIO0 pin serving as data.
LSI Logic software also reserves the use of GPIO[4:2]. If
there is a need to use GPIO[4:2] please check with LSI
Logic for additional information.

0
SFBR

SFBR

SCSI First Byte Received
[7:0]
This register contains the first byte received in any
asynchronous information transfer phase. For example,
when a LSI53C875A is operating in the initiator mode,
this register contains the first byte received in the
Message-In, Status phase, and Data-In phases.
When a Block Move instruction is executed for a
particular phase, the first byte received is stored in this
register, even if the present phase is the same as the last
phase. The first byte received for a particular input phase
is not valid until after a MOVE instruction is executed.
This register is also the accumulator for register readmodify-writes with the SFBR as the destination. This
allows bit testing after an operation.
The SFBR is not writable using the CPU, and therefore
not by a Memory Move. However, it can be loaded using
SCRIPTS Read/Write operations. To load the SFBR with

4-36

Registers

a byte stored in system memory, the byte must first be
moved to an intermediate LSI53C875A register (such as
a SCRATCH register), and then to the SFBR.
This register also contains the state of the lower eight bits
of the SCSI data bus during the Selection phase if the
COM bit in the DMA Control (DCNTL) register is clear.
If the COM bit is cleared, do not access this register
using SCRIPTS operations, as nondeterminate
operations may occur. This includes SCRIPTS
Read/Write operations and conditional transfer control
instructions that initialize the SFBR register.

REQ

ACK

BSY

SEL

ATN

MSG

C_D

I/O

REQ

Assert SCSI REQ/ Signal

ACK

Assert SCSI ACK/ Signal

BSY

Assert SCSI BSY/ Signal

SEL

Assert SCSI SEL/ Signal

ATN

Assert SCSI ATN/ Signal

MSG

Assert SCSI MSG/ Signal

C_D

Assert SCSI C_D/ Signal

I/O

Assert SCSI I_O/ Signal

This register is used primarily for diagnostic testing or programmed I/O
operation. It is controlled by the SCRIPTS processor when executing
SCSI SCRIPTS. SOCL is used only when transferring data using
programmed I/O. Some bits are set (1) or cleared (0) when executing
SCSI SCRIPTS. Do not write to the register once the LSI53C875A starts
executing normal SCSI SCRIPTS.

SCSI Registers

4-37

VAL
0

ENID
x

VAL

SCSI Valid
7
If VAL is asserted, then the two SCSI IDs are detected
on the bus during a bus-initiated selection or reselection,
and the encoded destination SCSI ID bits below are valid.
If VAL is deasserted, only one ID is present and the
contents of the encoded destination ID are meaningless.

Reserved

ENID

Encoded Destination SCSI ID
[3:0]
Reading the SSID register immediately after the
LSI53C875A is selected or reselected returns the
binary-encoded SCSI ID of the device that performed the
operation. These bits are invalid for targets that are
selected under the single initiator option of the SCSI-1
specification. This condition is detected by examining the
VAL bit above.

[6:4]

REQ

ACK

BSY

SEL

ATN

MSG

C_D

I_O

This register returns the SCSI control line status. A bit is set when the
corresponding SCSI control line is asserted. These bits are not latched;
they are a true representation of what is on the SCSI bus at the time the
register is read. The resulting read data is synchronized before being
presented to the PCI bus to prevent parity errors from being passed to
the system. This register is used for diagnostic testing or operation in low
level mode.

4-38

Registers

REQ

SREQ/ Status

ACK

SACK/ Status

BSY

SBSY/ Status

SEL

SSEL/ Status

ATN

SATN/ Status

MSG

SMSG/ Status

C_D

SC_D/ Status

I_O

SI_O/ Status

DFE

MDPE

ABRT

SSI

SIR

IID

Reading this register clears any bits that are set at the time the register
is read, but does not necessarily clear the register in case additional
interrupts are pending (the LSI53C875A stacks interrupts). The DIP bit
in the Interrupt Status Zero (ISTAT0) register is also cleared. It is possible
to mask DMA interrupt conditions individually through the DMA Interrupt
Enable (DIEN) register.
When performing consecutive 8-bit reads of the DSTAT, SCSI Interrupt
Status Zero (SIST0) and SCSI Interrupt Status One (SIST1) registers (in
any order), insert a delay equivalent to 12 CLK periods between the
reads to ensure that the interrupts clear properly. See Chapter 2,
“Functional Description” for more information on interrupts.
DFE

SCSI Registers

DMA FIFO Empty
7
This status bit is set when the DMA FIFO is empty. It is
possible to use it to determine if any data resides in the
FIFO when an error occurs and an interrupt is generated.
This bit is a pure status bit and does not cause an
interrupt.

4-39

MDPE

Master Data Parity Error
6
This bit is set when the LSI53C875A as a master detects
a data parity error, or a target device signals a parity error
during a data phase. This bit is completely disabled by
the Master Parity Error Enable bit (bit 3 of Chip Test Four
(CTEST4)).

Bus Fault
5
This bit is set when a PCI bus fault condition is detected.
A PCI bus fault can only occur when the LSI53C875A is
bus master, and is defined as a cycle that ends with a
Bad Address or Target Abort Condition.

ABRT

Aborted
4
This bit is set when an abort condition occurs. An abort
condition occurs when a software abort command is
issued by setting bit 7 of the Interrupt Status Zero
(ISTAT0) register.

SSI

Single Step Interrupt
3
If the Single Step Mode bit in the DMA Control (DCNTL)
register is set, this bit is set and an interrupt is generated
after successful execution of each SCRIPTS instruction.

SIR

SCRIPTS Interrupt Instruction Received
2
This status bit is set whenever an Interrupt instruction is
evaluated as true.

Reserved

IID

Illegal Instruction Detected
0
This status bit is set any time an illegal or reserved
instruction opcode is detected, whether the LSI53C875A
is operating in single step mode or automatically
executing SCSI SCRIPTS.

Any of the following conditions during instruction
execution also set this bit:

• The LSI53C875A is executing a Wait Disconnect
instruction and the SCSI REQ line is asserted without
a disconnect occurring.

• A Block Move instruction is executed with 0x000000
loaded into the DMA Byte Counter (DBC) register,
indicating there are zero bytes to move.

4-40

Registers

• During a Transfer Control instruction, the Compare
Data (bit 18) and Compare Phase (bit 17) bits are set
in the DMA Byte Counter (DBC) register while the
LSI53C875A is in target mode.

• During a Transfer Control instruction, the Carry Test
bit (bit 21) is set and either the Compare Data (bit 18)
or Compare Phase (bit 17) bit is set.

• A Transfer Control instruction is executed with the
reserved bit 22 set.

• A Transfer Control instruction is executed with the
Wait for Valid phase bit (bit 16) set while the chip is in
target mode.

• A Load/Store instruction is issued with the
memory address mapped to the operating registers of
the chip, not including ROM or RAM.

• A Load/Store instruction is issued when the
register address is not aligned with the memory
address.

• A Load/Store instruction is issued with bit 5 in the
DMA Command (DCMD) register cleared or bits 3 or
2 set.

• A Load/Store instruction when the count value in the
DMA Byte Counter (DBC) register is not set at 1 to 4.

• A Load/Store instruction attempts to cross a Dword
boundary.

• A Memory Move instruction is executed with one of
the reserved bits in the DMA Command (DCMD)
register set.

• A Memory Move instruction is executed with the
source and destination addresses not aligned.

• A 64-bit Table Indirect Block Move instruction is
executed with a selector index value greater than
0x16.

• If the Select with ATN/ bit 24 is set for any I/O
instruction other than a Select instruction.

SCSI Registers

4-41

4-42

ILF

ORF

OLF

AIP

LOA

WOA

RST

SDP0

ILF

SIDL Least Significant Byte Full
7
This bit is set when the least significant byte in the SCSI
Input Data Latch (SIDL) register contains data. Data is
transferred from the SCSI bus to the SCSI Input Data
Latch register before being sent to the DMA FIFO and
then to the host bus. The SIDL register contains SCSI
data received asynchronously. Synchronous data
received does not flow through this register.

ORF

SODR Least Significant Byte Full
6
This bit is set when the least significant byte in the SCSI
Output Data Register (SODR, a hidden buffer register
which is not accessible) contains data. The SODR is
used by the SCSI logic as a second storage register
when sending data synchronously. It is not readable or
writable by the user. It is possible to use this bit to
determine how many bytes reside in the chip when an
error occurs.

OLF

SODL Least Significant Byte Full
5
This bit is set when the least significant byte in the SCSI
Output Data Latch (SODL) contains data. The SODL
register is the interface between the DMA logic and the
SCSI bus. In synchronous mode, data is transferred from
the host bus to the SODL register, and then to the SCSI
Output Data Register (SODR, a hidden buffer register
which is not accessible) before being sent to the SCSI
bus. In asynchronous mode, data is transferred from the
host bus to the SODL register, and then to the SCSI bus.
The SODR buffer register is not used for asynchronous
transfers. It is possible to use this bit to determine how
many bytes reside in the chip when an error occurs.

Registers

AIP

Arbitration in Progress
4
Arbitration in Progress (AIP = 1) indicates that the
LSI53C875A has detected a Bus Free condition, asserted
SBSY, and asserted its SCSI ID onto the SCSI bus.

LOA

Lost Arbitration
3
When set, LOA indicates that the LSI53C875A has
detected a bus free condition, arbitrated for the SCSI bus,
and lost arbitration due to another SCSI device asserting
the SSEL/ signal.

WOA

Won Arbitration
2
When set, WOA indicates that the LSI53C875A has
detected a Bus Free condition, arbitrated for the SCSI
bus and won arbitration. The arbitration mode selected in
the SCSI Control Zero (SCNTL0) register must be full
arbitration and selection to set this bit.

RST

SCSI RST/ Signal
1
This bit reports the current status of the SCSI RST/
signal, and the SRST signal (bit 6) in the Interrupt Status
Zero (ISTAT0) register. This bit is not latched and may
change as it is read.

SDP0

SCSI SDP0/ Parity Signal
0
This bit represents the active HIGH current status of the
SCSI SDP0/ parity signal. This signal is not latched and
may change as it is read.

4
FF[3:0]

FF[3:0]

SCSI Registers

SDP0L

MSG

C_D

I_O

FIFO Flags
[7:4]
These four bits, along with SCSI Status Two (SSTAT2)
bit 4, define the number of bytes or words that currently
reside in the LSI53C875A’s SCSI synchronous data FIFO
as shown in Table 4.6. These bits are not latched and
they will change as data moves through the FIFO. The
SCSI FIFO can hold up to 31 bytes for narrow SCSI

4-43

synchronous data transfers, or up to 31 words for wide.
Values over 31 will not occur.
Table 4.6

4-44

SCSI Synchronous Data FIFO Word Count

FF4
(SSTAT2 bit 4)

FF3

FF2

FF1

FF0

Bytes or Words
in the
SCSI FIFO

Registers

Table 4.6

SCSI Synchronous Data FIFO Word Count (Cont.)

FF4
(SSTAT2 bit 4)

FF3

FF2

FF1

FF0

Bytes or Words
in the
SCSI FIFO

SDP0L

Latched SCSI Parity
3
This bit reflects the SCSI parity signal (SDP0/),
corresponding to the data latched in the SCSI Input Data
Latch (SIDL). It changes when a new byte is latched into
the least significant byte of the SIDL register. This bit is
active HIGH, in other words, it is set when the parity
signal is active.

MSG

SCSI MSG/ Signal

C_D

SCSI C_D/ Signal

I_O

SCSI I_O/ Signal
0
These three SCSI phase status bits (MSG, C_D, and
I_O) are latched on the asserting edge of SREQ/ when
operating in either the initiator or target mode. These bits
are set when the corresponding signal is active. They are
useful when operating in the low level mode.

SCSI Registers

4-45

4-46

ILF1

ORF1

OLF1

FF4

SPL1

LDSC

SDP1

ILF1

SIDL Most Significant Byte Full
7
This bit is set when the most significant byte in the SCSI
Input Data Latch (SIDL) contains data. Data is transferred
from the SCSI bus to the SCSI Input Data Latch register
before being sent to the DMA FIFO and then to the host
bus. The SIDL register contains SCSI data received
asynchronously. Synchronous data received does not
flow through this register.

ORF1

SODR Most Significant Byte Full
6
This bit is set when the most significant byte in the SCSI
Output Data register (SODR, a hidden buffer register
which is not accessible) contains data. The SODR
register is used by the SCSI logic as a second storage
register when sending data synchronously. It is not
accessible to the user. This bit is used to determine how
many bytes reside in the chip when an error occurs.

OLF1

SODL Most Significant Byte Full
5
This bit is set when the most significant byte in the SCSI
Output Data Latch (SODL) contains data. The SODL
register is the interface between the DMA logic and the
SCSI bus. In synchronous mode, data is transferred from
the host bus to the SODL register, and then to the SCSI
Output Data register (SODR, a hidden buffer register
which is not accessible) before being sent to the SCSI
bus. In asynchronous mode, data is transferred from the
host bus to the SODL register, and then to the SCSI bus.
The SODR buffer register is not used for asynchronous
transfers. It is possible to use this bit to determine how
many bytes reside in the chip when an error occurs.

FF4

FIFO Flags, Bit 4
4
This is the most significant bit in the SCSI FIFO Flags
field, when concatenated with bits [7:4] (FF[3:0]) in SCSI
Status One (SSTAT1). For a complete description of this

Registers

field, see the definition for SCSI Status One (SSTAT1)
bits [7:4].
SPL1

Latched SCSI Parity for SD[15:8]
3
This active HIGH bit reflects the SCSI odd parity signal
corresponding to the data latched into the most
significant byte in the SCSI Input Data Latch (SIDL)
register.

Reserved

LDSC

Last Disconnect
1
This bit is used in conjunction with the Connected (CON)
bit in SCSI Control One (SCNTL1). It allows the user to
detect the case in which a target device disconnects, and
then some SCSI device selects or reselects the
LSI53C875A. If the Connected bit is asserted and the
LDSC bit is asserted, a disconnect is indicated. This bit
is set when the Connected bit in SCNTL1 is off. This bit
is cleared when a Block Move instruction is executed
while the Connected bit in SCNTL1 is on.

SDP1

SCSI SDP1 Signal
0
This bit represents the active HIGH current state of the
SCSI SDP1 parity signal. It is unlatched and may change
as it is read.

Registers: 0x10–0x13
Data Structure Address (DSA)
Read/Write
31

0
DSA

DSA

Data Structure Address
[31:0]
This 32-bit register contains the base address used for all
table indirect calculations. The DSA register is usually
loaded prior to starting an I/O, but it is possible for a
SCRIPTS Memory Move to load the DSA during the I/O.
During any Memory-to-Memory Move operation, the
contents of this register are preserved. The power-up
value of this register is indeterminate.

SCSI Registers

4-47

ABRT

SRST

SIGP

SEM

CON

INTF

SIP

DIP

This register is accessible by the host CPU while a LSI53C875A is
executing SCRIPTS (without interfering in the operation of the function).
It is used to poll for interrupts if hardware interrupts are disabled. Read
this register after servicing an interrupt to check for stacked interrupts.
ABRT

SRST

4-48

Registers

Abort Operation
7
Setting this bit aborts the current operation under
execution by the LSI53C875A. If this bit is set and an
interrupt is received, clear this bit before reading the DMA
Status (DSTAT) register to prevent further aborted
interrupts from being generated. The sequence to abort
any operation is:
1.

Set this bit.

Wait for an interrupt.

Read the Interrupt Status Zero (ISTAT0) and
Interrupt Status One (ISTAT1) registers.

If the SCSI Interrupt Pending bit is set, then read the
SCSI Interrupt Status Zero (SIST0) or SCSI Interrupt
Status One (SIST1) register to determine the cause
of the SCSI Interrupt and go back to Step 2.

If the SCSI Interrupt Pending bit is clear, and the
DMA Interrupt Pending bit is set, then write 0x00
value to this register.

Read the DMA Status (DSTAT) register to verify the
aborted interrupt and to see if any other interrupting
conditions have occurred.

Software Reset
6
Setting this bit resets the LSI53C875A. All operating
registers are cleared to their respective default values
and all SCSI signals are deasserted. Setting this bit does
not assert the SCSI RST/ signal. This reset does not

clear the ID Mode bit or any of the PCI configuration
registers. This bit is not self-clearing; it must be cleared
to clear the reset condition (a hardware reset also clears
this bit).
SIGP

Signal Process
5
SIGP is a R/W bit that is writable at any time, and polled
and reset using Chip Test Two (CTEST2). The SIGP bit
is used in various ways to pass a flag to or from a running
SCRIPTS instruction.
The only SCRIPTS instruction directly affected by the
SIGP bit is Wait for Selection/Reselection. Setting this bit
causes that instruction to jump to the alternate address
immediately. The instructions at the alternate jump
address should check the status of SIGP to determine
the cause of the jump. The SIGP bit is usable at any time
and is not restricted to the wait for selection/reselection
condition.

SEM

Semaphore
4
The SCRIPTS processor may set this bit using a
SCRIPTS register write instruction. An external processor
may also set it while the LSI53C875A is executing a
SCRIPTS operation. This bit enables the LSI53C875A to
notify an external processor of a predefined condition
while SCRIPTS are running. The external processor may
also notify the LSI53C875A of a predefined condition and
the SCRIPTS processor may take action while SCRIPTS
are executing.

CON

Connected
3
This bit is automatically set any time the LSI53C875A is
connected to the SCSI bus as an initiator or as a target.
It is set after successfully completing selection or when
the LSI53C875A responds to a bus-initiated selection or
reselection. It is also set after the LSI53C875A wins
arbitration when operating in low level mode. When this
bit is clear, the LSI53C875A is not connected to the SCSI
bus.

INTF

Interrupt-on-the-Fly
2
This bit is asserted by an INTFLY instruction during
SCRIPTS execution. SCRIPTS programs do not halt
when the interrupt occurs. This bit can be used to notify
a service routine, running on the main processor while

SCSI Registers

4-49

the SCRIPTS processor is still executing a SCRIPTS
program. If this bit is set when the Interrupt Status Zero
(ISTAT0) or Interrupt Status One (ISTAT1) registers are
read they are not automatically cleared. To clear this bit,
write it to a one. The reset operation is self-clearing.
Note:

If the INTF bit is set but SIP or DIP are not set, do not
attempt to read the other chip status registers. An
Interrupt-on-the-Fly interrupt must be cleared before
servicing any other interrupts indicated by SIP or DIP.
This bit must be written to one in order to clear it after it
has been set.

SIP

SCSI Interrupt Pending
1
This status bit is set when an interrupt condition is
detected in the SCSI portion of the LSI53C875A. The
following conditions cause a SCSI interrupt to occur:

• A phase mismatch (initiator mode) or SATN/ becomes
active (target mode)

• An arbitration sequence completes
• A selection or reselection time-out occurs
• The LSI53C875A is selected
• The LSI53C875A is reselected
• A SCSI gross error occurs
• An unexpected disconnect occurs
• A SCSI reset occurs
• A parity error is detected
• The handshake-to-handshake timer is expired
• The general purpose timer is expired
To determine exactly which condition(s) caused the
interrupt, read the SCSI Interrupt Status Zero (SIST0)
and SCSI Interrupt Status One (SIST1) registers.
DIP

DMA Interrupt Pending
0
This status bit is set when an interrupt condition is
detected in the DMA portion of the LSI53C875A. The
following conditions cause a DMA interrupt:

• A PCI parity error is detected

4-50

Registers

• A bus fault is detected
• An abort condition is detected
• A SCRIPTS instruction is executed in single step
mode

• A SCRIPTS interrupt instruction is executed
• An illegal instruction is detected
To determine exactly which condition(s) caused the
interrupt, read the DMA Status (DSTAT) register.

3
R

FLSH

SRUN

Reserved

[7:3]

FLSH

Flushing
2
Reading this bit monitors if the chip is currently flushing
data. If set, the chip is flushing data from the DMA FIFO.
If cleared, no flushing is occurring. This bit is read only
and writes will have no effect on the value of this bit.

SRUN

SCRIPTS Running
1
This bit indicates whether or not the SCRIPTS engine is
currently fetching and executing SCRIPTS instructions. If
this bit is set, the SCRIPTS engine is active.
If it is cleared, the SCRIPTS engine is not active.
This bit is read only and writes will have no effect on the
value of this bit.

SCSI Registers

SYNC_IRQD
0
Setting this bit disables the IRQ/ pin. Clearing this bit
enables normal operation of the IRQ/ pin. The function of
this bit is nearly identical to bit 1 of the DMA Control
(DCNTL) (0x3B) register except that if the IRQ/ is already
asserted and this bit is set, IRQ/ will remain asserted until
the interrupt is serviced. At this point the IRQ/ line will be
blocked for future interrupts until this bit is cleared. In

4-51

addition, this bit may be read and written while SCRIPTS
are executing.

0
MBOX0

MBOX0

Note:

Mailbox Zero
[7:0]
These are general purpose bits that may be read or
written while SCRIPTS are running. They also may be
read or written by the SCRIPTS processor.
The host and the SCRIPTS processor code could
potentially attempt to access the same mailbox byte at the
same time. Using one mailbox register as a read only and
the other as a write only will prevent this type of conflict.

0
MBOX1

MBOX1

Note:

4-52

Registers

Mailbox One
[7:0]
These are general purpose bits that may be read or
written while SCRIPTS are running. They also may be
read or written by the SCRIPTS processor.
The host and the SCRIPTS processor code could
potentially attempt to access the same mailbox byte at the
same time. Using one mailbox register as a read only and
the other as a write only will prevent this type of conflict.

0
FMT

FMT

Byte Empty in DMA FIFO
[7:0]
These bits identify the bottom bytes in the DMA FIFO that
are empty. Each bit corresponds to a byte lane in the
DMA FIFO. For example, if byte lane three is empty, then
FMT3 will be set. Since the FMT flags indicate the status
of bytes at the bottom of the FIFO, if all FMT bits are set,
the DMA FIFO is empty.

0
FFL

FFL

SCSI Registers

Byte Full in DMA FIFO
[7:0]
These status bits identify the top bytes in the DMA FIFO
that are full. Each bit corresponds to a byte lane in the
DMA FIFO. For example, if byte lane three is full then
FFL3 is set. Since the FFL flags indicate the status of
bytes at the top of the FIFO, if all FFL bits are set, the
DMA FIFO is full.

4-53

DDIR

SIGP

CIO

PCICIE

TEOP

DREQ

DACK

DDIR

Data Transfer Direction
7
This status bit indicates which direction data is being
transferred. When this bit is set, the data is transferred
from the SCSI bus to the host bus. When this bit is clear,
the data is transferred from the host bus to the SCSI bus.

SIGP

Signal Process
6
This bit is a copy of the SIGP bit in the Interrupt Status
Zero (ISTAT0) register (bit= 5). The SIGP bit is used to
signal a running SCRIPTS instruction. When this register
is read, the SIGP bit in the Interrupt Status Zero (ISTAT0)
register is cleared.

CIO

Configured as I/O
5
This bit is defined as the Configuration I/O Enable Status
bit. This read only bit indicates if the chip is currently
enabled as I/O space.

Configured as Memory
4
This bit is defined as the configuration memory enable
status bit. This read only bit indicates if the chip is
currently enabled as memory space.
Note:

PCICIE

Bits 4 and 5 may be set if the chip is mapped in both I/O
and memory space. Also, bits 4 and 5 may be set if the chip
is dual-mapped.
PCI Configuration Into Enable
3
This bit controls the shadowing of the PCI Base Address
Register One (MEMORY), PCI Base Address Register
Two (SCRIPTS RAM), PCI Device ID, and PCI Revision
ID into the Scratch Register A (SCRATCHA), Scratch
Register B (SCRATCHB), and SCRIPTS Fetch Selector
(SFS) registers.
When it is set, the SCRATCHA register contains bits
[31:0] of the Memory Base Address value from the PCI

4-54

Registers

Base Address Register One (MEMORY). This is the
memory mapped operating register base address. Bits
[9:0] will be 0. The SCRATCHB register contains bits
[31:13] of the RAM Base Address value from the PCI
Base Address Register Two (SCRIPTS RAM). This is the
base address for the internal 4 Kbytes RAM. Bits [11:0]
will be 0. Bits [23:16] of SCRIPTS Fetch Selector (SFS)
contain the PCI Revision ID (Rev ID) register value and
bits [15:0] contain the PCI Device ID register value. When
this bit is set, writes to this register have no effect.
When this bit is cleared, the Scratch Register A
(SCRATCHA), Scratch Register B (SCRATCHB), and
SCRIPTS Fetch Selector (SFS) registers return to normal
operation.
Note:

Bit 3 is the only writable bit in this register. All other bits are
read only. When modifying this register, all other bits must
be written to zero. Do not execute a read-modify-write to
this register.

TEOP

SCSI True End of Process
2
This bit indicates the status of the LSI53C875A’s TEOP
signal. The TEOP signal acknowledges the completion of
a transfer through the SCSI portion of the LSI53C875A.
When this bit is set, TEOP is active. When this bit is
clear, TEOP is inactive.

DREQ

Data Request Status
1
This bit indicates the status of the LSI53C875A’s internal
Data Request signal (DREQ). When this bit is set, DREQ
is active. When this bit is clear, DREQ is inactive.

DACK

Data Acknowledge Status
0
This bit indicates the status of the LSI53C875A’s internal
Data Acknowledge signal (DACK/). When this bit is set,
DACK/ is inactive. When this bit is clear, DACK/ is active.

SCSI Registers

4-55

4
V

FLF

CLF

WRIE

Chip Revision Level
[7:4]
These bits identify the chip revision level for software
purposes. It should have the same value as the lower
nibble of the PCI Revision ID (Rev ID) register, at address
0x08 in the configuration space.

FLF

Flush DMA FIFO
3
When this bit is set, data residing in the DMA FIFO is
transferred to memory, starting at the address in the DMA
Next Address 64 (DNAD64) register. The internal
DMAWR signal, controlled by the Chip Test Five
(CTEST5) register, determines the direction of the
transfer. This bit is not self-clearing; clear it once the data
is successfully transferred by the LSI53C875A.
Note:

CLF

Polling of FIFO flags is allowed during flush operations.
Clear DMA FIFO
2
When this bit is set, all data pointers for the DMA FIFO
are cleared. Any data in the FIFO is lost. After the
LSI53C875A successfully clears the appropriate FIFO
pointers and registers, this bit automatically clears.

Note:

This bit does not clear the data visible at the bottom of the
FIFO.
Fetch Pin Mode
1
When set, this bit causes the FETCH/ pin to deassert
during indirect and table indirect read operations.
FETCH/ is only active during the opcode portion of an
instruction fetch. This allows the storage of SCRIPTS in
a PROM while data tables are stored in RAM.
If this bit is not set, FETCH/ is asserted for all bus cycles
during instruction fetches.

4-56

Registers

WRIE

Write and Invalidate Enable
0
This bit, when set, causes the issuing of Write and
Invalidate commands on the PCI bus whenever legal.
The Write and Invalidate Enable bit in the PCI
Configuration Command register must also be set in
order for the chip to generate Write and Invalidate
commands.

Registers: 0x1C–0x1F
Temporary (TEMP)
Read/Write
31

0
TEMP

TEMP

Temporary
[31:0]
This 32-bit register stores the Return instruction address
pointer from the Call instruction. The address pointer
stored in this register is loaded into the DMA SCRIPTS
Pointer (DSP) register when a Return instruction is
executed. This address points to the next instruction to
execute. Do not write to this register while the
LSI53C875A is executing SCRIPTS.
During any Memory-to-Memory Move operation, the
contents of this register are preserved. The power-up
value of this register is indeterminate.

0
BO

SCSI Registers

Byte Offset Counter
[7:0]
These bits, along with bits [1:0] in the Chip Test Five
(CTEST5) register, indicate the amount of data
transferred between the SCSI core and the DMA core. It
is used to determine the number of bytes in the DMA
FIFO when an interrupt occurs. These bits are unstable

4-57

while data is being transferred between the two cores.
Once the chip has stopped transferring data, these bits
are stable.
The DMA FIFO (DFIFO) register counts the number of
bytes transferred between the DMA core and the SCSI
core. The DMA Byte Counter (DBC) register counts the
number of bytes transferred across the host bus. The
difference between these two counters represents the
number of bytes remaining in the DMA FIFO.
The following steps determine how many bytes are left in
the DMA FIFO when an error occurs, regardless of the
transfer direction:
If the DFS bit (bit 5, Chip Test Five (CTEST5)) is set:
1.

Subtract the ten least significant bits of the DMA
Byte Counter (DBC) register from the 10-bit value of
the DFBOC. The DFBOC consists of the Chip Test
Five (CTEST5) register, bits 1 and 0 and the DMA
FIFO (DFIFO) register, bits [7:0].

AND the result with 0x3FF for a byte count between
zero and 944.

If the DFS bit (bit 5, Chip Test Five (CTEST5)) is cleared:

Note:

4-58

Registers

Subtract the seven least significant bits of the DMA
Byte Counter (DBC) register from the seven bit value
of the DFBOC which is made up of the DMA FIFO
(DFIFO) register, bits [6:0].

AND the result with 0x7F for a byte count between
zero and 112.

If trying to calculate the total number of bytes in both the
DMA FIFO and SCSI Logic, see Section 2.2.12.1 “Data
Paths” in Chapter 2, “Functional Description.”

BDIS

FBL3

ZSD

SRTM

MPEE

0
FBL[2:0]

BDIS

Burst Disable
7
When set, this bit causes the LSI53C875A to perform
back-to-back cycles for all transfers. When this bit is
cleared, back-to-back transfers for opcode fetches and
burst transfers for data moves are performed.

FBL3

FIFO Byte Control
6
This bit is used with FBL[2:0]. See Bits [2:0] description
in this register.

ZSD

SCSI Data High Impedance
5
Setting this bit causes the LSI53C875A to place the SCSI
data bus SD[15:0] and the parity lines SDP[1:0] in a high
impedance state. In order to transfer data on the SCSI
bus, clear this bit.

SRTM

Shadow Register Test Mode
4
Setting this bit allows access to the shadow registers
used by Memory-to-Memory Move operations. When this
bit is set, register accesses to the Temporary (TEMP) and
Data Structure Address (DSA) registers are directed to
the shadow copies STEMP (Shadow TEMP) and SDSA
(Shadow DSA). The registers are shadowed to prevent
them from being overwritten during a Memory-to-Memory
Move operation. The DSA and TEMP registers contain
the base address used for table indirect calculations, and
the address pointer for a call or return instruction,
respectively. This bit is intended for manufacturing
diagnostics only and should not be set during normal
operations.

MPEE

Master Parity Error Enable
3
Setting this bit enables parity checking during master
data phases. A parity error during a bus master read is
detected by the LSI53C875A. A parity error during a bus
master write is detected by the target, and the

SCSI Registers

4-59

LSI53C875A is informed of the error by the PERR/ pin
being asserted by the target. When this bit is cleared, the
LSI53C875A does not interrupt if a master parity error
occurs. This bit is cleared at power-up.
FBL[2:0]

FIFO Byte Control

[2:0]

FBL3

FBL2

FBL1

FBL0

DMA FIFO
Byte Lane

Disabled

These bits steer the contents of the Chip Test Six
(CTEST6) register to the appropriate byte lane of the
64-bit DMA FIFO. If the FBL3 bit is set, then FBL2
through FBL0 determine which of eight byte lanes can be
read or written. When cleared, the byte lane read or
written is determined by the current contents of the DMA
Next Address (DNAD) and DMA Byte Counter (DBC)
registers. Each of the eight bytes that make up the 64-bit
DMA FIFO is accessed by writing these bits to the proper
value. For normal operation, FBL3 must equal zero.

ADCK

BBCK

DFS

MASR

DDIR

BL2

ADCK

4-60

Registers

0
BO[9:8]

Clock Address Incrementor
7
Setting this bit increments the address pointer contained
in the DMA Next Address (DNAD) register. The DNAD
register is incremented based on the DNAD contents and

the current DBC value. This bit automatically clears itself
after incrementing the DNAD register.
BBCK

Clock Byte Counter
6
Setting this bit decrements the byte count contained in
the 24-bit DBC register. It is decremented based on the
DMA Byte Counter (DBC) contents and the current DMA
Next Address (DNAD) value. This bit automatically clears
itself after decrementing the DBC register.

DFS

DMA FIFO Size
5
This bit controls the size of the DMA FIFO. When clear,
the DMA FIFO appears as only 112 bytes deep. When
set, the DMA FIFO size increases to 944 bytes. Using an
112-byte FIFO allows software written for other
LSI53C8XX family chips to properly calculate the number
of bytes residing in the chip after a target disconnect. The
default value of this bit is zero.

MASR

Master Control for Set or Reset Pulses
4
This bit controls the operation of bit 3. When this bit is
set, bit 3 asserts the corresponding signals. When this bit
is cleared, bit 3 deasserts the corresponding signals. Do
not change this bit and bit 3 in the same write cycle.

DDIR

DMA Direction
3
Setting this bit either asserts or deasserts the internal
DMA Write (DMAWR) direction signal depending on the
current status of the MASR bit in this register. Asserting
the internal DMA write signal indicates that data is
transferred from the SCSI bus to the host bus.
Deasserting the internal DMA write signal transfers data
from the host bus to the SCSI bus.

BL2

Burst Length Bit 2
2
This bit works with bits 6 and 7 (BL[1:0]) in the DMA
Mode (DMODE), 0x38 register to determine the burst
length. For complete definitions of this field, refer to the
descriptions of DMODE bits 6 and 7. This bit is disabled
if a 112-byte FIFO is selected by clearing the DMA FIFO
size bit.

SCSI Registers

4-61

BO[9:8]

DMA FIFO Byte Offset Counter, Bits [9:8]
[1:0]
These are the upper two bits of the DFBOC. The DFBOC
consists of these bits, and the DMA FIFO (DFIFO)
register, bits [7:0].

0
DF

DMA FIFO
[7:0]
Writing to this register writes data to the appropriate byte
lane of the DMA FIFO as determined by the FBL bits in
the Chip Test Four (CTEST4) register. Reading this
register unloads data from the appropriate byte lane of
the DMA FIFO as determined by the FBL bits in the
CTEST4 register. Data written to the FIFO is loaded into
the top of the FIFO. Data read out of the FIFO is taken
from the bottom. To prevent DMA data from being
corrupted, this register should not be accessed before
starting or restarting SCRIPTS operation. Write this
register only when testing the DMA FIFO using the
CTEST4 register. Writing to this register while the test
mode is not enabled produces unexpected results.

Registers: 0x24–0x26
DMA Byte Counter (DBC)
Read/Write
23

0
DBC

DBC

4-62

Registers

DMA Byte Counter
[23:0]
This 24-bit register determines the number of bytes
transferred in a Block Move instruction. While sending
data to the SCSI bus, the counter is decremented as data
is moved into the DMA FIFO from memory. While
receiving data from the SCSI bus, the counter is
decremented as data is written to memory from the

LSI53C875A. The DBC counter is decremented each
time data is transferred on the PCI bus. It is decremented
by an amount equal to the number of bytes that are
transferred.
The maximum number of bytes that can be transferred in
any one Block Move command is 16,777,215 bytes. The
maximum value that can be loaded into the DMA Byte
Counter (DBC) register is 0xFFFFFF. If the instruction is
a Block Move and a value of 0x000000 is loaded into the
DBC register, an illegal instruction interrupt occurs if the
LSI53C875A is not in target mode, Command phase.
The DBC register is also used to hold the least significant
24 bits of the first Dword of a SCRIPTS fetch, and to hold
the offset value during table indirect I/O SCRIPTS. For a
complete description see Chapter 5, “SCSI SCRIPTS
Instruction Set”. The power-up value of this register is
indeterminate.
See Section 5.3.1, “First Dword,” for register detail.

0
DCMD

DCMD

DMA Command
[7:0]
This 8-bit register determines the instruction for the
LSI53C875A to execute. This register has a different
format for each instruction.
See Section 5.3.1, “First Dword,” for register detail.

SCSI Registers

4-63

Registers: 0x28–0x2B
DMA Next Address (DNAD)
Read/Write
31

0
DNAD

DNAD

DMA Next Address
[31:0]
This 32-bit register contains the general purpose address
pointer. At the start of some SCRIPTS operations, its
value is copied from the DMA SCRIPTS Pointer Save
(DSPS) register. Its value may not be valid except in
certain abort conditions. The default value of this register
is zero.

Registers: 0x2C–0x2F
DMA SCRIPTS Pointer (DSP)
Read/Write
31

0
DSP

DSP

DMA SCRIPTS Pointer
[31:0]
To execute SCSI SCRIPTS, the address of the first
SCRIPTS instruction must be written to this register. In
normal SCRIPTS operation, once the starting address of
the SCRIPT is written to this register, SCRIPTS are
automatically fetched and executed until an interrupt
condition occurs.
In single step mode, there is a single step interrupt after
each instruction is executed. The DMA SCRIPTS Pointer
(DSP) register does not need to be written with the next
address, but the Start DMA bit (bit 2, DMA Control
(DCNTL) register) must be set each time the step
interrupt occurs to fetch and execute the next SCRIPTS
command. When writing this register eight bits at a time,
writing the upper eight bits begins execution of SCSI=
SCRIPTS. The default value of this register is zero.
See Section 5.4.2, “Second Dword,” for register detail.

4-64

Registers

Registers: 0x30–0x33
DMA SCRIPTS Pointer Save (DSPS)
Read/Write
31

0
DSPS

DSPS

DMA SCRIPTS Pointer Save
[31:0]
This register contains the second Dword of a SCRIPTS
instruction. It is overwritten each time a SCRIPTS
instruction is fetched. When a SCRIPTS interrupt
instruction is executed, this register holds the interrupt
vector. The power-up value of this register is
indeterminate.

Registers: 0x34–0x37
Scratch Register A (SCRATCHA)
Read/Write
31

0
SCRATCHA

SCRATCHA

Scratch Register A
[31:0]
This is a general purpose, user-definable scratch pad
register. Apart from CPU access, only Register
Read/Write and Memory Moves into the SCRATCH
register alter its contents. The power-up value of this
register is indeterminate.
A special mode of this register is enabled by setting the
PCI Configuration Into Enable bit in the Chip Test Two
(CTEST2) register. If this bit is set, the SCRATCH A
register returns bits [31:10] of the Memory Mapped
Operating register PCI base address (Base Address Register One (MEMORY)) in bits [31:10] of the Scratch Register A (SCRATCHA) when read. Bits [9:0] of SCRATCH
A will always return zero in this mode. Writes to the
SCRATCH A register are unaffected. Clearing the PCI
Configuration Into Enable bit causes the SCRATCH A
register to return to normal operation.

SCSI Registers

4-65

6
BL[1:0]

BL[1:0]

SIOM

DIOM

ERL

ERMP

BOF

MAN

Burst Length
[7:6]
These bits control the maximum number of Dwords
transferred per bus ownership, regardless of whether the
transfers are back-to-back, burst, or a combination of
both. The LSI53C875A asserts the Bus Request (REQ/)
output when the DMA FIFO can accommodate a transfer
of at least one burst threshold of data. Bus Request
(REQ/) is also asserted during start-of-transfer and
end-of-transfer cleanup and alignment, even if less than
a full burst of transfers is performed. The LSI53C875A
inserts a “fairness delay” of four CLKs between burst
transfers (as set in BL[2:0]) during normal operation. The
fairness delay is not inserted during PCI retry cycles. This
gives the CPU and other bus master devices the
opportunity to access the PCI bus between bursts.
The LSI53C875A will only support burst thresholds of up
to 16 Dwords in the small FIFO mode. Setting the burst
threshold to higher than 16 Dwords in the small FIFO
mode will yield unexpected results in burst lengths. The
big FIFO mode is activated by setting bit 5 of the Chip
Test Five (CTEST5) register. In the big FIFO mode, the
LSI53C875A will support burst thresholds of up to
128 Dwords.

4-66

Registers

BL2
(CTEST5 bit 2)

BL1

BL0

Burst Length
Transfers

Dwords

321

641

1281

Reserved

1. The 944-byte FIFO must be enabled for these burst sizes.

SIOM

Source I/O Memory Enable
5
This bit is defined as an I/O Memory Enable bit for the
source address of a Memory Move or Block Move
Command. If this bit is set, then the source address is in
I/O space; and if cleared, then the source address is in
memory space.
This function is useful for register-to-memory operations
using the Memory Move instruction when the
LSI53C875A is I/O mapped. Bits 4 and 5 of the Chip Test
Two (CTEST2) register are used to determine the
configuration status of the LSI53C875A.

DIOM

Destination I/O Memory Enable
4
This bit is defined as an I/O Memory Enable bit for the
destination address of a Memory Move or Block Move
Command. If this bit is set, then the destination address
is in I/O space; and if cleared, then the destination
address is in memory space.
This function is useful for memory-to-register operations
using the Memory Move instruction when the
LSI53C875A is I/O mapped. Bits 4 and 5 of the Chip Test
Two (CTEST2) register are used to determine the
configuration status of the LSI53C875A.

ERL

SCSI Registers

Enable Read Line
3
This bit enables a PCI Read Line command. If this bit is
set and the chip is about to execute a read cycle other
than an opcode fetch, then the command is 0b1110.

4-67

4-68

ERMP

Enable Read Multiple
2
If this bit is set and cache mode is enabled, a Read
Multiple command is used on all read cycles when it is
legal.

BOF

Burst Opcode Fetch Enable
1
Setting this bit causes the LSI53C875A to fetch
instructions in burst mode. Specifically, the chip bursts in
the first two Dwords of all instructions using a single bus
ownership. If the instruction is a Memory-to-Memory
Move type, the third Dword is accessed in a subsequent
bus ownership. If the instruction is an indirect type, the
additional Dword is accessed in a subsequent bus
ownership. If the instruction is a table indirect block move
type, the chip accesses the remaining two Dwords in a
subsequent bus ownership, thereby fetching the four
Dwords required in two bursts of two Dwords each. If
prefetch is enabled, this bit has no effect. This bit also
has no effect on fetches out of SCRIPTS RAM.

MAN

Manual Start Mode
0
Setting this bit prevents the LSI53C875A from
automatically fetching and executing SCSI SCRIPTS
when the DMA SCRIPTS Pointer (DSP) register is
written. When this bit is set, the Start DMA bit in the DMA
Control (DCNTL) register must be set to begin SCRIPTS
execution. Clearing this bit causes the LSI53C875A to
automatically begin fetching and executing SCSI
SCRIPTS when the DSP register is written. This bit
normally is not used for SCSI SCRIPTS operations.

Registers

MDPE

ABRT

SSI

SIR

IID

Reserved

MDPE

Master Data Parity Error

Bus Fault

ABRT

Aborted

SSI

Single Step Interrupt

SIR

SCRIPTS Interrupt Instruction Received

Reserved

IID

Illegal Instruction Detected

This register contains the interrupt mask bits corresponding to the
interrupting conditions described in the DMA Status (DSTAT) register. An
interrupt is masked by clearing the appropriate mask bit. Masking an
interrupt prevents IRQ/ from being asserted for the corresponding
interrupt, but the status bit is still set in the DSTAT register. Masking an
interrupt does not prevent setting the Interrupt Status Zero (ISTAT0) DIP.
All DMA interrupts are considered fatal, therefore SCRIPTS stops
running when this condition occurs, whether or not the interrupt is
masked. Setting a mask bit enables the assertion of IRQ/ for the
corresponding interrupt. (A masked nonfatal interrupt does not prevent
unmasked or fatal interrupts from getting through; interrupt stacking
begins when either the Interrupt Status Zero (ISTAT0) SIP or DIP bit is
set.)
The IRQ/ output is latched. Once asserted, it will remain asserted until
the interrupt is cleared by reading the appropriate status register.
Masking an interrupt after the IRQ/ output is asserted does not cause
deassertion of IRQ/.

SCSI Registers

4-69

For more information on interrupts, see Chapter 2, “Functional
Description”.

0
SBR

SBR

Scratch Byte Register
[7:0]
This is a general purpose register. Apart from CPU
access, only register Read/Write and Memory Moves into
this register alter its contents. The default value of this
register is zero. This register is called the DMA Watchdog
Timer on previous LSI53C8XX family products.

4-70

CLSE

PFF

PFEN

SSM

IRQM

STD

IRQD

COM

CLSE

Cache Line Size Enable
7
Setting this bit enables the LSI53C875A to sense and
react to cache line boundaries set up by the DMA Mode
(DMODE) or PCI Cache Line Size register, whichever
contains the smaller value. Clearing this bit disables the
cache line size logic and the LSI53C875A monitors the
cache line size using the DMODE register.

PFF

Prefetch Flush
Setting this bit causes the prefetch unit to flush its
contents. The bit clears after the flush is complete.

PFEN

Prefetch Enable
5
Setting this bit enables an 8-Dword SCRIPTS instruction
prefetch unit. The prefetch unit, when enabled, will fetch
8 Dwords of instructions and instruction operands in
bursts of 4 or 8 Dwords. Prefetching instructions allows

Registers

the LSI53C875A to make more efficient use of the
system PCI bus, thus improving overall system
performance. The unit will flush whenever the PFF bit is
set, as well as on all transfer control instructions when
the transfer conditions are met, on every write to the
DMA SCRIPTS Pointer (DSP), on every regular MMOV
instruction, and when any interrupt is generated. The unit
automatically determines the maximum burst size that it
is capable of performing based on the burst length as
determined by the values in the DMA Mode (DMODE)
register. If the burst threshold is set to 8 Dwords the
prefetch unit will fetch instructions in two bursts of
4 Dwords. If the burst threshold is set to 16 Dwords or
greater the prefetch unit will fetch instructions in one burst
of 8 Dwords. Burst thresholds of less than 8 Dwords will
cause the prefetch unit to be disabled. PCI Cache
commands (Read Line and Read Multiple) will be issued
appropriately if PCI caching is enabled. Prefetching from
SCRIPTS RAM is not supported and is unnecessary due
to the speed of the fetches. When fetching from
SCRIPTS RAM the setting of this bit will have no effect
on the fetch mechanism from SCRIPTS RAM.
SSM

Single Step Mode
4
Setting this bit causes the LSI53C875A to stop after
executing each SCRIPTS instruction, and generate a
single step interrupt. When this bit is cleared the
LSI53C875A does not stop after each instruction. It
continues fetching and executing instructions until an
interrupt condition occurs. For normal SCSI SCRIPTS
operation, keep this bit clear. To restart the LSI53C875A
after it generates a SCRIPTS Step interrupt, read the
Interrupt Status Zero (ISTAT0), Interrupt Status One
(ISTAT1) and DMA Status (DSTAT) registers to recognize
and clear the interrupt. Then set the START DMA bit in
this register.

IRQM

IRQ Mode
3
When set, this bit enables a totem pole driver for the IRQ/
pin. When cleared, this bit enables an open drain driver
for the IRQ/ pin with an internal weak pull-up. The bit
should remain cleared to retain full PCI compliance.

SCSI Registers

4-71

STD

Start DMA Operation
2
The LSI53C875A fetches a SCSI SCRIPTS instruction
from the address contained in the DMA SCRIPTS Pointer
(DSP) register when this bit is set. This bit is required if
the LSI53C875A is in one of the following modes:

• Manual start mode – Bit 0 in the DMA Mode
(DMODE) register is set

• Single step mode – Bit 4 in the DMA Control (DCNTL)
register is set
When the LSI53C875A is executing SCRIPTS in manual
start mode, the Start DMA bit must be set to start
instruction fetches, but need not be set again until an
interrupt occurs. When the LSI53C875A is in single step
mode, set the Start DMA bit to restart execution of
SCRIPTS after a single step interrupt.
IRQD

IRQ Disable
1
Setting this bit disables the IRQ pin. Clearing the bit
enables normal operation. As with any other register
other than Interrupt Status Zero (ISTAT0) and Interrupt
Status One (ISTAT1), this register cannot be accessed
except by a SCRIPTS instruction during SCRIPTS
execution. For more information on the use of this bit in
interrupt handling, see Chapter 2, “Functional
Description.”

COM

LSI53C700 Compatibility
0
When the COM bit is cleared, the LSI53C875A behaves
in a manner compatible with the LSI53C700;
selection/reselection IDs are stored in both the SCSI
Selector ID (SSID) and SCSI First Byte Received (SFBR)
registers. This bit is not affected by a software reset.
If the COM bit is cleared, do not access this register
using SCRIPTS operation as nondeterminate operations
may occur. (This includes SCRIPTS Read/Write
operations and conditional transfer control instructions
that initialize the SFBR register.)
When the COM bit is set, the ID is stored only in the
SSID register, protecting the SFBR from being
overwritten if a selection/reselection occurs during a DMA
register-to-register operation.

4-72

Registers

Registers: 0x3C–0x3F
Adder Sum Output (ADDER)
Read Only
31

0
ADDER

ADDER

Adder Sum Output
[31:0]
This register contains the output of the internal adder,
and is used primarily for test purposes. The power-up
value for this register is indeterminate. It is used to
determine if the correct memory address was calculated
for a relative jump SCRIPTS instruction.

M/A

CMP

SEL

RSL

SGE

UDC

RST

PAR

This register contains the interrupt mask bits corresponding to the
interrupting conditions described in the SCSI Interrupt Status Zero
(SIST0) register. An interrupt is masked by clearing the appropriate mask
bit. For more information on interrupts, see Chapter 2, “Functional
Description.”
M/A

SCSI Registers

SCSI Phase Mismatch - Initiator Mode;
7
SCSI ATN Condition - Target Mode
In the initiator mode, this bit is set when the SCSI phase
asserted by the target and sampled during SREQ/ does
not match the expected phase in the SCSI Output Control
Latch (SOCL) register. This expected phase is
automatically written by SCSI SCRIPTS. In target mode,
this bit is set when the initiator asserts SATN/. See the
Disable Halt on Parity Error or SATN/ Condition bit in the
SCSI Control One (SCNTL1) register for more
information on when this status is actually raised.

4-73

CMP

Function Complete
Indicates full arbitration and selection sequence is
completed.

SEL

Selected
5
Indicates the LSI53C875A is selected by a SCSI initiator
device. Set the Enable Response to Selection bit in the
SCSI Chip ID (SCID) register for this to occur.

RSL

Reselected
4
Indicates the LSI53C875A is reselected by a SCSI target
device. Set the Enable Response to Reselection bit in the
SCSI Chip ID (SCID) register for this to occur.

SGE

SCSI Gross Error
The following conditions are considered SCSI Gross
Errors:

• Data underflow – reading the SCSI FIFO when no
data is present.

• Data overflow – writing to the SCSI FIFO while it is
full.

• Offset underflow – receiving a SACK/ pulse in target
mode before the corresponding SREQ/ is sent.

• Offset overflow – receiving an SREQ/ pulse in the
initiator mode, and exceeding the maximum offset
(defined by the MO[3:0] bits in the SCSI Transfer
(SXFER) register).

• A phase change in the initiator mode, with an
outstanding SREQ/SACK/ offset.

• Residual data in SCSI FIFO – starting a transfer other
than synchronous data receive with data left in the
SCSI synchronous receive FIFO.
UDC

4-74

Registers

Unexpected Disconnect
2
This condition only occurs in the initiator mode. It
happens when the target to which the LSI53C875A is
connected disconnects from the SCSI bus unexpectedly.
See the SCSI Disconnect Unexpected bit in the SCSI
Control Two (SCNTL2) register for more information on
expected versus unexpected disconnects. Any
disconnect in low level mode causes this condition.

RST

SCSI Reset Condition
1
Indicates assertion of the SRST/ signal by the
LSI53C875A or any other SCSI device. This condition is
edge-triggered, so multiple interrupts cannot occur
because of a single SRST/ pulse.

PAR

SCSI Parity Error
0
Indicates detection by the LSI53C875A of a parity error
while receiving or sending SCSI data. See the Disable
Halt on Parity Error or SATN/ Condition bits in the SCSI
Control One (SCNTL1) register for more information on
when this condition is actually raised.

3
R

STO

GEN

HTH

This register contains the interrupt mask bits corresponding to the
interrupting conditions described in the SCSI Interrupt Status One
(SIST1) register. An interrupt is masked by clearing the appropriate mask
bit. For more information on interrupts, refer to Chapter 2, “Functional
Description.”
R

Reserved

STO

Selection or Reselection Time-out
2
The SCSI device which the LSI53C875A is attempting to
select or reselect does not respond within the
programmed time-out period. See the description of the
SCSI Timer Zero (STIME0) register bits [3:0] for more
information on the time-out timer.

GEN

General Purpose Timer Expired
1
The general purpose timer is expired. The time measured
is the time between enabling and disabling of the timer.
See the description of the SCSI Timer One (STIME1)
register, bits [3:0], for more information on the general
purpose timer.

SCSI Registers

[7:3]

4-75

HTH

Handshake-to-Handshake Timer Expired
0
The handshake-to-handshake timer is expired. The time
measured is the SCSI Request-to-Request (target) or
Acknowledge-to-Acknowledge (initiator) period. See the
description of the SCSI Timer Zero (STIME0) register,
bits [7:4], for more information on the handshaketo-handshake timer.

M/A

CMP

SEL

RSL

SGE

UDC

RST

PAR

Reading the SIST0 register returns the status of the various interrupt
conditions, whether they are enabled in the SCSI Interrupt Enable Zero
(SIEN0) register or not. Each bit set indicates occurrence of the
corresponding condition. Reading the SIST0 clears the interrupt status.
Reading this register clears any bits that are set at the time the register
is read, but does not necessarily clear the register because additional
interrupts may be pending (the LSI53C875A stacks interrupts). SCSI
interrupt conditions are individually masked through the SCSI Interrupt
Enable Zero (SIEN0) register.
When performing consecutive 8-bit reads of the DMA Status (DSTAT),
SCSI Interrupt Status Zero (SIST0), and SCSI Interrupt Status One
(SIST1) registers (in any order), insert a delay equivalent to 12 CLK
periods between the reads to ensure the interrupts clear properly. Also,
if reading the registers when both the Interrupt Status Zero (ISTAT0) SIP
and DIP bits may not be set, read the SIST0 and SIST1 registers before
the DSTAT register to avoid missing a SCSI interrupt. For more
information on interrupts, refer to Chapter 2, “Functional Description.”
M/A

4-76

Registers

Initiator Mode: Phase Mismatch; Target Mode:
SATN/ Active
7
In the initiator mode, this bit is set if the SCSI phase
asserted by the target does not match the instruction.
The phase is sampled when SREQ/ is asserted by the

target. In target mode, this bit is set when the SATN/
signal is asserted by the initiator.
CMP

Function Complete
6
This bit is set when an arbitration only or full arbitration
sequence is completed.

SEL

Selected
5
This bit is set when the LSI53C875A is selected by
another SCSI device. The Enable Response to Selection
bit must be set in the SCSI Chip ID (SCID) register (and
the Response ID Zero (RESPID0) and Response ID One
(RESPID1) register must hold the chip’s ID) for the
LSI53C875A to respond to selection attempts.

RSL

Reselected
4
This bit is set when the LSI53C875A is reselected by
another SCSI device. The Enable Response to
Reselection bit must be set in the SCID register (and the
Response ID Zero (RESPID0) and Response ID One
(RESPID1) registers must hold the chip’s ID) for the
LSI53C875A to respond to reselection attempts.

SGE

SCSI Gross Error
3
This bit is set when the LSI53C875A encounters a SCSI
Gross Error Condition. The following conditions can result
in a SCSI Gross Error Condition:

• Data Underflow – reading the SCSI FIFO when no
data is present.

• Data Overflow – writing too many bytes to the SCSI
FIFO, or the synchronous offset causes overwriting
the SCSI FIFO.

• Offset Underflow – the LSI53C875A is operating in
target mode and a SACK/ pulse is received when the
outstanding offset is zero.

• Offset Overflow – the other SCSI device sends a
SREQ/ or SACK/ pulse with data which exceeds the
maximum synchronous offset defined by the SCSI
Transfer (SXFER) register.

• A phase change occurs with an outstanding
synchronous offset when the LSI53C875A is
operating as an initiator.

SCSI Registers

4-77

• Residual data in the synchronous data FIFO – a
transfer other than synchronous data receive is
started with data left in the synchronous data FIFO.
UDC

Unexpected Disconnect
2
This bit is set when the LSI53C875A is operating in the
initiator mode and the target device unexpectedly
disconnects from the SCSI bus. This bit is only valid
when the LSI53C875A operates in the initiator mode.
When the LSI53C875A operates in low level mode, any
disconnect causes an interrupt, even a valid SCSI
disconnect. This bit is also set if a selection time-out
occurs (it may occur before, at the same time, or stacked
after the STO interrupt, since this is not considered an
expected disconnect).

RST

SCSI RST/ Received
1
This bit is set when the LSI53C875A detects an active
SRST/ signal, whether the reset is generated external to
the chip or caused by the Assert RST bit in the SCSI
Control One (SCNTL1) register. This SCSI reset
detection logic is edge-sensitive, so that multiple
interrupts are not generated for a single assertion of the
SRST/ signal.

PAR

Parity Error
0
This bit is set when the LSI53C875A detects a parity
error while receiving SCSI data. The Enable Parity
Checking bit (bit 3 in the SCSI Control Zero (SCNTL0)
register) must be set for this bit to become active. The
LSI53C875A always generates parity when sending SCSI
data.

3
R

STO

GEN

HTH

Reading the SIST1 register returns the status of the various interrupt
conditions, whether they are enabled in the SCSI Interrupt Enable One

4-78

Registers

(SIEN1) register or not. Each bit that is set indicates an occurrence of
the corresponding condition.
Reading the SIST1 clears the interrupt condition.
R

Reserved

[7:3]

STO

Selection or Reselection Time-out
2
The SCSI device which the LSI53C875A is attempting to
select or reselect does not respond within the
programmed time-out period. See the description of the
SCSI Timer Zero (STIME0) register, bits [3:0], for more
information on the time-out timer.

GEN

General Purpose Timer Expired
1
This bit is set when the general purpose timer expires.
The time measured is the time between enabling and
disabling of the timer. See the description of the SCSI
Timer One (STIME1) register, bits [3:0], for more
information on the general purpose timer.

HTH

Handshake-to-Handshake Timer Expired
0
This bit is set when the handshake-to-handshake timer
expires. The time measured is the SCSI Request to
Request (target) or Acknowledge-to-Acknowledge
(initiator) period. See the description of the SCSI Timer
Zero (STIME0) register, bits [7:4], for more information on
the handshake-to-handshake timer.

0
SLPAR

SLPAR

SCSI Registers

SCSI Longitudinal Parity
[7:0]
This register performs a bytewise longitudinal parity
check on all SCSI data received or sent through the SCSI
core. If one of the bytes received or sent (usually the last)
is the set of correct even parity bits, SLPAR should go to
zero (assuming it started at zero). As an example,
suppose that the following three data bytes and one

4-79

check byte are received from the SCSI bus (all signals
are shown active HIGH):
Data Bytes
–

Running SLPAR
00000000

1. 11001100

11001100 (XOR of word 1)

2. 01010101

10011001 (XOR of word 1 and 2)

3. 00001111

10010110 (XOR of word 1, 2 and 3) Even Parity

4. 10010110

00000000

A one in any bit position of the final SLPAR value would
indicate a transmission error.
The SLPAR register is also used to generate the check
bytes for SCSI send operations. If the SLPAR register
contains all zeros prior to sending a block move, it
contains the appropriate check byte at the end of the
block move. This byte must then be sent across the SCSI
bus.
Note:

Writing any value to this register clears it to zero.
The longitudinal parity checks are meant to provide an
added measure of SCSI data integrity and are entirely
optional. This register does not latch SCSI
selection/reselection IDs under any circumstances. The
default value of this register is zero.
The longitudinal parity function normally operates as a
byte function. During 16-bit transfers, the high and low
bytes are XORed together and then XORed into the
current longitudinal parity value. By setting the SLPMD bit
in the SCSI Control Two (SCNTL2) register, the
longitudinal parity function is made to operate as a
word-wide function. During 16-bit transfers, the high byte
of the SCSI bus is XORed with the high byte of the
current longitudinal parity value, and the low byte of the
SCSI bus is XORed with the low byte of the current
longitudinal parity value. In this mode, the 16-bit
longitudinal parity value is accessed a byte at a time
through the SCSI Longitudinal Parity (SLPAR) register.

4-80

Registers

Which byte is accessed is controlled by the SLPHBEN bit
in the SCSI Control Two (SCNTL2) register.

0
SWIDE

SWIDE

SCSI Wide Residue
[7:0]
After a wide SCSI data receive operation, this register
contains a residual data byte if the last byte received was
never sent across the DMA bus. It represents either the
first data byte of a subsequent data transfer, or it is a
residue byte which should be cleared when an Ignore
Wide Residue message is received. It may also be an
overrun data byte. The power-up value of this register is
indeterminate.

4
TYP

TYP

DWR

DRD

PSCPT

SCPTS

Chip Type
[7:4]
These bits identify the chip type for software purposes.
Note:

These bits no longer identify an 8XX device. These bits
have been set to 0xF to indicate that the device should be
uniquely identified by setting the PCI Configuration Enable
bit in the Chip Test Two (CTEST2) register and using the
PCI Revision ID and PCI Device ID which will be shadowed
in the SCRIPTS Fetch Selector (SFS) register. Any devices
that contain the value 0xF in this register should use this
mechanism to uniquely identify the device.

SCSI Registers

4-81

DWR

Data Write
3
This bit is used to define if a data write is considered to
be a local memory access.

DRD

Data Read
2
This bit is used to define if a data read is considered to
be a local memory access.

PSCPT

Pointer SCRIPTS
1
This bit is used to define if a pointer to a SCRIPTS
indirect or table indirect fetch is considered to be a local
memory access.

SCPTS

SCRIPTS
This bit is used to define if a SCRIPTS fetch is
considered to be a local memory access.

LEDC

GPIO
0

0
GPIO

This register is used to determine if the pins controlled by the General
Purpose (GPREG0) register are inputs or outputs. Bits [4:0] in GPCNTL0
correspond to bits [4:0] in the GPREG0 register. When the bits are
enabled as inputs, internal pull-downs are enabled for GPIO[4:2] and
internal pull-ups are enabled for GPIO[1:0].
The data written to each bit of the GPREG0 register is output to the
appropriate GPIO pin if it is set to the output mode in the GPCNTL0
register.

4-82

Master Enable
7
The internal bus master signal is presented on GPIO1 if
this bit is set, regardless of the state of bit 1 (GPIO1).

Fetch Enable
6
The internal opcode fetch signal is presented on GPIO0
if this bit is set, regardless of the state of bit 0 (GPIO0).

Registers

LEDC

LED_CNTL
5
The internal connected signal (bit 3 of the Interrupt Status
Zero (ISTAT0) register) will be presented on GPIO0 if this
bit is set and bit 6 of GPCNTL0 is cleared and the chip
is not in progress of performing an EEPROM
autodownload regardless of the state of bit 0 (GPIO0).
This provides a hardware solution to driving a SCSI
activity LED in many implementations of LSI Logic SCSI
chips.

GPIO

GPIO Enable
[4:2]
General purpose control, corresponding to bits [4:2] in
the GPREG0 register and pins GPIO[4:2]. GPIO4 powers
up as a general purpose output, and GPIO[3:2] power-up
as general purpose inputs.

GPIO

GPIO Enable
[1:0]
These bits power-up set, causing the GPIO1 and GPIO0
pins to become inputs. Clearing these bits causes
GPIO[1:0] to become outputs.

HTH[3:0]
0

HTH[3:0]

SCSI Registers

SEL[3:0]
0

Handshake-to-Handshake Timer Period
[7:4]
These bits select the handshake-to-handshake time-out
period, the maximum time between SCSI handshakes
(SREQ/ to SREQ/ in target mode, or SACK/ to SACK/ in
initiator mode). When this timing is exceeded, an interrupt
is generated and the HTH bit in the SCSI Interrupt Status
One (SIST1) register is set. The following table contains
time-out periods for the Handshake-to-Handshake Timer,
the Selection/Reselection Timer (bits [3:0]), and the
General Purpose Timer (SCSI Timer One (STIME1) bits
[3:0]). For a more detailed explanation of interrupts, refer
to Chapter 2, “Functional Description.”

4-83

HTH [3:0]
SEL [3:0]
GEN [3:0]

Minimum Time-out
(80 MHz Clock) With
Scale Factor Bit Cleared1

Minimum Time-out
(80 MHz Clock) With
Scale Factor Bit Set

0000

Disabled

0001

100 µs

1.6 ms

0010

200 µs

3.2 ms

0011

400 µs

6.4 ms

0100

800 µs

12.8 ms

0101

1.6 ms

25.6 ms

0110

3.2 ms

51.2 ms

0111

6.4 ms

102.4 ms

1000

12.8 ms

204.8 ms

1001

25.6 ms

409.6 ms

1010

51.2 ms

819.2 ms

1011

102.4 ms

1.6 s

1100

204.8 ms

3.2 s

1101

409.6 ms

6.4 s

1110

819.2 ms

12.8 s

1111

1.6 + s

25.6 s

1. These values are correct if the CCF bits in the SCSI Control Three (SCNTL3)
register are set according to the valid combinations in the bit description.

SEL[3:0]

4-84

Registers

Selection Time-Out
[3:0]
These bits select the SCSI selection/reselection time-out
period. When this timing (plus the 200 µs selection abort
time) is exceeded, the STO bit in the SCSI Interrupt
Status One (SIST1) register is set. For a more detailed
explanation of interrupts, refer to Chapter 2, “Functional
Description.”

HTHBA

GENSF

HTHSF

0
GEN[3:0]

Reserved

HTHBA

Handshake-to-Handshake Timer Bus Activity
Enable
6
Setting this bit causes this timer to begin testing for SCSI
REQ/, ACK/ activity as soon as SBSY/ is asserted,
regardless of the agents participating in the transfer.

GENSF

General Purpose Timer Scale Factor
5
Setting this bit causes this timer to shift by a factor of 16.
Refer to the SCSI Timer Zero (STIME0) register
description for details.

HTHSF

Handshake-to-Handshake Timer Scale Factor
4
Setting this bit causes this timer to shift by a factor of 16.
Refer to the SCSI Timer Zero (STIME0) register
description for details.

GEN[3:0]

General Purpose Timer Period
[3:0]
These bits select the period of the general purpose timer.
The time measured is the time between enabling and
disabling of the timer. When this timing is exceeded, the
GEN bit in the SCSI Interrupt Status One (SIST1) register
is set. Refer to the table under SCSI Timer Zero
(STIME0), bits [3:0], for the available time-out periods.

Note:

To reset a timer before it expires and obtain repeatable
delays, the time value must be written to zero first, and then
written back to the desired value. This is also required
when changing from one time value to another.

SCSI Registers

4-85

0
RESPID0

RESPIO0

Response ID Zero
[7:0]
RESPID0 and Response ID One (RESPID1) contain the
selection or reselection IDs. In other words, these two
8-bit registers contain the ID that the chip responds to on
the SCSI bus. Each bit represents one possible ID with
the most significant bit of RESPID1 representing ID 15
and the least significant bit of RESPID0 representing
ID 0. The SCSI Chip ID (SCID) register still contains the
chip ID used during arbitration. The chip can respond to
more than one ID because more than one bit can be set
in the RESPID1 and RESPID0 registers. However, the
chip can arbitrate with only one ID value in the SCID
register.

0
RESPID1

RESPID1

4-86

Registers

Response ID One
[7:0]
Response ID Zero (RESPID0) and RESPID1 contain the
selection or reselection IDs. In other words, these two
8-bit registers contain the ID that the chip responds to on
the SCSI bus. Each bit represents one possible ID with
the most significant bit of RESPID1 representing ID 15
and the least significant bit of RESPID0 representing
ID 0. The SCSI Chip ID (SCID) register still contains the
chip ID used during arbitration. The chip can respond to
more than one ID because more than one bit can be set
in the RESPID1 and RESPID0 registers. However, the

chip can arbitrate with only one ID value in the SCID
register.

4
SSAID

SLT

ART

SOZ

SOM

SSAID

SCSI Selected As ID
[7:4]
These bits contain the encoded value of the SCSI ID that
the LSI53C875A is selected during a SCSI selection
phase. These bits work in conjunction with the Response
ID Zero (RESPID0) and Response ID One (RESPID1)
registers, which contain the allowable IDs that the
LSI53C875A can respond to. During a SCSI selection
phase, when a valid ID is put on the bus, and the
LSI53C875A responds to that ID, the ID that the chip was
selected as will be written into the SSAID[3:0] bits.

SLT

Selection Response Logic Test
3
This bit is set when the LSI53C875A is ready to be
selected or reselected. This does not take into account
the bus settle delay of 400 ns. This bit is used for
functional test and fault purposes.

ART

Arbitration Priority Encoder Test
2
This bit is always set when the LSI53C875A exhibits the
highest priority ID asserted on the SCSI bus during
arbitration. It is primarily used for chip level testing, but it
may be used during low level mode operation to
determine if the LSI53C875A won arbitration.

SOZ

SCSI Synchronous Offset Zero
1
This bit indicates that the current synchronous SREQ/,
SACK/ offset is zero. This bit is not latched and may
change at any time. It is used in low level synchronous
SCSI operations. When this bit is set, the LSI53C875A
functioning as an initiator, is waiting for the target to
request data transfers. If the LSI53C875A is a target,
then the initiator has sent the offset number of
acknowledges.

SCSI Registers

4-87

SOM

SCSI Synchronous Offset Maximum
0
This bit indicates that the current synchronous SREQ/,
SACK/ offset is the maximum specified by bits [3:0] in the
SCSI Transfer (SXFER) register. This bit is not latched
and may change at any time. It is used in low level
synchronous SCSI operations. When this bit is set, the
LSI53C875A, as a target, is waiting for the initiator to
acknowledge the data transfers. If the LSI53C875A is an
initiator, then the target has sent the offset number of
requests.

4-88

SCLK

ISO

4
R

QEN

QSEL

0
R

SCLK

SCSI Clock
7
When set, this bit disables the external SCLK (SCSI
Clock) pin, and the chip uses the PCI clock as the
internal SCSI clock. When set, it will also select the PCI
clock as the internal SCSI clock if the internal clock
quadrupler is enabled and selected.

ISO

SCSI Isolation Mode
6
This bit allows the LSI53C875A to put the SCSI
bidirectional and input pins into a low power mode when
the SCSI bus is not in use. When this bit is set, the SCSI
bus inputs are logically isolated from the SCSI bus.

Reserved

QEN

SCLK Quadrupler Enable
3
This bit, when set, powers up the internal clock
quadrupler circuit, which quadruples the SCLK. A 40
MHz clock is quadrupled to an internal 160 MHz SCSI
clock, as required for Ultra SCSI operation. The output
from a 20 MHz SCLK is 80 MHz. When cleared, this bit
powers down the internal quadrupler circuit.

Registers

[5:4]

QSEL

SCLK Quadrupler Select
2
This bit, when set, selects the output of the internal clock
quadrupler for use as the internal SCSI clock. When
cleared, this bit selects the clock presented on SCLK for
use as the internal SCSI clock.

Reserved

[1:0]

SCE

ROF

SLB

SZM

AWS

EXT

LOW

SCE

SCSI Control Enable
7
Setting this bit allows assertion of all SCSI control and
data lines through the SCSI Output Control Latch (SOCL)
and SCSI Output Data Latch (SODL) registers regardless
of whether the LSI53C875A is configured as a target or
initiator.
Note:

Do not set this bit during normal operation, since it could
cause contention on the SCSI bus. It is included for
diagnostic purposes only.

ROF

Reset SCSI Offset
6
Setting this bit clears any outstanding synchronous
SREQ/SACK offset. Set this bit if a SCSI gross error
condition occurs and to clear the offset when a
synchronous transfer does not complete successfully.
The bit automatically clears itself after resetting the
synchronous offset.

Reserved
This bit must be cleared.

SLB

SCSI Loopback Mode
4
Setting this bit allows the LSI53C875A to perform SCSI
loopback diagnostics. That is, it enables the SCSI core to
simultaneously perform as both the initiator and the
target.

SCSI Registers

4-89

SZM

SCSI High Impedance Mode
3
Setting this bit places all the open drain 48 mA SCSI
drivers into a high impedance state. This is to allow
internal loopback mode operation without affecting the
SCSI bus.

AWS

Always Wide SCSI
2
When this bit is set, all SCSI information transfers are
done in 16-bit wide mode. This includes data, message,
command, status and reserved phases. Normally,
deassert this bit since 16-bit wide message, command,
and status phases are not supported by the SCSI
specifications.

EXT

Extend SREQ/SACK/ Filtering
1
LSI Logic TolerANT SCSI receiver technology includes a
special digital filter on the SREQ/ and SACK/ pins which
causes the disregarding of glitches on deasserting
edges. Setting this bit increases the filtering period from
30 ns to 60 ns on the deasserting edge of the SREQ/ and
SACK/ signals.
Note:

LOW

Note:

4-90

Registers

Never set this bit during fast SCSI (greater than 5 Mbyte
transfers per second) operations, because a valid assertion
could be treated as a glitch.
SCSI Low level Mode
0
Setting this bit places the LSI53C875A in the low level
mode. In this mode, no DMA operations occur, and no
SCRIPTS execute. Arbitration and selection may be
performed by setting the start sequence bit as described
in the SCSI Control Zero (SCNTL0) register. SCSI bus
transfers are performed by manually asserting and polling
SCSI signals. Clearing this bit allows instructions to be
executed in SCSI SCRIPTS mode.
It is not necessary to set this bit for access to the SCSI
bit-level registers SCSI Output Data Latch (SODL), SCSI
Bus Control Lines (SBCL), and input registers.

STR

HSC

DSI

S16

TTM

CSF

STW

TolerANT Enable
7
Setting this bit enables the active negation portion of
LSI Logic TolerANT technology. Active negation causes
the SCSI Request, Acknowledge, Data, and Parity
signals to be actively deasserted, instead of relying on
external pull-ups, when the LSI53C875A is driving these
signals. Active deassertion of these signals occurs only
when the LSI53C875A is in an information transfer
phase. When operating in a differential environment or at
fast SCSI timings, TolerANT Active negation should be
enabled to improve setup and deassertion times. Active
negation is disabled after reset or when this bit is cleared.
For more information on LSI Logic TolerANT technology,
see Chapter 1, “General Description.”
Note:

Set this bit if the Enable Ultra SCSI bit in SCSI Control
Three (SCNTL3) is set.

STR

SCSI FIFO Test Read
6
Setting this bit places the SCSI core into a test mode in
which the SCSI FIFO is easily read. Reading the least
significant byte of the SCSI Output Data Latch (SODL)
register causes the FIFO to unload. The functions are
summarized in the table below.
Register
Name

HSC

SCSI Registers

FIFO Bits

FIFO
Function

SODL

Read

[15:0]

Unload

SODL0

Read

[7:0]

Unload

SODL1

Read

[15:8]

None

Halt SCSI Clock
5
Asserting this bit causes the internal divided SCSI clock
to come to a stop in a glitchless manner. This bit is used

4-91

for test purposes or to lower IDD during a power-down
mode.

4-92

DSI

Disable Single Initiator Response
4
If this bit is set, the LSI53C875A ignores all bus-initiated
selection attempts that employ the single initiator option
from SCSI-1. In order to select the LSI53C875A while this
bit is set, the LSI53C875A’s SCSI ID and the initiator’s
SCSI ID must both be asserted. Assert this bit in
SCSI-2 systems so that a single bit error on the SCSI bus
is not interpreted as a single initiator response.

S16

16-Bit System
3
If this bit is set, all devices in the SCSI system
implementation are assumed to be 16-bit. This causes
the LSI53C875A to always check the parity bit for SCSI
IDs [15:8] during bus-initiated selection or reselection,
assuming parity checking has been enabled. If an 8-bit
SCSI device attempts to select the LSI53C875A while
this bit is set, the LSI53C875A will ignore the selection
attempt. This is because the parity bit for IDs [15:8] will
not be driven. See the description of the Enable Parity
Checking bit in the SCSI Control Zero (SCNTL0) register
for more information.

TTM

Timer Test Mode
2
Asserting this bit facilitates testing of the selection
time-out, general purpose, and handshake-to-handshake
timers by greatly reducing all three time-out periods.
Setting this bit starts all three timers and if the respective
bits in the SCSI Interrupt Enable One (SIEN1) register
are asserted, the LSI53C875A generates interrupts at
time-out. This bit is intended for internal manufacturing
diagnosis and should not be used.

CSF

Clear SCSI FIFO
1
Setting this bit causes the “full flags” for the SCSI FIFO
to be cleared. This empties the FIFO. This bit is
self-clearing. In addition to the SCSI FIFO pointers, the
SCSI Input Data Latch (SIDL), SCSI Output Data Latch
(SODL), and (SODR, a hidden buffer register which is not
accessible) full bits in the SCSI Status Zero (SSTAT0)
and SCSI Status Two (SSTAT2) are cleared.

Registers

STW

SCSI FIFO Test Write
0
Setting this bit places the SCSI core into a test mode in
which the FIFO is easily read or written. While this bit is
set, writes to the least significant byte of the SCSI Output
Data Latch (SODL) register cause the entire word
contained in the SODL to be loaded into the FIFO. These
functions are summarized in the table below.
Register
Name

FIFO Bits

FIFO
Function

SODL

Write

[15:0]

Load

SODL0

Write

[7:0]

Load

SODL1

Write

[15:8]

None

Registers: 0x50–0x51
SCSI Input Data Latch (SIDL)
Read Only
15

0
SIDL

SIDL

SCSI Registers

SCSI Input Data Latch
[15:0]
This register is used primarily for diagnostic testing,
programmed I/O operation, or error recovery. Data
received from the SCSI bus can be read from this
register. Data can be written to the SCSI Output Data
Latch (SODL) register and then read back into the
LSI53C875A by reading this register to allow loopback
testing. When receiving SCSI data, the data flows into
this register and out to the host FIFO. This register differs
from the SCSI Bus Data Lines (SBDL) register; SIDL
contains latched data and the SBDL always contains
exactly what is currently on the SCSI data bus. Reading
this register causes the SCSI parity bit to be checked,
and causes a parity error interrupt if the data is not valid.
The power-up values are indeterminate.

4-93

R
x

LOCK
x

Reserved

[7:6]

LOCK

Frequency Lock
5
This bit is used when enabling the SCSI clock quadrupler,
which allows the LSI53C875A to transfer data at Ultra
SCSI rates. Poll this bit for a 1 to determine that the clock
quadrupler has locked. For more information on enabling
the clock quadrupler, refer to the descriptions of SCSI
Test One (STEST1), bits 2 and 3.

Reserved

[4:0]

Registers: 0x54–0x55
SCSI Output Data Latch (SODL)
Read/Write
15

0
SODL

SODL

4-94

Registers

SCSI Output Data Latch
[15:0]
This register is used primarily for diagnostic testing or
programmed I/O operation. Data written to this register is
asserted onto the SCSI data bus by setting the Assert
Data Bus bit in the SCSI Control One (SCNTL1) register.
This register is used to send data using programmed I/O.
Data flows through this register when sending data in any
mode. It is also used to write to the synchronous data
FIFO when testing the chip. The power-up value of this
register is indeterminate.

ENPMJ

PMJCTL

ENNDJ

DISFC

ENPMJ

2
R

DILS

Enable Phase Mismatch Jump
7
Upon setting this bit, any phase mismatches do not
interrupt but force a jump to an alternate location to
handle the phase mismatch. Prior to actually taking the
jump, the appropriate remaining byte counts and
addresses will be calculated such that they can be easily
stored to the appropriate memory location with SCRIPTS
Store instruction.
In the case of a SCSI send, any data in the part will be
automatically cleared after being accounted for. In the
case of a SCSI receive, all data will be flushed out of the
part and accounted for prior to taking the jump. This
feature does not cover, however, the byte that may
appear in SCSI Wide Residue (SWIDE). This byte must
be flushed manually.
This bit also enables the flushing mechanism to flush
data during a Data-In phase mismatch in a more efficient
manner.

PMJCTL

SCSI Registers

Jump Control
6
This bit controls which decision mechanism is used when
jumping on phase mismatch. When this bit is cleared the
LSI53C875A will use Phase Mismatch Jump Address 1
(PMJAD1) when the WSR bit is cleared and
Phase Mismatch Jump Address 2 (PMJAD2) when the
WSR bit is set. When this bit is set the LSI53C875A will
use jump address one (PMJAD1) on data out (data out,
command, message out) transfers and jump address two
(PMJAD2) on data in (data in, status, message in)
transfers. Note that the phase referred to here is the
phase encoded in the block move SCRIPTS instruction,
not the phase on the SCSI bus that caused the phase
mismatch.

4-95

ENNDJ

Enable Jump on Nondata Phase Mismatches
5
This bit controls whether or not a jump is taken during a
nondata phase mismatch (i.e. message in, message out,
status, or command). When this bit is clear, jumps will
only be taken on Data-In or Data-Out phases and a
phase mismatch interrupt will be generated for all other
phases. When this bit is set, jumps will be taken
regardless of the phase in the block move. Note that the
phase referred to here is the phase encoded in the block
move SCRIPTS instruction, not the phase on the SCSI
bus that caused the phase mismatch.

DISFC

Disable Auto FIFO Clear
4
This bit controls whether or not the FIFO is automatically
cleared during a Data-Out phase mismatch. When set,
data in the DMA FIFO as well as data in the SCSI Output
Data Latch (SODL) and SODR, a hidden buffer register
which is not accessible, will not be cleared after
calculations on them are complete. When cleared, the
DMA FIFO and SODL and SODR will automatically be
cleared. This bit also disables the enhanced flushing
mechanism.

Reserved

DILS

Disable Internal Load and Store
This bit controls whether or not Load and Store data
transfers in which the source/destination is located in
SCRIPTS RAM generate external PCI cycles.

[3:2]
1

If cleared, Load and Store data transfers of this type will
NOT generate PCI cycles, but will stay internal to the
chip.
If set, Load and Store data transfers of this type will
generate PCI cycles.
R

4-96

Registers

Reserved

6
R

ZMODE
0

DDAC

64TIMOD

EN64TIBMV

EN64DBMV

ZMODE

High Impedance Mode
7
Setting this bit causes the LSI53C875A to place all output
and bidirectional pins except MAC/_TESTOUT, into a
high impedance state. Also, setting this bit causes all I/O
pins to become inputs, and all pull-ups and pull-downs to
be disabled. When this bit is set, the MAC/_TESTOUT
pin becomes the output pin for the connectivity test of the
LSI53C875A signals in the “AND-tree” test mode. In
order to read data out of the LSI53C875A, this bit must
be cleared. This bit is intended for board-level testing
only. Do not set this bit during normal system operation.

Reserved

DDAC

Disable Dual Address Cycle
3
When this bit is set, all 64-bit addressing as a master will
be disabled. No dual address cycles will be generated by
the LSI53C875A.

[6:4]

When this bit is cleared, the LSI53C875A will generate
dual address cycles based on the master operation being
performed and the value of its associated selector
register.
64TIMOD

64-Bit Table Indirect Indexing Mode
2
When this bit is cleared, bits [24:28] of the first table entry
Dword will select one of 22 possible selectors to be used
in a BMOV operation. When this bit is set, bits [24:31] of
the first table entry Dword will be copied directly into
DNAD64 to provide 40-bit addressing capability. This bit
will only function if the EN64TIBMV bit is set.
Index Mode 0 (64TIMOD clear) table entry format:
[31:29]
Reserved

[28:24]

[23:0]

Sel Index

Byte Count

Source/Destination Address [31:0]

SCSI Registers

4-97

Index Mode 1 (64TIMOD set) table entry format:
[31:24]

[23:0]

Src/Dest Addr [39:32]

Byte Count

Source/Destination Address [31:0]

EN64TIBMV

Enable 64-Bit Table Indirect BMOV
1
Setting this bit enables 64-bit addressing for Table
Indirect BMOVs using the upper byte (bit [24:31]) of the
first Dword of the table entry. When this bit is cleared
table indirect BMOVs will use the Static Block Move
Selector (SBMS) register to obtain the upper 32 bits of
the data address.

EN64DBMV

Enable 64-Bit Direct BMOV
0
Setting this bit enables the 64-bit version of a direct
BMOV. When this bit is cleared direct BMOVs will use the
Static Block Move Selector (SBMS) register to obtain the
upper 32 bits of the data address.

Registers: 0x58–0x59
SCSI Bus Data Lines (SBDL)
Read Only
15

0
SBDL

SBDL

SCSI Bus Data Lines
[15:0]
This register contains the SCSI data bus status. Even
though the SCSI data bus is active low, these bits are
active high. The signal status is not latched and is a true
representation of exactly what is on the data bus at the
time the register is read. This register is used when
receiving data using programmed I/O. This register can
also be used for diagnostic testing or in low level mode.
The power-up value of this register is indeterminate.
If the chip is in the wide mode (SCSI Control Three
(SCNTL3), bit 3 and SCSI Test Two (STEST2), bit 2 are
set) and SBDL is read, both byte lanes are checked for
parity regardless of phase. When in a nondata phase,
this will cause a parity error interrupt to be generated
because the upper byte lane parity is invalid.

4-98

Registers

Registers: 0x5C–0x5F
Scratch Register B (SCRATCHB)
Read/Write
31

0
SCRATCHB

SCRATCHB

Scratch Register B
[31:0]
This is a general purpose user definable scratch pad
register. Apart from CPU access, only register
Read/Write and Memory Moves directed at the
SCRATCH register will alter its contents. The power-up
values are indeterminate. A special mode of this register
can be enabled by setting the PCI Configuration Into
Enable bit in the Chip Test Two (CTEST2) register. If this
bit is set, the SCRATCH B register returns bits [31:12] of
the SCRIPTS RAM PCI Base Address Register Two
(SCRIPTS RAM) in bits [31:12] of the SCRATCH B
register when read. When read, bits [11:0] of SCRATCH
B will always return zeros in this mode. Writes to the
SCRATCH B register are unaffected. Resetting the PCI
Configuration Into Enable bit causes the SCRATCH B
register to return to normal operation.

Registers: 0x60–0x9F
Scratch Registers C–R (SCRATCHC–SCRATCHR)
Read/Write
These are general purpose user definable scratch pad registers. Apart
from CPU access, only register read/write, memory moves and Load and
Stores directed at a SCRATCH register will alter its contents. The
power-up values are indeterminate.

4.3 64-Bit SCRIPTS Selectors
The following registers are used to hold the upper 32-bit addresses for
various SCRIPTS operations. When a particular type of SCRIPTS

64-Bit SCRIPTS Selectors

4-99

operation is performed, one of the six selector registers below will be
used to generate a 64-bit address.
If the selector for a particular device operation is zero, then a standard
32-bit address cycle will be generated. If the selector value is nonzero,
then a DAC will be issued and the 64-bit address will be presented in
two address phases.
All selectors default to 0 (zero) with the exception of the 16 SCRATCH
registers, these power-up in an indeterminate state and should be
initialized before they are used.
All selectors can be read/written using the Load and Store SCRIPTS
instruction, Memory-to-Memory Move, Read/Write SCRIPTS instruction,
or CPU with SCRIPTS not running.
Note:

Crossing of selector boundaries in one memory operation
is not supported.

Registers: 0xA0–0xA3
Memory Move Read Selector (MMRS)
Read/Write
31

0
MMRS

MMRS

Memory Move Read Selector (MMRS)
Supplies the upper Dword of a 64-bit address during data
read operations for Memory-to-Memory Moves and
absolute address LOAD operations.
A special mode of this register can be enabled by setting
the PCI Configuration Enable bit in the Chip Test Two
(CTEST2) register. Because the LSI53C875A supports
only a 32-bit memory mapped PCI base address, the
MMRS register is always read as 0x00000000 when in
the special mode.
Writes to the MMRS register are unaffected. Clearing the
PCI Configuration Into Enable bit causes the MMRS
register to return to normal operation.

4-100

Registers

Registers: 0xA4–0xA7
Memory Move Write Selector (MMWS)
Read/Write
31

0
MMWS

MMWS

Memory Move Write Selector
[31:0]
Supplies the upper Dword of a 64-bit address during data
write operations during Memory-to-Memory Moves and
absolute address STORE operations.
A special mode of this register can be enabled by setting
the PCI Configuration Into Enable bit in the Chip Test Two
(CTEST2) register. Because the LSI53C875A supports
only a 32-bit SCRIPTS RAM PCI base address, the
MMWS register is always read as 0x00000000 when in
the special mode.
Writes to the MMWS register are unaffected. Clearing the
PCI Configuration Enable bit causes the MMWS register
to return to normal operation.

Registers: 0xA8–0xAB
SCRIPTS Fetch Selector (SFS)
Read/Write
31

0
SFS

SFS

SCRIPTS Fetch Selector
[31:0]
Supplies the upper Dword of a 64-bit address during
SCRIPTS fetches and Indirect fetches (excluding Table
Indirect fetches). This register can be loaded
automatically using a 64-bit jump instruction.
A special mode of this register can be enabled by setting
the PCI Configuration Into Enable bit in the Chip Test Two
(CTEST2) register. If this bit is set, bits [23:16] of the SFS
register return the PCI Revision ID (Rev ID) register value
and bits [15:0] return the PCI Device ID register value
when read.

64-Bit SCRIPTS Selectors

4-101

Writes to the SFS register are unaffected. Clearing the
PCI Configuration Into Enable bit causes the SFS register
to return to normal operation.

Registers: 0xAC–0xAF
DSA Relative Selector (DRS)
Read/Write
31

0
DRS

DRS

DSA Relative Selector
[31:0]
Supplies the upper Dword of a 64-bit address during
table indirect fetches and Load and Store Data Structure
Address (DSA) relative operations.

Registers: 0xB0–0xB3
Static Block Move Selector (SBMS)
Read/Write
31

0
SBMS

SBMS

4-102

Registers

Static Block Move Selector
[31:0]
Supplies the upper Dword of a 64-bit address during
block move operations, reads or writes. This register is
static and will not be changed when a 64-bit direct BMOV
is used.

Registers: 0xB4–0xB7
Dynamic Block Move Selector (DBMS)
Read/Write
31

0
DBMS

DBMS

Dynamic Block Move Selector
[31:0]
Supplies the upper Dword of a 64-bit address during
block move operations, reads or writes. This register is
used only during 64-bit direct BMOV instructions and will
be reloaded with the upper 32-bit data address upon
execution of a 64-bit direct BMOVs.

Registers: 0xB8–0xBB
DMA Next Address 64 (DNAD64)
Read/Write
31

0
DNAD64

DNAD64

DMA Next Address 64
[31:0]
This register holds the current selector being used in a
given host transaction. The appropriate selector is copied
to this register prior to beginning a host transaction.

Registers: 0xBC–0xBF
Reserved

4.4 Phase Mismatch Jump Registers
Eight 32-bit registers contain the byte count and addressing information
required to update the direct, indirect, or table indirect BMOV instructions
with new byte counts and addresses. The eight register descriptions
follow.
All registers can be read/written using the Load and Store SCRIPTS
instructions, Memory-to-Memory Moves, read/write SCRIPTS
instructions, or the CPU with SCRIPTS not running.

Phase Mismatch Jump Registers

4-103

Registers: 0xC0–0xC3
Phase Mismatch Jump Address 1 (PMJAD1)
Read/Write
31

0
PMJAD1

PMJAD1

Phase Mismatch Jump Address 1
[31:0]
This register contains the 32-bit address that will be
jumped to upon a phase mismatch. Depending upon the
state of the PMJCTL bit in register Chip Control 0
(CCNTL0) this address will either be used during an
outbound (data out, command, message out) phase
mismatch
(PMJCTL = 0) or when the WSR bit is cleared
(PMJCTL = 1). It should be loaded with an address of a
SCRIPTS routine that will handle the updating of memory
data structures of the BMOV that was executing when the
phase mismatch occurred.

Registers: 0xC4–0xC7
Phase Mismatch Jump Address 2 (PMJAD2)
Read/Write
31

0
PMJAD2

PMJAD2

4-104

Registers

Phase Mismatch Jump Address 2
[31:0]
This register contains the 32-bit address that will be
jumped to upon a phase mismatch. Depending upon the
state of the PMJCTL bit in register Chip Control 0
(CCNTL0) this address will either be used during an
inbound (data in, status, message in) phase mismatch
(PMJCTL = 0) or when the WSR bit is set (PMJCTL = 1).
It should be loaded with an address of a SCRIPTS
routine that will handle the updating of memory data
structures of the BMOV that was executing when the
phase mismatch occurred.

Registers: 0xC8–0xCB
Remaining Byte Count (RBC)
Read/Write
31

0
RBC

RBC

Remaining Byte Count (RBC)
[31:0]
This register contains the byte count that remains for the
BMOV that was executing when the phase mismatch
occurred. In the case of direct or indirect BMOV
instructions, the upper byte of this register will also
contain the opcode of the BMOV that was executing. In
the case of a table indirect BMOV instruction, the upper
byte will contain the upper byte of the table indirect entry
that was fetched.
In the case of a SCSI data receive, this byte count will
reflect all data received from the SCSI bus, including any
byte in SCSI Wide Residue (SWIDE). There will be no
data remaining in the part that must be flushed to
memory with the exception of a possible byte in the
SWIDE register. That byte must be flushed to memory
manually in SCRIPTS.
In the case of a SCSI data send, this byte count will
reflect all data sent out onto the SCSI bus. Any data left
in the part from the phase mismatch will be ignored and
automatically cleared from the FIFOs.

Registers: 0xCC–0xCF
Updated Address (UA)
Read/Write
31

0
UA

Updated Address
[31:0]
This register will contain the updated data address for the
BMOV that was executing when the phase mismatch
occurred.

Phase Mismatch Jump Registers

4-105

In the case of a SCSI data receive, if there is a byte in
the SCSI Wide Residue (SWIDE) register then this
address will point to the location where that byte must be
stored. The SWIDE byte must be manually written to
memory and this address must be incremented prior to
updating any scatter/gather entry.
In the case of a SCSI data receive, if there is not a byte
in the SWIDE register then this address will be the next
location that should be written to when this I/O restarts.
No manual flushing will be necessary.
In the case of a SCSI data send, all data sent to the SCSI
bus will be accounted for and any data left in the part will
be ignored and will be automatically cleared from the
FIFOs.

Registers: 0xD0–0xD3
Entry Storage Address (ESA)
Read/Write
31

0
ESA

This register's value depends on the type of BMOV being executed. The
three types of BMOVs are listed below.
ESA

4-106

Entry Storage Address
[31:0]
This register's value depends on the type of BMOV being
executed. The three types of BMOVs are listed below.

Direct BMOV:

In the case of a direct BMOV, this register will contain
the address the BMOV was fetched from when the
phase mismatch occurred.

Indirect BMOV:

In the case of an indirect BMOV, this register will
contain the address the BMOV was fetched from when
the phase mismatch occurred.

Table Indirect BMOV:

In the case of a table indirect BMOV, this register will
contain the address of the table indirect entry being
used when the phase mismatch occurred.

Registers

Registers: 0xD4–0xD7
Instruction Address (IA)
Read/Write
31

0
IA

Instruction Address
[31:0]
This register always contains the address of the BMOV
instruction that was executing when the phase mismatch
occurred. This value will always match the value in the
Entry Storage Address (ESA) except in the case of a
table indirect BMOV in which case the ESA will have the
address of the table indirect entry and this register will
point to the address of the BMOV instruction.

Registers: 0xD8–0xDA
SCSI Byte Count (SBC)
Read Only
23

0
SBC

SBC

SCSI Byte Count
[23:0]
This register contains the count of the number of bytes
transferred to or from the SCSI bus during any given
BMOV. This value is used in calculating the information
placed into the Remaining Byte Count (RBC) and
Updated Address (UA) register and should not need to be
used in normal operations. There are two conditions in
which this byte count will not match the number of bytes
transferred exactly. If a BMOV is executed to transfer an
odd number of bytes across a wide bus then the byte
count at the end of the BMOV will be greater than the
number of bytes sent by one. This will also happen in an
odd byte count wide receive case. Also, in the case of a
wide send in which there is a chain byte from a previous
transfer, the count will not reflect the chain byte sent
across the bus during that BMOV. The reason for this is
due to the fact that to determine the correct address to
start fetching data from after a phase mismatch this byte

Phase Mismatch Jump Registers

4-107

cannot be counted for this BMOV as it was actually part
of the byte count for the previous BMOV.

Registers: 0xDC–0xDF
Cumulative SCSI Byte Count (CSBC)
Read/Write
31

0
CSBC

CSBC

4-108

Registers

Cumulative SCSI Byte Count
[31:0]
This loadable register contains a cumulative count of the
actual number of bytes that have been transferred across
the SCSI bus during data phases, i.e. it will not count
bytes sent in command, status, message in or message
out phases. It will count bytes as long as the phase
mismatch enable (ENPMJ) bit in the Chip Control 0
(CCNTL0) register is set. Unlike the SCSI Byte Count
(SBC) this count will not be cleared on each BMOV
instruction but will continue to count across multiple
BMOV instructions. This register can be loaded with any
arbitrary start value.

Registers: 0xE0–0xFF
Reserved

Chapter 5
SCSI SCRIPTS
Instruction Set
The LSI53C875A contains a SCSI SCRIPTS processor that permits both
DMA and SCSI commands to be fetched from host memory or internal
SCRIPTS RAM. Algorithms written in SCSI SCRIPTS control the actions
of the SCSI and DMA cores. The SCRIPTS processor executes complex
SCSI bus sequences independently of the host CPU. This chapter
describes the SCSI SCRIPTS Instruction Set used to write these
algorithms. The following sections describe the benefits and use of SCSI
SCRIPTS Instructions.

•

Section 5.1, “Low Level Register Interface Mode”

•

Section 5.2, “High Level SCSI SCRIPTS Mode”

•

Section 5.3, “Block Move Instruction”

•

Section 5.4, “I/O Instruction”

•

Section 5.5, “Read/Write Instructions”

•

Section 5.6, “Transfer Control Instructions”

•

Section 5.7, “Memory Move Instructions”

•

Section 5.8, “Load and Store Instructions”

After power-up and initialization, the LSI53C875A can be operated in the
low level register interface mode or in the high level SCSI SCRIPTS
mode.

5.1 Low Level Register Interface Mode
With the low level register interface mode, the user has access to the
DMA control logic and the SCSI bus control logic. An external processor
has access to the SCSI bus signals and the low level DMA signals, which
allows creation of complicated board level test algorithms. The low level
interface is useful for backward compatibility with SCSI devices that

LSI53C875A PCI to Ultra SCSI Controller

5-1

require certain unique timings or bus sequences to operate properly.
Another feature allowed at the low level is loopback testing. In loopback
mode, the SCSI core can be directed to talk to the DMA core to test
internal data paths all the way out to the chip’s pins.

5.2 High Level SCSI SCRIPTS Mode
To operate in the SCSI SCRIPTS mode, the LSI53C875A requires only
a SCRIPTS start address. The start address must be at a Dword (four
byte) boundary. This aligns subsequent SCRIPTS at a Dword boundary
since all SCRIPTS are 8 or 12 bytes long. Instructions are fetched until
an interrupt instruction is encountered, or until an unexpected event
(such as a hardware error) causes an interrupt to the external processor.
Once an interrupt is generated, the LSI53C875A halts all operations until
the interrupt is serviced. Then, the start address of the next SCRIPTS
instruction may be written to the DMA SCRIPTS Pointer (DSP) register
to restart the automatic fetching and execution of instructions.
The SCSI SCRIPTS mode of execution allows the LSI53C875A to make
decisions based on the status of the SCSI bus, which offloads the
microprocessor from servicing the numerous interrupts inherent in I/O
operations.
Given the rich set of SCSI oriented features included in the instruction
set, and the ability to re-enter the SCSI algorithm at any point, this high
level interface is all that is required for both normal and exception
conditions. Switching to low level mode for error recovery should never
be required.
The following types of SCRIPTS instructions are implemented in the
LSI53C875A, as shown in Table 5.1:

5-2

SCSI SCRIPTS Instruction Set

Table 5.1

SCRIPTS Instructions

Instruction

Description

Block Move

Block Move instruction moves data between the SCSI
bus and memory.

I/O or Read/Write

I/O or Read/Write instructions cause the LSI53C875A to
trigger common SCSI hardware sequences, or to move
registers.

Transfer Control

Transfer Control instruction allows SCRIPTS instructions
to make decisions based on real time SCSI bus
conditions.

Memory Move

Memory Move instruction causes the LSI53C875A to
execute block moves between different parts of main
memory.

Load and Store

Load and Store instructions provide a more efficient way
to move data to/from memory from/to an internal register
in the chip without using the Memory Move instruction.

Each instruction consists of two or three 32-bit words. The first 32-bit
word is always loaded into the DMA Command (DCMD) and DMA Byte
Counter (DBC) registers, the second into the DMA SCRIPTS Pointer
Save (DSPS) register. The third word, used only by Memory Move
instructions, is loaded into the Temporary (TEMP) shadow register. In an
indirect I/O or Move instruction, the first two 32-bit opcode fetches is
followed by one or two more 32-bit fetch cycles.

5.2.1 Sample Operation
This sample operation describes execution of a SCRIPTS instruction for
a Block Move instruction.

•

The host CPU, through programmed I/O, gives the DMA SCRIPTS
Pointer (DSP) register (in the Operating register file) the starting
address in main memory that points to a SCSI SCRIPTS program
for execution.

•

Loading the DMA SCRIPTS Pointer (DSP) register causes the
LSI53C875A to fetch its first instruction at the address just loaded.
This is from main memory or the internal RAM, depending on the
address.

High Level SCSI SCRIPTS Mode

5-3

•

The LSI53C875A typically fetches two Dwords (64 bits) and decodes
the high order byte of the first longword as a SCRIPTS instruction. If
the instruction is a Block Move, the lower three bytes of the first
longword are stored and interpreted as the number of bytes to be
moved. The second longword is stored and interpreted as the 32-bit
beginning address in main memory to which the move is directed.

•

For a SCSI send operation, the LSI53C875A waits until there is
enough space in the DMA FIFO to transfer a programmable size
block of data. For a SCSI receive operation, it waits until enough data
is collected in the DMA FIFO for transfer to memory. At this point,
the LSI53C875A requests use of the PCI bus again to transfer the
data.

•

When the LSI53C875A is granted the PCI bus, it executes (as a bus
master) a burst transfer (programmable size) of data, decrement the
internally stored remaining byte count, increment the address
pointer, and then release the PCI bus. The LSI53C875A stays off the
PCI bus until the FIFO can again hold (for a write) or has collected
(for a read) enough data to repeat the process.

The process repeats until the internally stored byte count has reached
zero. The LSI53C875A releases the PCI bus and then performs another
SCRIPTS instruction fetch cycle, using the incremented stored address
maintained in the DMA SCRIPTS Pointer (DSP) register. Execution of
SCRIPTS instructions continues until an error condition occurs or an
interrupt SCRIPTS instruction is received. At this point, the LSI53C875A
interrupts the host CPU and waits for further servicing by the host
system. It can execute independent Block Move instructions specifying
new byte counts and starting locations in main memory. In this manner,
the LSI53C875A performs scatter/gather operations on data without
requiring help from the host program, generating a host interrupt, or
requiring an external DMA controller to be programmed. An overview of
this process is presented in Figure 5.1.

5-4

SCSI SCRIPTS Instruction Set

Figure 5.1

SCRIPTS Overview

System Processor
Write DSA

System Memory
SCSI Initiator Write Example

× Select ATN 0, alt_addr
× Move from identify_msg_buf,
when MSG_OUT
× Move from data_buf when DATA_OUT
× Move from stat_in_buf, when STATUS
× Move SCNTL2 & 7F to SCNTL2
× Clear ACK
× Wail disconnect alt2
× Int 10

Table
byte count
address

S
Y
S
T
E
M

Write
DSP

Fetch

C SCRIPTS
I

LSI53C875A

SCSI Bus

For details,
see block
diagram in
Chapter 2

B
U
S

byte count
address
byte count
address

Data

byte count
address
Data Structure
Message Buffer
Command Buffer
Data Buffer
Status Buffer

High Level SCSI SCRIPTS Mode

5-5

5.3 Block Move Instruction
Performing a Block Move instruction, bit 5, Source I/O - Memory Enable
(SIOM) and bit 4, Destination I/O - Memory Enable (DIOM) in the DMA
Mode (DMODE) register determines whether the source/destination
address resides in memory or I/O space. When data is being moved onto
the SCSI bus, SIOM controls whether that data comes from I/O or
memory space. When data is being moved off of the SCSI bus, DIOM
controls whether that data goes to I/O or memory space.

5.3.1 First Dword
31 30 29 28

24 23

DMA Command (DCMD) Register

DMA Byte Counter (DBC) Register

IT[1:0] IA TIA OPC SCSIP[2:0]

Transfer Counter [23:0]

IT[1:0]

Instruction Type - Block Move
[31:30]
The IT bit configuration (00) defines a Block Move
Instruction Type.

Indirect Addressing
29
This bit determines if addressing is direct or indirect.
If IA bit is (0), use destination field as an address (direct
addressing). If IA bit is (1), use destination field as a
pointer to an address (indirect addressing).
When this bit is zero, user data is moved to or from the
32-bit data start address for the Block Move instruction.
The value is loaded into the chip’s address register and
incremented as data is transferred. The address of the
data to move is in the second Dword of this instruction.
When this bit is one, the 32-bit user data start address
for the Block Move is the address of a pointer to the
actual data buffer address. The value at the 32-bit start
address is loaded into the chip’s DMA Next Address
(DNAD) register using a third longword fetch (4-byte
transfer across the host computer bus).

5-6

SCSI SCRIPTS Instruction Set

Direct Addressing
The byte count and absolute address are:
Command

Byte Count
Address of Data

Indirect Addressing
Use the fetched byte count, but fetch the data address
from the address in the instruction.
Command

Byte Count
Address of Pointer to Data

Once the data pointer address is loaded, it is executed
as when the chip operates in the direct mode. This
indirect feature allows a table of data buffer addresses to
be specified. Using the SCSI SCRIPTS assembler, the
table offset is placed in the script at compile time. Then
at the actual data transfer time, the offsets are added to
the base address of the data address table by the
external processor. The logical I/O driver builds a
structure of addresses for an I/O rather than treating each
address individually. This feature makes it possible to
locate SCSI SCRIPTS in a PROM.
Note:

TIA

Do not use indirect and table indirect addressing
simultaneously; use only one addressing method at a time.
Table Indirect
32-Bit Addressing

When this bit is set, the 24-bit signed value in the start
address of the move is treated as a relative displacement
from the value in the Data Structure Address (DSA)
register. Both the transfer count and the source/
destination address are fetched from this location.
Use the signed integer offset in bits [23:0] of the second
four bytes of the instruction, added to the value in the
Data Structure Address (DSA) register, to fetch first the
byte count and then the data address. The signed value
is combined with the data structure base address to
generate the physical address used to fetch values from

Block Move Instruction

5-7

the data structure. Sign extended values of all ones for
negative values are allowed, but bits [31:24] are ignored.

Note:

Command

Not Used

Don’t Care

Table Offset

Do not use indirect and table indirect addressing
simultaneously; use only one addressing method at a time.
Prior to the start of an I/O, the Data Structure Address
(DSA) register should be loaded with the base address of
the I/O data structure. The address may be any address
on a longword boundary.
After a Table Indirect opcode is fetched, the DSA is
added to the 24-bit signed offset value from the opcode
to generate the address of the required data; both
positive and negative offsets are allowed. A subsequent
fetch from that address brings the data values into the
chip.
For a MOVE instruction, the 24-bit byte count is fetched
from system memory. Then the 32-bit physical address is
brought into the LSI53C875A. Execution of the move
begins at this point.
SCRIPTS can directly execute operating system I/O data
structures, saving time at the beginning of an I/O
operation. The I/O data structure can begin on any
longword boundary and may cross system segment
boundaries.
There are two restrictions on the placement of pointer
data in system memory:

• The eight bytes of data in the MOVE instruction must
be contiguous, as shown below, and

• Indirect data fetches are not available during
execution of a Memory-to-Memory DMA operation.
00

Byte Count
Physical Data Address

5-8

SCSI SCRIPTS Instruction Set

OPC

OpCode
27
This 1-bit OpCode field defines the type of Block Move
(MOVE) Instruction to be preformed in Target and Initiator
mode.
Target Mode
In Target mode, the OpCode bit defines the following
operations:
OPC

Instruction Defined

MOVE/MOVE64

CHMOV/CHMOV64

These instructions perform the following steps:
1. The LSI53C875A verifies that it is connected to the SCSI
bus as a Target before executing this instruction.
2. The LSI53C875A asserts the SCSI phase signals (SMSG/,
SC_D/, and SI_O/) as defined by the Phase Field bits in the
instruction.
3. If the instruction is for the command phase, the
LSI53C875A receives the first command byte and decodes
its SCSI Group Code.
–

If the SCSI Group Code is either Group 0, Group 1,
Group 2, or Group 5, and if the Vendor Unique
Enhancement 1 (VUE1) bit (SCNTL2 bit 1) is clear, then
the LSI53C875A overwrites the DMA Byte Counter
(DBC) register with the length of the Command
Descriptor Block: 6, 10, or 12 bytes.

–

If the Vendor Unique Enhancement 1 (VUE1) bit
(SCNTL2 bit 1) is set, the LSI53C875A receives the
number of bytes in the byte count regardless of the
group code.

–

If the Vendor Unique Enhancement 1 bit is clear and
group code is vendor unique, the LSI53C875A receives
the number of bytes in the count.

–

If any other Group Code is received, the DMA Byte
Counter (DBC) register is not modified and the
LSI53C875A requests the number of bytes specified in
the DMA Byte Counter (DBC) register. If the DBC

Block Move Instruction

5-9

register contains 0x000000, an illegal instruction
interrupt is generated.
4. The LSI53C875A transfers the number of bytes specified in
the DBC register starting at the address specified in the
DMA Next Address (DNAD) register. If the OpCode bit is
set and a data transfer ends on an odd byte boundary, the
LSI53C875A stores the last byte in the SCSI Wide Residue
(SWIDE) register during a receive operation. This byte is
combined with the first byte from the subsequent transfer
so that a wide transfer can be completed.
5. If the SATN/ signal is asserted by the Initiator or a parity
error occurred during the transfer, the transfer can
optionally be halted and an interrupt generated. The
Disable Halt on Parity Error or ATN bit in the SCSI Control
One (SCNTL1) register controls whether the LSI53C875A
halts on these conditions immediately, or waits until
completion of the current Move.
Initiator Mode
In Target mode, the OpCode bit defines the following
operations:
OPC

Instruction Defined

CHMOV

MOVE

These instructions perform the following steps:
1. The LSI53C875A verifies that it is connected to the SCSI
bus as an Initiator before executing this instruction.
2. The LSI53C875A waits for an unserviced phase to occur.
An unserviced phase is any phase (with SREQ/ asserted)
for which the LSI53C875A has not yet transferred data by
responding with a SACK/.
3. The LSI53C875A compares the SCSI phase bits in the
DMA Command (DCMD) register with the latched SCSI
phase lines stored in the SCSI Status One (SSTAT1)

5-10

SCSI SCRIPTS Instruction Set

register. These phase lines are latched when SREQ/ is
asserted.
4. If the SCSI phase bits match the value stored in the SCSI
SCSI Status One (SSTAT1) register, the LSI53C875A
transfers the number of bytes specified in the DMA Byte
Counter (DBC) register starting at the address pointed to
by the DMA Next Address (DNAD) register. If the OpCode
bit is cleared and a data transfer ends on an odd byte
boundary, the LSI53C875A stores the last byte in the SCSI
Wide Residue (SWIDE) register during a receive operation,
or in the SCSI Output Data Latch (SODL) register during a
send operation. This byte is combined with the first byte
from the subsequent transfer so that a wide transfer can
complete.
5. If the SCSI phase bits do not match the value stored in the
SCSI Status One (SSTAT1) register, the LSI53C875A
generates a phase mismatch interrupt and the instruction is
not executed.
6. During a Message-Out phase, after the LSI53C875A has
performed a select with Attention (or SATN/ is manually
asserted with a Set ATN instruction), the LSI53C875A
deasserts SATN/ during the final SREQ/SACK/ handshake.
7. When the LSI53C875A is performing a block move for
Message-In phase, it does not deassert the SACK/ signal
for the last SREQ/SACK/ handshake. Clear the SACK/
signal using the Clear SACK I/O instruction.
SCSIP[2:0]

SCSI Phase
[26:24]
This 3-bit field defines the SCSI information transfer
phase. When the LSI53C875A operates in Initiator mode,
these bits are compared with the latched SCSI phase bits
in the SCSI Status One (SSTAT1) register. When the
LSI53C875A operates in Target mode, it asserts the
phase defined in this field. Table 5.2 describes the
possible combinations and the corresponding SCSI
phase.

Block Move Instruction

5-11

TC[23:0]

Table 5.2

SCSI Information Transfer Phase

MSG C_D

I_O

SCSI Phase

Data-Out

Data-In

Command

Status

Reserved

Message-Out

Message-In

Transfer Counter
[23:0]
This 24-bit field specifies the number of data bytes to be
moved between the LSI53C875A and system memory.
The field is stored in the DMA Byte Counter (DBC)
register. When the LSI53C875A transfers data to/from
memory, the DBC register is decremented by the number
of bytes transferred. In addition, the DMA Next Address
(DNAD) register is incremented by the number of bytes
transferred. This process is repeated until the DBC
register is decremented to zero. At this time, the
LSI53C875A fetches the next instruction.
If bit 28 is set, indicating table indirect addressing, this
field is not used. The byte count is instead fetched from
a table pointed to by the Data Structure Address (DSA)
register.

5-12

SCSI SCRIPTS Instruction Set

5.3.2 Second Dword
31

0
DMA SCRIPTS Pointer Save (DSPS) Register

Start Address
[31:0]
This 32-bit field specifies the starting address of the data
to move to/from memory. This field is copied to the DMA
Next Address (DNAD) register. When the LSI53C875A
transfers data to or from memory, the DNAD register is
incremented by the number of bytes transferred.
When bit 29 is set, indicating indirect addressing, this
address is a pointer to an address in memory that points
to the data location. When bit 28 is set, indicating table
indirect addressing, the value in this field is an offset into
a table pointed to by the Data Structure Address (DSA).
The table entry contains byte count and address
information.

5.4 I/O Instruction
I/O Instructions perform the following SCSI operations in Target and
Initiator mode. These I/O operations are chosen with the opcode bits in
the DMA Command (DCMD) register.
OPC2

OPC1

OPC0

Target Mode

Initiator Mode

Reselect

Select

Disconnect

Wait Disconnect

Wait Select

Wait Reselect

Set

Clear

This section describes these I/O operations.

I/O Instruction

5-13

5.4.1 First Dword
31 30 29

27 26 25 24 23

20 19

16 15

DMA Command (DCMD)
Register

8 7

5 4

ACK

ATN

0 0

DMA Byte Counter (DBC) Register

IT[1:0] OPC[2:0] RA TI Sel
0

11 10 9

R
0

ENDID[3:0]
0

CC TM

0 0 0 0 0

R
0

IT[1:0]

Instruction Type - I/O Instruction
[31:30]
The IT bit configuration (01) defines an I/O Instruction
Type.

OPC[2:0]

OpCode
[29:27]
The OpCode bit configurations define the I/O operation
performed but the OpCode bit meanings change in Target
mode compared to Initiator mode. OpCode bit
configurations (101, 110, and 111) are considered
Read/Write instructions, and are described in Section
5.5, “Read/Write Instructions.” This section describes
Target mode operations.
Target Mode
OPC2 OPC1 OPC0

Instruction Defined

Reselect

Disconnect

Wait Select

Set

Clear

Reselect Instruction
The LSI53C875A arbitrates for the SCSI bus by asserting
the SCSI ID stored in the SCSI Chip ID (SCID) register.
If it loses arbitration, it tries again during the next
available arbitration cycle without reporting any lost
arbitration status.
If the LSI53C875A wins arbitration, it attempts to reselect
the SCSI device whose ID is defined in the destination ID
field of the instruction. Once the LSI53C875A wins
arbitration, it fetches the next instruction from the address
pointed to by the DMA SCRIPTS Pointer (DSP) register.

5-14

SCSI SCRIPTS Instruction Set

This way the SCRIPTS can move on to the next
instruction before the reselection completes. It continues
executing SCRIPTS until a SCRIPT that requires a
response from the Initiator is encountered.
If the LSI53C875A is selected or reselected before
winning arbitration, it fetches the next instruction from the
address pointed to by the 32-bit jump address field stored
in the DMA Next Address (DNAD) register. Manually set
the LSI53C875A to Initiator mode if it is reselected, or to
Target mode if it is selected.
Disconnect Instruction
The LSI53C875A disconnects from the SCSI bus by
deasserting all SCSI signal outputs.
Wait Select Instruction
If the LSI53C875A is selected, it fetches the next
instruction from the address pointed to by the DMA
SCRIPTS Pointer (DSP) register.
If reselected, the LSI53C875A fetches the next instruction
from the address pointed to by the 32-bit jump address
field stored in the DMA Next Address (DNAD) register.
Manually set the LSI53C875A to Initiator mode when it is
reselected.
If the CPU sets the SIGP bit in the Interrupt Status Zero
(ISTAT0) register, the LSI53C875A aborts the Wait Select
instruction and fetches the next instruction from the
address pointed to by the 32-bit jump address field stored
in the DMA Next Address (DNAD) register.
Set Instruction
When the SACK/ or SATN/ bits are set, the
corresponding bits in the SCSI Output Control Latch
(SOCL) register are set. Do not set SACK/ or SATN/
except for testing purposes. When the target bit is set,
the corresponding bit in the SCSI Control Zero (SCNTL0)
register is also set. When the carry bit is set, the
corresponding bit in the Arithmetic Logic Unit (ALU) is
set.
Note:

None of the signals are set on the SCSI bus in Target
mode.
Clear Instruction

I/O Instruction

5-15

When the SACK/ or SATN/ bits are cleared, the
corresponding bits are cleared in the
SCSI Output Control Latch (SOCL) register. Do not set
SACK/ or SATN/ except for testing purposes. When the
target bit is cleared, the corresponding bit in the SCSI
Control Zero (SCNTL0) register is cleared. When the
carry bit is cleared, the corresponding bit in the ALU is
cleared.
Note:

None of the signals are cleared on the SCSI bus in the
Target mode.
Initiator Mode
OPC2

OPC1

OPC0 Instruction Defined

Select

Wait Disconnect

Wait Reselect

Set

Clear

Select Instruction
The LSI53C875A arbitrates for the SCSI bus by asserting
the SCSI ID stored in the SCSI Chip ID (SCID) register.
If it loses arbitration, it tries again during the next
available arbitration cycle without reporting any lost
arbitration status.
If the LSI53C875A wins arbitration, it attempts to select
the SCSI device whose ID is defined in the destination ID
field of the instruction. Once the LSI53C875A wins
arbitration, it fetches the next instruction from the address
pointed to by the DMA SCRIPTS Pointer (DSP) register.
This way the SCRIPTS can move to the next instruction
before the selection completes. It continues executing
SCRIPTS until a SCRIPT that requires a response from
the Target is encountered.
If the LSI53C875A is selected or reselected before
winning arbitration, it fetches the next instruction from the
address pointed to by the 32-bit jump address field stored
in the DMA Next Address (DNAD) register. Manually set

5-16

SCSI SCRIPTS Instruction Set

the LSI53C875A to Initiator mode if it is reselected, or to
Target mode if it is selected.
If the Select with SATN/ field is set, the SATN/ signal is
asserted during the selection phase.
Wait Disconnect Instruction
The LSI53C875A waits for the Target to perform a “legal”
disconnect from the SCSI bus. A “legal” disconnect
occurs when SBSY/ and SSEL/ are inactive for a
minimum of one Bus Free delay (400 ns), after the
LSI53C875A receives a Disconnect Message or a
Command Complete Message.
Wait Reselect Instruction
If the LSI53C875A is selected before being reselected, it
fetches the next instruction from the address pointed to
by the 32-bit jump address field stored in the DMA Next
Address (DNAD) register. Manually set the LSI53C875A
to Target mode when it is selected.
If the LSI53C875A is reselected, it fetches the next
instruction from the address pointed to by the DMA
SCRIPTS Pointer (DSP) register.
If the CPU sets the SIGP bit in the Interrupt Status Zero
(ISTAT0) register, the LSI53C875A aborts the Wait
Reselect instruction and fetches the next instruction from
the address pointed to by the 32-bit jump address field
stored in the DMA Next Address (DNAD) register.
Set Instruction
When the SACK/ or SATN/ bits are set, the
corresponding bits in the SCSI Output Control Latch
(SOCL) register are set. When the target bit is set, the
corresponding bit in the SCSI Control Zero (SCNTL0)
register is also set. When the carry bit is set, the
corresponding bit in the ALU is set.
Clear Instruction
When the SACK/ or SATN/ bits are cleared, the
corresponding bits are cleared in the SCSI Output Control Latch (SOCL) register. When the target bit is cleared,
the corresponding bit in the SCSI Control Zero (SCNTL0)
register is cleared. When the carry bit is cleared, the
corresponding bit in the ALU is cleared.

I/O Instruction

5-17

Relative Addressing Mode
26
When this bit is set, the 24-bit signed value in the DMA
Next Address (DNAD) register is used as a relative
displacement from the current DMA SCRIPTS Pointer
(DSP) address. Use this bit only in conjunction with the
Select, Reselect, Wait Select, and Wait Reselect
instructions. The Select and Reselect instructions can
contain an absolute alternate jump address or a relative
transfer address.

Table Indirect Mode
25
When this bit is set, the 24-bit signed value in the DMA
Byte Counter (DBC) register is added to the value in the
Data Structure Address (DSA) register, and used as an
offset relative to the value in the Data Structure Address
(DSA) register. The SCSI Control Three (SCNTL3) value,
SCSI ID, synchronous offset and synchronous period are
loaded from this address. Prior to the start of an I/O, load
the Data Structure Address (DSA) with the base address
of the I/O data structure. Any address on a Dword
boundary is allowed. After a Table Indirect opcode is
fetched, the Data Structure Address (DSA) is added to
the 24-bit signed offset value from the opcode to
generate the address of the required data. Both positive
and negative offsets are allowed. A subsequent fetch
from that address brings the data values into the chip.
SCRIPTS can directly execute operating system I/O data
structures, saving time at the beginning of an I/O
operation. The I/O data structure can begin on any Dword
boundary and may cross system segment boundaries.
There are two restrictions on the placement of data in
system memory:

• The I/O data structure must lie within the 8 Mbytes
above or below the base address.

• An I/O command structure must have all four bytes
contiguous in system memory, as shown below. The
offset/period bits are ordered as in the SCSI Transfer
(SXFER) register. The configuration bits are ordered
as in the SCSI Control Three (SCNTL3) register.
Config

5-18

SCSI SCRIPTS Instruction Set

Offset/period

Use this bit only in conjunction with the Select, Reselect,
Wait Select, and Wait Reselect instructions. Use bits 25
and 26 individually or in= combination to produce the
following conditions:
Bit 25

Bit 26

Direct

Table Indirect

Relative

Table Relative

Direct
Uses the device ID and physical address in the
instruction.
Command

Not Used

Absolute Alternate Address

Table Indirect
Uses the physical jump address, but fetches data using
the table indirect method.
Command

Table Offset
Absolute Alternate Address

Relative
Uses the device ID in the instruction, but treats the
alternate address as a relative jump.
Command

Not Used

Absolute Jump Offset

I/O Instruction

5-19

Table Relative
Treats the alternate jump address as a relative jump and
fetches the device ID, synchronous offset, and
synchronous period indirectly. The value in bits [23:0] of
the first four bytes of the SCRIPTS instruction is added
to the data structure base address to form the fetch
address.
Command

Table Offset
Absolute Jump Offset

5-20

Sel

Select with ATN/
24
This bit specifies whether SATN/ is asserted during the
selection phase when the LSI53C875A is executing a
Select instruction. When operating in Initiator mode, set
this bit for the Select instruction. If this bit is set on any
other I/O instruction, an illegal instruction interrupt is
generated.

Reserved

ENDID[3:0]

Encoded SCSI Destination ID
[19:16]
This 4-bit field specifies the destination SCSI ID for an I/O
instruction.

Reserved

Set/Clear Carry
10
This bit is used in conjunction with a Set or Clear
instruction to set or clear the Carry bit. Setting this bit
with a Set instruction asserts the Carry bit in the ALU.
Clearing this bit with a Clear instruction deasserts the
Carry bit in the ALU.

Set/Clear Target Mode
9
This bit is used in conjunction with a Set or Clear
instruction to set or clear Target mode. Setting this bit
with a Set instruction configures the LSI53C875A as a
Target device (this sets bit 0 of the SCSI Control Zero
(SCNTL0) register). Clearing this bit with a Clear
instruction configures the LSI53C875A as an Initiator
device (this clears bit 0 of the SCNTL0 register).

SCSI SCRIPTS Instruction Set

[23:20]

[15:11]

Reserved

[8:7]

ACK

Set/Clear SACK/

Reserved

ATN

Set/Clear SATN/
3
These two bits are used in conjunction with a Set or Clear
instruction to assert or deassert the corresponding SCSI
control signal. Bit 6 controls the SCSI SACK/ signal. Bit 3
controls the SCSI SATN/ signal.

6
[5:4]

The Set instruction is used to assert SACK/ and/or SATN/
on the SCSI bus. The Clear instruction is used to
deassert SACK/ and/or SATN/ on the SCSI bus. The
corresponding bit in the SCSI Output Control Latch
(SOCL) register is set or cleared depending on the
instruction used.
Since SACK/ and SATN/ are Initiator signals, they are not
asserted on the SCSI bus unless the LSI53C875A is
operating as an Initiator or the SCSI Loopback Enable bit
is set in the SCSI Test Two (STEST2) register.
The Set/Clear SCSI ACK/, ATN/ instruction is used after
message phase Block Move operations to give the
Initiator the opportunity to assert attention before
acknowledging the last message byte. For example, if the
Initiator wishes to reject a message, it issues an Assert
SCSI ATN instruction before a Clear SCSI ACK
instruction.
R

Reserved

[2:0]

5.4.2 Second Dword
31

0
DMA SCRIPTS Pointer Save (DSPS) Register

I/O Instruction

Start Address
[31:0]
This 32-bit field contains the memory address to fetch the
next instruction if the selection or reselection fails.

5-21

If relative or table relative addressing is used, this value
is a 24-bit signed offset relative to the current DMA
SCRIPTS Pointer (DSP) register value.

5.5 Read/Write Instructions
The Read/Write instruction supports addition, subtraction, and
comparison of two separate values within the chip. It performs the
desired operation on the specified register and the SCSI First Byte
Received (SFBR) register, then stores the result back to the specified
register or the SFBR. If the COM bit DMA Control (DCNTL bit 0) is
cleared, Read/Write instructions cannot be used.

5.5.1 First Dword
31 30 29

27 26

24 23 22

16 15

DMA Command (DCMD)
Register
IT[1:0] OPC[2:0]
0

5-22

O[2:0]
x

DMA Byte Counter (DBC) Register
D8

A[6:0]
x

ImmD
x

A7 Reserved - Must be 0
x

IT[1:0]

Instruction Type - Read/Write Instruction
[31:30]
The configuration of the IT bits, the OpCode bits and the
Operator bits define the Read/Write Instruction Type. The
configuration of all these bits determine which instruction
is currently selected.

OPC[2:0]

OpCode
[29:27]
The combinations of these bits determine if the
instruction is a Read/Write or an I/O instruction. OpCodes
0b000 through 0b100 are considered I/O instructions.

O[2:0]

Operator
[26:24]
These bits are used in conjunction with the opcode bits
to determine which instruction is currently selected. Refer
to Table 5.1 for field definitions.

Use data8/SFBR
23
When this bit is set, SFBR is used instead of the data8
value during a Read-Modify-Write instruction (see
Table 5.1). This allows the user to add two register
values.

SCSI SCRIPTS Instruction Set

A[6:0]

Register Address - A[6:0]
[22:16]
It is possible to change register values from SCRIPTS in
read-modify-write cycles or move to/from SFBR cycles.
A[6:0] selects an 8-bit source/destination register within
the LSI53C875A.

ImmD

Immediate Data
[15:8]
This 8-bit value is used as a second operand in logical
and arithmetic functions.

Upper Register Address Line [A7]
This bit is used to access registers 0x80–0xFF.

Reserved

7
[6:0]

5.5.2 Second Dword
31

0
DMA SCRIPTS Pointer Save (DSPS) Register

Destination Address
[31:0]
This field contains the 32-bit destination address where
the data is to move.

5.5.3 Read-Modify-Write Cycles
During these cycles the register is read, the selected operation is
performed, and the result is written back to the source register.
The Add operation is used to increment or decrement register values (or
memory values if used in conjunction with a Memory-to-Register Move
operation) for use as loop counters.
Subtraction is not available when SFBR is used instead of data8 in the
instruction syntax. To subtract one value from another when using SFBR,
first XOR the value to subtract (subtrahend) with 0xFF, and add 1 to the
resulting value. This creates the 2’s complement of the subtrahend. The
two values are then added to obtain the difference.

Read/Write Instructions

5-23

5.5.4 Move To/From SFBR Cycles
All operations are read-modify-writes. However, two registers are
involved, one of which is always the SFBR. Table 5.3 shows the possible
read-modify-write operations. The possible functions of this instruction
are:

Table 5.3

•

Write one byte (value contained within the SCRIPTS instruction) into
any chip register.

•

Move to/from the SFBR from/to any other register.

•

Alter the value of a register with AND, OR, ADD, XOR, SHIFT LEFT,
or SHIFT RIGHT operators.

•

After moving values to the SFBR, the compare and jump, call, or
similar instructions are used to check the value.

•

A Move-to-SFBR followed by a Move-from-SFBR is used to perform
a register-to-register move.

Read/Write Instructions
OpCode 111
Read-Modify-Write

OpCode 110
Move to SFBR

OpCode 101
Move from SFBR

000

Move data into register.
Syntax: “Move data8 to
RegA”

Move data into SCSI First
Byte Received (SFBR)
register. Syntax: “Move
data8 to SFBR”

Move data into register.
Syntax: “Move data8 to
RegA”

0011

Shift register one bit to the
left and place the result in
the same register. Syntax:
“Move RegA SHL RegA”

Shift register one bit to the
left and place the result in
the SCSI First Byte
Received (SFBR) register.
Syntax: “Move RegA SHL
SFBR”

Shift the SFBR register one
bit to the left and place the
result in the register. Syntax:
“Move SFBR SHL RegA”

010

OR data with register and
place the result in the same
register. Syntax: “Move
RegA | data8 to RegA”

OR data with register and
place the result in the SCSI
First Byte Received (SFBR)
register. Syntax: “Move
RegA | data8 to SFBR”

OR data with SFBR and
place the result in the
register. Syntax: “Move
SFBR | data8 to RegA”

011

XOR data with register and
place the result in the same
register. Syntax: “Move
RegA XOR data8 to RegA”

XOR data with register and
place the result in the SCSI
First Byte Received (SFBR)
register. Syntax: “Move
RegA XOR data8 to SFBR”

XOR data with SFBR and
place the result in the
register. Syntax: “Move
SFBR XOR data8 to RegA”

Operator

5-24

SCSI SCRIPTS Instruction Set

Table 5.3

Read/Write Instructions (Cont.)
OpCode 111
Read-Modify-Write

OpCode 110
Move to SFBR

OpCode 101
Move from SFBR

100

AND data with register and
place the result in the same
register. Syntax: “Move
RegA & data8 to RegA”

AND data with register and
place the result in the SCSI
First Byte Received (SFBR)
register. Syntax: “Move
RegA & data8 to SFBR”

AND data with SFBR and
place the result in the
register. Syntax: “Move
SFBR & data8 to RegA”

1011

Shift register one bit to the
right and place the result in
the same register. Syntax:
“Move RegA SHR RegA”

Shift register one bit to the
right and place the result in
the SCSI First Byte
Received (SFBR) register.
Syntax: “Move RegA SHR
SFBR”

Shift the SFBR register one
bit to the right and place the
result in the register. Syntax:
“Move SFBR SHR RegA”

110

Add data to register without
carry and place the result
in the same register.
Syntax: “Move RegA +
data8 to RegA”

Add data to register without
carry and place the result in
the SCSI First Byte
Received (SFBR) register.
Syntax: “Move RegA + data8
to SFBR”

Add data to SFBR without
carry and place the result in
the register. Syntax: “Move
SFBR + data8 to RegA”

111

Add data to register with
carry and place the result
in the same register.
Syntax: “Move RegA +
data8 to RegA with carry”

Add data to register with
carry and place the result in
the SCSI First Byte
Received (SFBR) register.
Syntax: “Move RegA + data8
to SFBR with carry”

Add data to SFBR with carry
and place the result in the
register. Syntax: “Move
SFBR + data8 to RegA with
carry”

Operator

1. Data is shifted through the Carry bit and the Carry bit is shifted into the data byte.
Miscellaneous Notes:
• Substitute the desired register name or address for “RegA” in the syntax examples.
• data8 indicates eight bits of data.
• Use SFBR instead of data8 to add two register values.

5.6 Transfer Control Instructions
This section describes the Transfer Control Instructions. The
configuration of the OpCode bits define which Transfer Control Instruction
to perform.

Transfer Control Instructions

5-25

5.6.1 First Dword
31 30 29

27 26

24 23 22 21 20 19

18 17

DMA Command (DCMD)
Register

16 15

DMA Byte Counter (DBC) Register
DCM-Data Compare
Mask

IT[1:0] OPC[2:0] SCSIP[2:0] RA R CT IF JMP CD CP WVP
1

8 7

x x x x x x x

DCV-Data Compare
Value
x

x x x x x x x

IT[1:0]

Instruction Type - Transfer Control
Instruction
[31:30]
The IT bit configuration (10) defines the Transfer Control
Instruction Type.

OPC[2:0]

OpCode
[29:27]
This 3-bit field specifies the type of Transfer Control
Instruction to execute. All Transfer Control Instructions
can be conditional. They can be dependent on a
true/false comparison of the ALU Carry bit or a
comparison of the SCSI information transfer phase with
the Phase field, and/or a comparison of the First Byte
Received with the Data Compare field. Each instruction
can operate in Initiator or Target mode. Transfer Control
Instructions are shown in Table 5.4.
Table 5.4

Transfer Control Instructions

OPC2

OPC1

OPC0

Instruction Defined

Jump

Call

Return

Interrupt

Reserved

Jump Instruction
The LSI53C875A can do a true/false comparison of the
ALU carry bit, or compare the phase and/or data as
defined by the Phase Compare, Data Compare and
True/False bit fields.
If the comparisons are true, then it loads the DMA
SCRIPTS Pointer (DSP) register with the contents of the

5-26

SCSI SCRIPTS Instruction Set

DMA SCRIPTS Pointer Save (DSPS) register. The DSP
register now contains the address of the next instruction.
If the comparisons are false, the LSI53C875A fetches the
next instruction from the address pointed to by the DMA
SCRIPTS Pointer (DSP) register, leaving the instruction
pointer unchanged.
Call Instruction
The LSI53C875A can do a true/false comparison of the
ALU carry bit, or compare the phase and/or data as
defined by the Phase Compare, Data Compare, and
True/False bit fields.
If the comparisons are true, it loads the DMA SCRIPTS
Pointer (DSP) register with the contents of the DMA
SCRIPTS Pointer Save (DSPS) register and that address
value becomes the address of the next instruction.
When the LSI53C875A executes a Call instruction, the
instruction pointer contained in the DSP register is stored
in the Temporary (TEMP) register. Since the TEMP
register is not a stack and can only hold one Dword,
nested call instructions are not allowed.
If the comparisons are false, the LSI53C875A fetches the
next instruction from the address pointed to by the DSP
register and the instruction pointer is not modified.
Return Instruction
The LSI53C875A can do a true/false comparison of the
ALU carry bit, or compare the phase and/or data as
defined by the Phase Compare, Data Compare, and
True/False bit fields.
If the comparisons are true, it loads the DMA SCRIPTS
Pointer (DSP) register with the contents of the DMA
SCRIPTS Pointer Save (DSPS) register. That address
value becomes the address of the next instruction.
When a Return instruction is executed, the value stored
in the Temporary (TEMP) register is returned to the DSP
register. The LSI53C875A does not check to see whether
the Call instruction has already been executed. It does
not generate an interrupt if a Return instruction is
executed without previously executing a Call instruction.

Transfer Control Instructions

5-27

If the comparisons are false, the LSI53C875A fetches the
next instruction from the address pointed to by the DSP
register and the instruction pointer is not modified.
Interrupt Instruction
The LSI53C875A can do a true/false comparison of the
ALU carry bit, or compare the phase and/or data as
defined by the Phase Compare, Data Compare, and
True/False bit fields.
If the comparisons are true, the LSI53C875A generates
an interrupt by asserting the IRQ/ signal.
The 32-bit address field stored in the DMA SCRIPTS
Pointer Save (DSPS) register can contain a unique
interrupt service vector. When servicing the interrupt, this
unique status code allows the Interrupt Service Routine
to quickly identify the point at which the interrupt
occurred.
The LSI53C875A halts and the DMA SCRIPTS Pointer
(DSP) register must be written to before starting any
further operation.
Interrupt-on-the-Fly Instruction
The LSI53C875A can do a true/false comparison of the
ALU carry bit or compare the phase and/or data as
defined by the Phase Compare, Data Compare, and
True/False bit fields. If the comparisons are true, and the
Interrupt-on-the-Fly bit (Interrupt Status One (ISTAT1)
bit 2) is set, the LSI53C875A asserts the Interrupt-on-theFly bit.
SCSIP[2:0]

5-28

SCSI Phase
[26:24]
This 3-bit field corresponds to the three SCSI bus phase
signals that are compared with the phase lines latched
when SREQ/ is asserted. Comparisons can be performed
to determine the SCSI phase actually being driven on the
SCSI bus. Table 5.5 describes the possible combinations
and their corresponding SCSI phase. These bits are only
valid when the LSI53C875A is operating in Initiator mode.
Clear these bits when the LSI53C875A is operating in
Target mode.

SCSI SCRIPTS Instruction Set

Table 5.5

SCSI Phase Comparisons

MSG

C/D

I/O

SCSI Phase

Data-Out

Data-In

Command

Status

Reserved

Message-Out

Message-In

Relative Addressing Mode
23
When this bit is set, the 24-bit signed value in the DMA
SCRIPTS Pointer Save (DSPS) register is used as a
relative offset from the current DMA SCRIPTS Pointer
(DSP) address (which is pointing to the next instruction,
not the one currently executing). The relative mode does
not apply to Return and Interrupt SCRIPTS.
Jump/Call an Absolute Address
Start execution at the new absolute address.
Command

Condition Codes
Absolute Alternate Address

Jump/Call a Relative Address
Start execution at the current address plus (or minus) the
relative offset.
Command

Condition Codes

Don’t Care

Alternate Jump Offset

The SCRIPTS program counter is a 32-bit value pointing
to the SCRIPTS currently under execution by the
LSI53C875A. The next address is formed by adding the
32-bit program counter to the 24-bit signed value of the
last 24 bits of the Jump or Call instruction. Because it is

Transfer Control Instructions

5-29

signed (2’s complement), the jump can be forward or
backward.
A relative transfer can be to any address within a
16 Mbyte segment. The program counter is combined
with the 24-bit signed offset (using addition or
subtraction) to form the new execution address.
SCRIPTS programs may contain a mixture of direct
jumps and relative jumps to provide maximum versatility
when writing SCRIPTS. For example, major sections of
code can be accessed with far calls using the 32-bit
physical address, then local labels can be called using
relative transfers. If a SCRIPT is written using only
relative transfers it does not require any run time
alteration of physical addresses, and can be stored in and
executed from a PROM.

5-30

Reserved

Carry Test
21
When this bit is set, decisions based on the ALU carry bit
can be made. True/False comparisons are legal, but Data
Compare and Phase Compare are illegal.

Interrupt-on-the-Fly
20
When this bit is set, the interrupt instruction does not halt
the SCRIPTS processor. Once the interrupt occurs, the
Interrupt-on-the-Fly bit (Interrupt Status One (ISTAT1)
bit 2) is asserted.

JMP

Jump If True/False
19
This bit determines whether the LSI53C875A branches
when a comparison is true or when a comparison is false.
This bit applies to phase compares, data compares, and
carry tests. If both the Phase Compare and Data
Compare bits are set, then both compares must be true
to branch on a true condition. Both compares must be
false to branch on a false condition.

SCSI SCRIPTS Instruction Set

Bit 19

Result of
Compare

False

Jump Taken

True

No Jump

False

No Jump

True

Jump Taken

Action

Compare Data
18
When this bit is set, the first byte received from the SCSI
data bus (contained in the SCSI First Byte Received
(SFBR) register) is compared with the Data to be
Compared Field in the Transfer Control instruction. The
Wait for Valid Phase bit controls when this compare
occurs. The Jump if True/False bit determines the
condition (true or false) to branch on.

Compare Phase
17
When the LSI53C875A is in Initiator mode, this bit
controls phase compare operations. When this bit is set,
the SCSI phase signals (latched by SREQ/) are
compared to the Phase Field in the Transfer Control
instruction. If they match, the comparison is true. The
Wait for Valid Phase bit controls when the compare
occurs. When the LSI53C875A is operating in Target
mode and this bit is set it tests for an active SCSI SATN/
signal.

WVP

Wait for Valid Phase
16
If the Wait for Valid Phase bit is set, the LSI53C875A
waits for a previously unserviced phase before comparing
the SCSI phase and data.
If the Wait for Valid Phase bit is cleared, the LSI53C875A
compares the SCSI phase and data immediately.

DCM

Data Compare Mask
[15:8]
The Data Compare Mask allows a SCRIPT to test certain
bits within a data byte. During the data compare, if any
mask bits are set, the corresponding bit in the SCSI First
Byte Received (SFBR) data byte is ignored. For instance,
a mask of 0b01111111 and data compare value of
0b1XXXXXXX allows the SCRIPTS processor to
determine whether or not the high order bit is set while
ignoring the remaining bits.

Transfer Control Instructions

5-31

DCV

Data Compare Value
[7:0]
This 8-bit field is the data compared against the register.
These bits are used in conjunction with the Data
Compare Mask Field to test for a particular data value.

5.6.2 Second Dword
31

0
DMA SCRIPTS Pointer Save (DSPS) Register

Jump Address
[31:0]
This 32-bit field contains the address of the next
instruction to fetch when a jump is taken. Once the
LSI53C875A fetches the instruction from the address
pointed to by these 32 bits, this address is incremented
by 4, loaded into the DMA SCRIPTS Pointer (DSP)
register and becomes the current instruction pointer.

5.7 Memory Move Instructions
For Memory Move instructions, bits 5 and 4 (SIOM and DIOM) in the
DMA Mode (DMODE) register determine whether the source or
destination addresses reside in memory or I/O space. By setting these
bits appropriately, data may be moved within memory space, within I/O
space, or between the two address spaces.
The Memory Move instruction is used to copy the specified number of
bytes from the source address to the destination address.
Allowing the LSI53C875A to perform memory moves frees the system
processor for other tasks and moves data at higher speeds than available
from current DMA controllers. Up to 16 Mbytes may be transferred with
one instruction. There are two restrictions:

•

5-32

Both the source and destination addresses must start with the same
address alignment A[1:0]. If the source and destination are not
aligned, then an illegal instruction interrupt occurs. For the PCI
Cache Line Size register setting to take effect, the source and
destination must be the same distance from a cache line boundary.

SCSI SCRIPTS Instruction Set

•

Indirect addresses are not allowed. A burst of data is fetched from
the source address, put into the DMA FIFO and then written out to
the destination address. The move continues until the byte count
decrements to zero, then another SCRIPTS is fetched from system
memory.

The DMA SCRIPTS Pointer Save (DSPS) and Data Structure Address
(DSA) registers are additional holding registers used during the Memory
Move. However, the contents of the Data Structure Address (DSA)
register are preserved.

5.7.1 First Dword
31

29 28

25 24 23

DMA Command (DCMD) Register
R

IT[2:0]
1

DMA Byte Counter (DBC) Register

NF
0

Transfer Counter (TC) [23:0]
x

IT[2:0]

Instruction Type - Memory Move
[31:29]
The IT bit configuration (110) defines a Memory Move
Instruction Type.

Reserved
[28:25]
These bits are reserved and must be zero. If any of these
bits are set, an illegal instruction interrupt occurs.

No Flush
24
When this bit is set, the LSI53C875A performs a Memory
Move without flushing the prefetch unit. When this bit is
cleared, the Memory Move instruction automatically
flushes the prefetch unit. Use the No Flush option if the
source and destination are not within four instructions of
the current Memory Move instruction.
Note:

TC[23:0]

This bit has no effect unless the Prefetch Enable bit in the
DMA Control (DCNTL) register is set. For information on
SCRIPTS instruction prefetching, see Chapter 2.
Transfer Counter
[23:0]
The number of bytes to transfer is stored in the lower
24 bits of the first instruction word.

Memory Move Instructions

5-33

5.7.2 Read/Write System Memory from SCRIPTS
By using the Memory Move instruction, single or multiple register values
are transferred to or from system memory.
Because the LSI53C875A responds to addresses as defined in the Base
Address Register Zero (I/O) or Base Address Register One (MEMORY)
registers, it can be accessed during a Memory Move operation if the
source or destination address decodes to within the chip’s register space.
If this occurs, the register indicated by the lower seven bits of the address
is taken as the data source or destination. In this way, register values are
saved to system memory and later restored, and SCRIPTS can make
decisions based on data values in system memory.
The SFBR is not writable using the CPU, and therefore not by a Memory
Move. However, it can be loaded using SCRIPTS Read/Write operations.
To load the SFBR with a byte stored in system memory, first move the
byte to an intermediate LSI53C875A register (for example, a SCRATCH
register), and then to the SFBR.
The same address alignment restrictions apply to register access
operations as to normal memory-to-memory transfers.

5.7.3 Second Dword
-

0
DMA SCRIPTS Pointer Save (DSPS) Register

DSPS Register
[31:0]
These bits contain the source address of the Memory
Move.

5-34

SCSI SCRIPTS Instruction Set

5.7.4 Third Dword
31

0
Temporary (TEMP) Register

TEMP Register
[31:0]
These bits contain the destination address for the
Memory Move.

5.8 Load and Store Instructions
The Load and Store instructions provide a more efficient way to move
data from/to memory to/from an internal register in the chip without using
the normal memory move instruction.
The Load and Store instructions are represented by two Dword opcodes.
The first Dword contains the DMA Command (DCMD) and DMA Byte
Counter (DBC) register values. The second Dword contains the DMA
SCRIPTS Pointer Save (DSPS) value. This is either the actual memory
location of where to Load and Store, or the offset from the Data Structure
Address (DSA), depending on the value of bit 28 (DSA Relative).
A maximum of 4 bytes may be moved with these instructions. The
register address and memory address must have the same byte
alignment, and the count set such that it does not cross Dword
boundaries. The memory address may not map back to the chip,
excluding RAM and ROM. If it does, a PCI read/write cycle occurs (the
data does not actually transfer to/from the chip), and the chip issues an
interrupt (Illegal Instruction Detected) immediately following.

Bit A1

Bit A0

Number of Bytes Allowed to Load and Store

One, two, three or four

One, two, or three

One or two

One

Load and Store Instructions

5-35

The SIOM and DIOM bits in the DMA Mode (DMODE) register determine
whether the destination or source address of the instruction is in Memory
space or I/O space, as illustrated in the following table. The Load and
Store utilizes the PCI commands for I/O read and I/O write to access the
I/O space.
Bit

Source

Destination

SIOM (Load)

Memory

DIOM (Store)

Memory

5.8.1 First Dword
31

27 26 25 24 23 22

16 15

DMA Command (DCMD)
Register
IT[2:0]
1

5-36

DSA
x

R
0

DMA Byte Counter (DBC) Register

NF LS R
0

RA[6:0]
x

R
x

BC
0

IT[2:0]

Instruction Type
[31:29]
These bits should be 0b111, indicating the Load and
Store instruction.

DSA

DSA Relative
28
When this bit is cleared, the value in the DMA SCRIPTS
Pointer Save (DSPS) is the actual 32-bit memory address
used to perform the Load and Store to/from. When this
bit is set, the chip determines the memory address to
perform the Load and Store to/from by adding the 24-bit
signed offset value in the DMA SCRIPTS Pointer Save
(DSPS) to the Data Structure Address (DSA).

Reserved

No Flush (Store instruction only)
25
When this bit is set, the LSI53C875A performs a Store
without flushing the prefetch unit. When this bit is cleared,
the Store instruction automatically flushes the prefetch
unit. Use No Flush if the source and destination are not
within four instructions of the current Store instruction.
This bit has no effect on the Load instruction.

SCSI SCRIPTS Instruction Set

[27:26]

Note:

This bit has no effect unless the Prefetch Enable bit in the
DMA Control (DCNTL) register is set.

Load and Store
24
When this bit is set, the instruction is a Load. When
cleared, it is a Store.

Reserved

RA[6:0]

Reserved

Byte Count
[2:0]
This value is the number of bytes to Load and Store.

[15:3]

5.8.2 Second Dword
31

0
DMA SCRIPTS Pointer Save (DSPS) Register - Memory I/O Address/DSA Offset

Memory I/O Address / DSA Offset
[31:0]
This is the actual memory location of where to Load and
Store, or the offset from the Data Structure Address
(DSA) register value.

Load and Store Instructions

5-37

5-38

SCSI SCRIPTS Instruction Set

Chapter 6
Electrical
Specifications
This section specifies the LSI53C875A electrical and mechanical
characteristics. It is divided into the following sections:

•

Section 6.1, “DC Characteristics”

•

Section 6.2, “TolerANT Technology Electrical Characteristics”

•

Section 6.3, “AC Characteristics”

•

Section 6.4, “PCI and External Memory Interface Timing Diagrams”

•

Section 6.5, “SCSI Timing Diagrams”

•

Section 6.6, “Package Diagrams”

6.1 DC Characteristics
This section of the manual describes the LSI53C875A DC
characteristics. Table 6.1 through Table 6.10 give current and voltage
specifications.

LSI53C875A PCI to Ultra SCSI Controller

6-1

Table 6.1
Symbol

Absolute Maximum Stress Ratings1
Parameter

Min

Max

Unit

Test Conditions

TSTG

Storage temperature

−55

150

°C

–

VDD

Supply voltage

−0.5

4.5

–

VIN

Input voltage

VSS −0.3

5.55

SCSI 5 V TolerANT pads

ILP2

Latch-up current

±=150

–

ESD

Electrostatic discharge

–

MIL-STD 883C,
Method 3015.7

1. Stresses beyond those listed above may cause permanent damage to the device. These are stress
ratings only; functional operation of the device at these or any other conditions beyond those
indicated in the Operating Conditions section of the manual is not implied.
2. −2 V < VPIN < 8 V.

Table 6.2
Symbol

Operating Conditions1
Parameter

Min

Max

Unit

Test Conditions

VDD

Supply voltage

2.97

3.63

±10%

IDD

Supply current (dynamic)
Supply current (static)

–
–

200 mA
1 mA

mA
mA

–
–

Operating free air

°C

–

Thermal resistance
(junction to ambient air)

–

25.1
34.7

°C/W

160 PQFP
169 PBGA

θJA

1. Conditions that exceed the operating limits may cause the device to function incorrectly.

Table 6.3
Symbol
CI
CIO

6-2

Input Capacitance
Parameter

Min

Max

Unit

Test Conditions

Input capacitance of input pads

–

Input capacitance of I/O pads

–

Electrical Specifications

Table 6.4
Symbol

Bidirectional Signals—MAD[7:0], MAS/[1:0], MCE/, MOE/, MWE/
Parameter

Min

Max

Unit

Test Conditions

VIH

Input high voltage

2.0

5.25

–

VIL

Input low voltage

VSS −0.5

0.8

–

VOH

Output high voltage

2.4

VDD

−4 mA

VOL

Output low voltage

VSS

0.4

4 mA

IOZ

3-state leakage

−10

µA

–

Pull-down current

12.5

+50

µA

–

IPULL

Table 6.5
Symbol

Bidirectional Signals—GPIO0_FETCH/, GPIO1_MASTER/, GPIO[2:4]
Parameter

Min

Max

Unit

Test Conditions

VIH

Input high voltage

2.0

5.25

–

VIL

Input low voltage

VSS −0.5

0.8

–

VOH

Output high voltage

2.4

VDD

−8 mA

VOL

Output low voltage

VSS

0.4

8 mA

IOZ

3-state leakage

−10

µA

–

Pull-down current

12.5

+50

µA

–

IPULL

DC Characteristics

6-3

Table 6.6

Bidirectional Signals—AD[31:0], C_BE[3:0]/, FRAME/, IRDY/, TRDY/,
DEVSEL/, STOP/, PERR/, PAR

Symbol Parameter

Min

Max

Unit

Test Conditions

VIH

Input high voltage

0.5 VDD

5.25

–

VIL

Input low voltage

VSS

0.3 VDD

–

VOH

Output high voltage

0.9 VDD

VDD

−16 mA

VOL

Output low voltage

VSS

0.1 VDD

16 mA

IOZ

3-state leakage

−10

µA

–

Pull-down current

–

µA

–

IPULL

Table 6.7

Input Signals—CLK, GNT/, IDSEL, RST/, SCLK, TCK, TDI, TEST_HSC,
TEST_RST, TMS, TRST/

Symbol Parameter

Max

Unit

Test Conditions

VIH

Input high voltage

0.5 VDD

5.25

–

VIL

Input low voltage

VSS

0.3 VDD

–

IIN

Input leakage

−10

µA

–

Pull-up current - only on
TCK, TDI, TEST_HSC,
TEST_RST, TMS, TRST/

−50

−12.5

µA

–

IPULL

Table 6.8
Symbol

6-4

Min

Output Signal—TDO
Parameter

Min

Max

Unit

Test Conditions

VOH

Output high voltage

2.4

VDD

−4 mA

VOL

Output low voltage

VSS

0.4

4 mA

IOZ

3-state leakage

−10

µA

–

Electrical Specifications

Table 6.9
Symbol

Output Signals—IRQ/, MAC/_TESTOUT, REQ/
Parameter

Min

Max

Unit

Test Conditions

VOH

Output high voltage

0.9 VDD

VDD

−16 mA

VOL

Output low voltage

VSS

0.1 VDD

16 mA

IOZ

3-state leakage

−10

µA

–

Pull-down current - only
on IRQ/

−50

−12.5

µA

–

Parameter

Min

Max

Unit

Test Conditions

VOL

Output low voltage

VSS

0.1 VDD

16 mA

IOZ

3-state leakage

−10

µA

–

IPULL

Table 6.10
Symbol

Output Signal—SERR/

6.2 TolerANT Technology Electrical Characteristics
The LSI53C875A features TolerANT technology, which includes active
negation on the SCSI drivers and input signal filtering on the SCSI
receivers. Active negation actively drives the SCSI Request,
Acknowledge, Data, and Parity signals HIGH rather than allowing them
to be passively pulled up by terminators. Table 6.11 provides electrical
characteristics for SE SCSI signals. Figure 6.1 through Figure 6.5
provide reference information for testing SCSI signals.

TolerANT Technology Electrical Characteristics

6-5

Table 6.11
Symbol

TolerANT Technology Electrical Characteristics for SE SCSI Signals

Parameter

Min1

Max

Unit

Test Conditions

VOH2

Output high voltage

2.0

VDD +0.3

IOH = 7 mA

VOL

Output low voltage

VSS

0.5

IOL = 48 mA

VIH

Input high voltage

2.0

VDD +0.3

–

VIL

Input low voltage

VSS −0.3

0.8

Referenced to VSS

VIK

Input clamp voltage

−0.66

−0.77

VDD = 4.75; II = −20 mA

VTH

Threshold, HIGH to LOW

1.0

1.2

–

VTL

Threshold, LOW to HIGH

1.4

1.6

–

300

500

–

VTH–VTL Hysteresis
IOH

Output high current

2.5

VOH = 2.5 V

Output low current

100

200

VOL = 0.5 V

Short-circuit output high current

–

625

Output driving low, pin
shorted to VDD supply3

IOSL

Short-circuit output low current

–

Output driving high, pin
shorted to VSS supply

ILH

Input high leakage

–

µA

−0.5 < VDD < 5.25
VPIN = 2.7 V

ILL

Input low leakage

–

−20

µA

−0.5 < VDD < 5.25
VPIN = 0.5 V

Input resistance

–

MΩ

SCSI pins

Capacitance per pin

–

PQFP

Rise time, 10% to 90%

4.0

18.5

Figure 6.1

Fall time, 90% to 10%

4.0

18.5

Figure 6.1

dVH/dt

Slew rate, LOW to HIGH

0.15

0.50

V/ns

Figure 6.1

dVL/dt

Slew rate, HIGH to LOW

0.15

0.50

V/ns

Figure 6.1

–

MIL-STD-883C; 3015-7

IOL
IOSH

ESD

Electrostatic discharge
Latch-up

100

–

Filter delay

Figure 6.2

Ultra filter delay

Figure 6.2

Extended filter delay

Figure 6.2

1. These values are guaranteed by periodic characterization; they are not 100% tested on every
device.
2. Active negation outputs only: Data, Parity, SREQ/, SACK/.
3. Single pin only; irreversible damage may occur if sustained for one second.

6-6

Electrical Specifications

Figure 6.1

Rise and Fall Time Test Condition
47 Ω

20 pF

−

Figure 6.2

2.5 V

SCSI Input Filtering
t1

REQ/ or SACK/ Input

VTH

Note: t1 is the input filtering period.

Figure 6.3

Hysteresis of SCSI Receivers

Received Logic Level

1.1

1.3

0
1.5

1.7

Input Voltage (Volts)

TolerANT Technology Electrical Characteristics

6-7

Figure 6.4

Input Current as a Function of Input Voltage

+40

Input Current (milliAmperes)

+20
14.4 V
8.2 V
0

−0.7 V
HIGH-Z

OUTPUT

−20

ACTIVE

−40
−4

Input Voltage (Volts)

Figure 6.5

Output Current as a Function of Output Voltage
100
Output Source Current (milliAmperes)

Output Sink Current (milliAmperes)

−200

−400

−600

−800
0

Output Voltage (Volts)

6-8

Electrical Specifications

0
0

Output Voltage (Volts)

6.3 AC Characteristics
The AC characteristics described in this section apply over the entire
range of operating conditions (refer to the DC Characteristics section).
Chip timings are based on simulation at worst case voltage, temperature,
and processing. Timing was developed with a load capacitance of 50 pF.
Table 6.12 and Figure 6.6 provide external clock timing data.

Table 6.12
Symbol
t1

External Clock1
Parameter

Min

Max

Unit

SCSI clock cycle time (SCLK)

CLK LOW time3

–

SCLK LOW time3

CLK HIGH time3

–

CLK slew rate

–

V/ns

SCLK slew rate

–

V/ns

Bus clock cycle time
2

SCLK HIGH time
t4

1. Timings are for an external 40 MHz clock.
2. This parameter must be met to ensure SCSI timings are within specification.
3. Duty cycle not to exceed 60/40.

Figure 6.6

External Clock
t1
t3

CLK, SCLK 1.4 V
t4

AC Characteristics

6-9

Table 6.13 and Figure 6.7 provide Reset Input timing data.
Table 6.13
Symbol

Reset Input
Parameter

Min

Max

Unit

Reset pulse width

–

tCLK

Reset deasserted setup to CLK HIGH

–

MAD setup time to CLK HIGH
(for configuring the MAD bus only)

–

MAD hold time from CLK HIGH
(for configuring the MAD bus only)

–

Figure 6.7

Reset Input

CLK
t1

RST/
t3
MAD1

Valid Data
Note:
1. When enabled.

Table 6.14 and Figure 6.8 provide Interrupt Output timing data.
Table 6.14
Symbol

6-10

Interrupt Output
Parameter

Min

Max

Unit

CLK HIGH to IRQ/ LOW

CLK HIGH to IRQ/ HIGH

IRQ/ deassertion time

–

CLK

Electrical Specifications

Figure 6.8

Interrupt Output
t2

IRQ/

CLK

6.4 PCI and External Memory Interface Timing Diagrams
Figure 6.9 through Figure 6.32 represent signal activity when the
LSI53C875A accesses the PCI bus. This section includes timing
diagrams for access to three groups of memory configurations. The first
group applies to Target Timing. The second group applies to Initiator
Timing. The third group applies to External Memory Timing.
Note:

Multiple byte accesses to the external memory bus
increase the read or write cycle by 11 clocks for each
additional byte.

Timing diagrams included in this section are:

•

Target Timing
–

PCI Configuration Register Read

–

PCI Configuration Register Write

–

32-Bit Operating Register/SCRIPTS RAM Read

–

64-Bit Address Operating Register/SCRIPTS RAM Read

–

32-Bit Operating Register/SCRIPTS RAM Write

–

64-Bit Address Operating Register/SCRIPTS RAM Write

Initiator Timing
–

Nonburst Opcode Fetch, 32-Bit Address and Data

–

Burst Opcode Fetch, 32-Bit Address and Data

–

Back-to-Back Read, 32-Bit Address and Data

–

Back-to-Back Write, 32-Bit Address and Data

PCI and External Memory Interface Timing Diagrams

6-11

•

6-12

–

Burst Read, 32-Bit Address and Data

–

Burst Read, 64-Bit Address and Data

–

Burst Write, 32-Bit Address and Data

–

Burst Write, 64-Bit Address and 32-Bit Data

External Memory Timing
–

External Memory Read

–

External Memory Write

–

Normal/Fast Memory (≥ 128 Kbytes) Single Byte Access Read
Cycle

–

Normal/Fast Memory (≥ 128 Kbytes) Single Byte Access Write
Cycle

–

Nornal/Fast Memory (≥ 128 Kbytes) Multiple Byte Access Read
Cycle

–

Normal/Fast Memory (≥ 128 Kbytes) Multiple Byte Access Write
Cycle

–

Slow Memory (≥ 128 Kbytes) Read Cycle

–

Slow Memory (≥ 128 Kbytes) Write Cycle

–

≤ 64 Kbytes ROM Read Cycle

–

≤ 64 Kbyte ROM Write Cycle

Electrical Specifications

6.4.1 Target Timing
The tables and figures in this section describe target timings.
Table 6.15
Symbol

PCI Configuration Register Read
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

–

Figure 6.9

PCI Configuration Register Read

CLK
(Driven by System)
t1
FRAME/
(Driven by System)
t1

AD
(Driven by Master-Addr;
LSI53C875A-Data)

Data Out
t2

t1
C_BE/
(Driven by Master)
PAR
(Driven by Master-Addr;
LSI53C875A-Data)

Addr
In

CMD

Byte Enable

t1
In

Out
t2

t2
IRDY/
(Driven by Master)
t1
TRDY/
(Driven by LSI53C875A)
t3
STOP/
(Driven by LSI53C875A)
DEVSEL/
(Driven by LSI53C875A)
t1

IDSEL
(Driven by Master)
t2

PCI and External Memory Interface Timing Diagrams

6-13

Table 6.16
Symbol

PCI Configuration Register Write
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

–

Figure 6.10 PCI Configuration Register Write
CLK
(Driven by System)
t1
FRAME/
(Driven by Master)
t1

Addr
In

AD
(Driven by Master)
t2
C_BE/
(Driven by Master)

t1
Data In

t1
CMD

Byte Enable

PAR
(Driven by Master)
t1

IRDY/
(Driven by Master)
TRDY/
(Driven by LSI53C875A)
t3
STOP/
(Driven by LSI53C875A)
DEVSEL/
(Driven by LSI53C875A)
t3

t1
IDSEL
(Driven by Master)
t2

6-14

Electrical Specifications

Table 6.17
Symbol

32-Bit Operating Register/SCRIPTS RAM Read
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

–

Figure 6.11 32-Bit Operating Register/SCRIPTS RAM Read
CLK
(Driven by System)
t2

FRAME/
(Driven by Master)
t3
AD
(Driven by Master-Addr;
LSI53C875A-Data)

Data
Out

Addr
In

C_BE/
(Driven by Master)

t1
CMD

Byte Enable

t2
PAR
(Driven by Master-Addr;
LSI53C875A-Data)

t1
In
t2

t3
Out

IRDY/
(Driven by Master)
t3
TRDY/
(Driven by LSI53C875A)

STOP/
(Driven by LSI53C875A)

DEVSEL/
(Driven by LSI53C875A)
t3

PCI and External Memory Interface Timing Diagrams

6-15

Table 6.18
Symbol

64-Bit Address Operating Register/SCRIPTS RAM Read
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

–

Figure 6.12 64-Bit Address Operating Register/SCRIPTS RAM Read
CLK
(Driven by System)
t1
FRAME/
(Driven by Master)
AD[31:0]
(Driven by Master-Addr;
LSI53C875A-Data)
C_BE[3:0]
(Driven by Master)
PAR
(Driven by Master-Addr;
LSI53C875A-Data)
IRDY/
(Driven by Master)

t1
Addr
Lo

Addr
Hi

t1
Dual
Addr

Bus
CMD

Data
Out
t1
Byte Enable
t2

t1
In

In
t2

Out
t2

t3
TRDY/
(Driven by LSI53C875A)

t3
STOP/
(Driven by LSI53C875A)

t3
DEVSEL/
(Driven by LSI53C875A)

6-16

Electrical Specifications

Table 6.19
Symbol

32-Bit Operating Register/SCRIPTS RAM Write
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

–

Figure 6.13 32-Bit Operating Register/SCRIPTS RAM Write
CLK
(Driven by System)
t1

FRAME/
(Driven by Master)
t1
AD
(Driven by Master)

Addr
In

t1
C_BE/
(Driven by Master)

CMD
t2

PAR
(Driven by Master)

t1
In

In
t2

IRDY/
(Driven by Master)
t1

TRDY/
(Driven by LSI53C875A)

STOP/
(Driven by LSI53C875A)

t3
DEVSEL/
(Driven by LSI53C875A)

PCI and External Memory Interface Timing Diagrams

6-17

Table 6.20
Symbol

64-Bit Address Operating Register/SCRIPTS RAM Write
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

–

Figure 6.14 64-Bit Address Operating Register/SCRIPTS RAM Write
CLK
(Driven by System)
t1

FRAME/
(Driven by Master)
t1

t1
AD
(Driven by Master)
t2
C_BE/
(Driven by Master)
t2
PAR
(Driven by Master)

Addr
Lo

Addr
Hi

t1
Dual
Addr

Bus
CMD

t2
Data In

t1
Byte Enable
t2

t1
In

IRDY/
(Driven by Master)
t3
TRDY/
(Driven by LSI53C875A)
STOP/
(Driven by LSI53C875A)
t3
DEVSEL/
(Driven by LSI53C875A)

6-18

Electrical Specifications

6.4.2 Initiator Timing
The tables and figures in this section describe LSI53C875A initiator
timings.
Table 6.21
Symbol

Nonburst Opcode Fetch, 32-Bit Address and Data
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

Side signal input setup time

–

Side signal input hold time

–

CLK to side signal output valid

CLK HIGH to GPIO0_FETCH/ LOW

–

CLK HIGH to GPIO0_FETCH/ HIGH

–

CLK HIGh to GPIO1_MASTER/ LOW

–

t10

CLK HIGH to GPIO1_MASTER/ HIGH

–

PCI and External Memory Interface Timing Diagrams

6-19

Figure 6.15 Nonburst Opcode Fetch, 32-Bit Address and Data
CLK
(Driven by System)
t7

GPIO0_FETCH/
(Driven by LSI53C875A)
t9

t10

GPIO1_MASTER/
(Driven by LSI53C875A)
t6
REQ/
(Driven by LSI53C875A)
t4
GNT/
(Driven by Arbiter)
t5
FRAME/
(Driven by LSI53C875A)

AD
(Driven by LSI53C875AAddr; Target-Data)

Data
In

Addr
Out

Data
In
t2

t3
C_BE/
(Driven by LSI53C875A)
PAR
(Driven by LSI53C875AAddr/ Target-Data)

CMD

IRDY/
(Driven by LSI53C875A)
t3

TRDY/
(Driven by Target)
t2
STOP/
(Driven by Target)
t1
DEVSEL/
(Driven by Target)

6-20

Electrical Specifications

Table 6.22
Symbol

Burst Opcode Fetch, 32-Bit Address and Data
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

Side signal input setup time

–

Side signal input hold time

–

CLK to side signal output valid

CLK HIGH to GPIO0_FETCH/ LOW

–

CLK HIGH to GPIO0_FETCH/ HIGH

–

CLK HIGH to GPIO1_MASTER/ LOW

–

t10

CLK HIGH to GPIO1_MASTER/ HIGH

–

PCI and External Memory Interface Timing Diagrams

6-21

Figure 6.16 Burst Opcode Fetch, 32-Bit Address and Data
CLK
(Driven by System)
t7

GPIO0_FETCH/
(Driven by LSI53C875A)
t10

t9
GPIO1_MASTER/
(Driven by LSI53C875A)
t6
REQ/
(Driven by LSI53C875A)
t4
GNT/
(Driven by Arbiter)
t5
FRAME/
(Driven by LSI53C875A)
AD
(Driven by LSI53C875AAddr; Target-Data)

Data
In

Addr
Out
t1

t3
C_BE/
(Driven by LSI53C875A)

CMD
t3

BE
t1

PAR
(Driven by LSI53C875AAddr/ Target-Data)

Out

In
t2

t3
IRDY/
(Driven by LSI53C875A)
t3

TRDY/
(Driven by Target)
t2
STOP/
(Driven by Target)
t1
DEVSEL/
(Driven by Target)

6-22

Electrical Specifications

Table 6.23
Symbol

Back-to-Back Read, 32-Bit Address and Data
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

Side signal input setup time

–

Side signal input hold time

–

CLK to side signal output valid

CLK HIGH to GPIO1_MASTER/ LOW

–

t10

CLK HIGH to GPIO1_MASTER/ HIGH

–

PCI and External Memory Interface Timing Diagrams

6-23

Figure 6.17 Back-to-Back Read, 32-Bit Address and Data
CLK
(Driven by System)

GPIO0_FETCH/
(Driven by LSI53C875A)

t10

GPIO1_MASTER/
(Driven by LSI53C875A)

REQ/
(Driven by LSI53C875A)

GNT/
(Driven by Arbiter)
t4

FRAME/
(Driven by LSI53C875A)

Data In

C_BE/
(Driven by LSI53C875A)

PAR

t2
CMD

CMD

(Driven by LSI53C875AAddr; Target-Data)

t1
In

Out

IRDY/
(Driven by LSI53C875A)

t1
TRDY/
(Driven by Target)
t2
STOP/
(Driven by Target)
t1
DEVSEL/
(Driven by Target)
t2

6-24

Data In
Addr
Out

Addr
Out

(Driven by LSI53C875AAddr; Target-Data)

Electrical Specifications

Table 6.24
Symbol

Back-to-Back Write, 32-Bit Address and Data
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

Side signal input setup time

–

Side signal input hold time

–

CLK to side signal output valid

CLK HIGH to GPIO1_MASTER/ LOW

–

t10

CLK HIGH to GPIO1_MASTER/ HIGH

–

PCI and External Memory Interface Timing Diagrams

6-25

Figure 6.18 Back-to-Back Write, 32-Bit Address and Data
CLK
(Driven by System)

GPIO0_FETCH/
(Driven by LSI53C875A)
t9

t10

GPIO1_MASTER/
(Driven by LSI53C875A)
t6
REQ/
(Driven by LSI53C875A)
t4
GNT/
(Driven by Arbiter)

FRAME/
(Driven by LSI53C875A)
AD
(Driven by LSI53C875AAddr; Target-Data)

t5
t3

t3
Addr Data
Out Out

t3
C_BE/
(Driven by LSI53C875A)

Addr Data
Out Out

CMD

PAR
(Driven by LSI53C875AAddr; Target-Data)

CMD

t3
IRDY/
(Driven by LSI53C875A)
t1
TRDY/
(Driven by Target)
t2
STOP/
(Driven by Target)
t1
DEVSEL/
(Driven by Target)

6-26

Electrical Specifications

Table 6.25
Symbol

Burst Read, 32-Bit Address and Data
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

PCI and External Memory Interface Timing Diagrams

6-27

Figure 6.19 Burst Read, 32-Bit Address and Data
CLK

GPIO0_FETCH/
(Driven by LSI53C875A)
GPIO1_MASTER/
(Driven by LSI53C875A)

REQ/
(Driven by LSI53C875A)
GNT/
(Driven by Arbiter)

FRAME/
(Driven by LSI53C875A)
Data In
AD
(Driven by LSI53C875AAddr; Target-Data)

Addr
Out
t3

C_BE/
(Driven by LSI53C875A)

CMD

PAR
(Driven by LSI53C875AAddr; Target-Data)

Out

IRDY/
(Driven by LSI53C875A)
t1
TRDY/
(Driven by Target)
t2
STOP/
(Driven by Target)
t2
DEVSEL/
(Driven by Target)

6-28

Electrical Specifications

Table 6.26
Symbol

Burst Read, 64-Bit Address and Data
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

t10

CLK HIGH to GPIO1_MASTER/HIGH

–

PCI and External Memory Interface Timing Diagrams

6-29

Figure 6.20 Burst Read, 64-Bit Address and Data
CLK

GPIO0_FETCH/
(Driven by LSI53C875A)
t10
GPIO1_MASTER/
(Driven by LSI53C875A)
REQ/
(Driven by LSI53C875A)
GNT/
(Driven by Arbiter)

FRAME/
(Driven by LSI53C875A)
Data In
AD[31:0]
(Addr driven by LSI53C875AData driven by Target)

Addr
Out Lo

Addr
Out Hi

t3
C_BE[3:0]/
(Driven by LSI53C875A)

Dual
Addr

Bus
CMD

BE
t2

PAR
(Addr drvn by LSI53C875A;
Data drvn by Target)

Out

IRDY/
(Driven by LSI53C875A)
t1
TRDY/
(Driven by Target)
t2
STOP/
(Driven by Target)
t2
DEVSEL/
(Driven by Target)

6-30

Electrical Specifications

Table 6.27
Symbol

Burst Write, 32-Bit Address and Data
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

t10

CLK HIGH to GPIO1_MASTER/ HIGH

–

PCI and External Memory Interface Timing Diagrams

6-31

Figure 6.21 Burst Write, 32-Bit Address and Data
CLK
(Driven by System)

GPIO0_FETCH/
(Driven by LSI53C875A)
GPIO1_MASTER/
(Driven by LSI53C875A)

t10

REQ/
(Driven by LSI53C875A)
GNT/
(Driven by Arbiter)

FRAME/
(Driven by LSI53C875A)
AD
(Driven by LSI53C875A)

Addr
Out

C_BE/
(Driven by LSI53C875A)

CMD

Data
Out

t3
PAR
(Driven by LSI53C875A)

IRDY/
(Driven by LSI53C875A)
t1
TRDY/
(Driven by Target)
t2
STOP/
(Driven by Target)
t1
DEVSEL/
(Driven by Target)
t2

6-32

Electrical Specifications

Table 6.28
Symbol

Burst Write, 64-Bit Address and 32-Bit Data
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

t10

CLK HIGH to GPIO1_MASTER/ HIGH

–

PCI and External Memory Interface Timing Diagrams

6-33

Figure 6.22 Burst Write, 64-Bit Address and 32-Bit Data
CLK
(Driven by System)

GPIO0_FETCH/
(Driven by LSI53C875A)
t10
GPIO1_MASTER/
(Driven by LSI53C875A)

REQ/
(Driven by LSI53C875A)
GNT/
(Driven by Arbiter)

FRAME/
(Driven by LSI53C875A)

AD[31:0]
(Driven by LSI53C875A)

Addr
Out Lo

Addr
Out Hi

Data
Out

C_BE[3:0]/
(Driven by LSI53C875A)

Dual
Addr

Bus
CMD

PAR
(Driven by LSI53C875A)
t3
IRDY/
(Driven by LSI53C875A)
t1
TRDY/
(Driven by Target)
t2
STOP/
(Driven by Target)
t2
DEVSEL/
(Driven by Target)
t1

6-34

Electrical Specifications

6.4.3 External Memory Timing
The tables and figures in this section describe LSI53C875A external
timings. The External Memory Write timings start on page 6-40.
Table 6.29
Symbol

External Memory Read
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

–

t11

Address setup to MAS/ HIGH

–

t12

Address hold from MAS/ HIGH

–

t13

MAS/ pulse width

–

t14

MCE/ LOW to data clocked in

150

–

t15

Address valid to data clocked in

205

–

t16

MOE/ LOW to data clocked in

100

–

t17

Data hold from address, MOE/, MCE/ change

–

t19

Data setup to CLK HIGH

–

PCI and External Memory Interface Timing Diagrams

6-35

Figure 6.23 External Memory Read
1

CLK
(Driven by System)
t1

FRAME/
(Driven by Master)
AD
(Driven by Master-Addr;
LSI53C875A-Data)
C_BE[3:0]/
(Driven by Master)

Addr
In
t2
t1

PAR
(Driven by Master-Addr;
LSI53C875A-Data)

Byte Enable

CMD
t1
In
t2
t1

IRDY/
(Driven by Master)
TRDY/
(Driven by LSI53C875A)
STOP/
(Driven by LSI53C875A)
DEVSEL/
(Driven by LSI53C875A)
t3

MAD
(Addr driven by LSI53C875A;
Data driven by Memory)

Upper
Address
t11

Middle
Address
t12

MAS1/
(Driven by LSI53C875A)
t13

MAS0/
(Driven by LSI53C875A)
MCE/
(Driven by LSI53C875A)
MOE/
(Driven by LSI53C875A)
MWE/
(Driven by LSI53C875A)

6-36

Electrical Specifications

Lower
Address

Figure 6.23 External Memory Read (Cont.)
9

CLK
(Driven by System)
FRAME/
(Driven by Master)
t3

AD
(Driven by Master-Addr;
LSI53C875A-Data)

Data
Out

C_BE[3:0]/
(Driven by Master)

Byte Enable
t2
t3

PAR
(Driven by Master-Addr;
LSI53C875A-Data)

Out
t2

IRDY/
(Driven by Master)
t3

TRDY/
(Driven by LSI53C875A)
t3

STOP/
(Driven by LSI53C875A)
DEVSEL/
(Driven by LSI53C875A)
t19

MAD
(Addr driven by LSI53C875A;
Data driven by Memory)
MAS1/
(Driven by LSI53C875A)

t17

Data
In

Lower
Address

t15

MAS0/
(Driven by LSI53C875A)
t14

MCE/
(Driven by LSI53C875A)
t16

MOE/
(Driven by LSI53C875A)
MWE/
(Driven by LSI53C875A)

PCI and External Memory Interface Timing Diagrams

6-37

Table 6.30
Symbol

6-38

External Memory Write
Parameter

Min

Max

Unit

Shared signal input setup time

–

Shared signal input hold time

–

CLK to shared signal output valid

–

t11

Address setup to MAS/ HIGH

–

t12

Address hold from MAS/ HIGH

–

t13

MAS/ pulse width

–

t20

Data setup to MWE/ LOW

–

t21

Data hold from MWE/ HIGH

–

t22

MWE/ pulse width

100

–

t23

Address setup to MWE/ LOW

–

t24

MCE/ LOW to MWE/ HIGH

120

–

t25

MCE/ LOW to MWE/ LOW

–

t26

MWE/ HIGH to MCE/ HIGH

–

Electrical Specifications

The External Memory Write timings start on page 6-40.

PCI and External Memory Interface Timing Diagrams

6-39

Figure 6.24 External Memory Write
1

CLK
(Driven by System)
t1

FRAME/
(Driven by Master)

AD
(Driven by Master-Addr;
LSI53C875A-Data)

Addr
In

C_BE[3:0]/
(Driven by Master)

PAR
(Driven by Master-Addr;
LSI53C875A-Data)

Byte Enable

CMD
t1
In
t2
t1

IRDY/
(Driven by Master)
TRDY/
(Driven by LSI53C875A)
STOP/
(Driven by LSI53C875A)
DEVSEL/
(Driven by LSI53C875A)
t3

MAD
(Addr driven by LSI53C875A;
Data driven by Memory)

Higher
Address
t11

Middle
Address
t12

MAS1/
(Driven by LSI53C875A)
t13

MAS0/
(Driven by LSI53C875A)
MCE/
(Driven by LSI53C875A)
MOE/
(Driven by LSI53C875A)
MWE/
(Driven by LSI53C875A)

6-40

Electrical Specifications

Lower
Address

Figure 6.24 External Memory Write (Cont.)
9

20 21

CLK
(Driven by System)
FRAME/
(Driven by Master)
t2

AD
(Driven by Master-Addr;
LSI53C875A-Data)

Data In

C_BE[3:0]/
(Driven by Master)

Byte Enable
t2

PAR
(Driven by Master-Addr;
LSI53C875A-Data)

In
t2

IRDY/
(Driven by Master)
t3

TRDY/
(Driven by LSI53C875A)
t3

STOP/
(Driven by LSI53C875A)
DEVSEL/
(Driven by LSI53C875A)
MAD
(Addr driven by LSI53C875A;
Data driven by Memory)

Lower
Address

Data Out

MAS1/
(Driven by LSI53C875A)
MAS0/
(Driven by LSI53C875A)
t24

MCE/
(Driven by LSI53C875A)
t25

MOE/
(Driven by LSI53C875A)
t20

t21

t26

MWE/
(Driven by LSI53C875A)
t23

t22

PCI and External Memory Interface Timing Diagrams

6-41

Table 6.31
Symbol

Normal/Fast Memory (≥= 128 Kbytes) Single Byte Access Read Cycle
Parameter

Min

Max

Unit

t11

Address setup to MAS/ HIGH

–

t12

Address hold from MAS/ HIGH

–

t13

MAS/ pulse width

–

t14

MCE/ LOW to data clocked in

150

–

t15

Address valid to data clocked in

205

–

t16

MOE/ LOW to data clocked in

100

–

t17

Data hold from address, MOE/, MCE/ change

–

t18

Address out from MOE/, MCE/ HIGH

–

t19

Data setup to CLK HIGH

–

Figure 6.25 Normal/Fast Memory (≥= 128 Kbytes) Single Byte Access Read Cycle
CLK
MAD
(Addr driven by LSI53C875A;
Data driven by memory)

t19
Higher
Address
t11
t12

t17

MAS1/
(Driven by LSI53C875A)
t13

t15

MAS0/
(Driven by LSI53C875A)
t14
MCE/
(Driven by LSI53C875A)
t16

t18

MOE/
(Driven by LSI53C875A)
MWE/
(Driven by LSI53C875A)
1. Middle Address

6-42

Electrical Specifications

2. Lower Address

3. Valid Read Data

Table 6.32
Symbol

Normal/Fast Memory (≥= 128 Kbytes) Single Byte Access Write Cycle
Parameter

Min

Max

Unit

t11

Address setup to MAS/ HIGH

–

t12

Address hold from MAS/ HIGH

–

t13

MAS/ pulse width

–

t20

Data setup to MWE/ LOW

–

t21

Data hold from MWE/ HIGH

–

t22

MWE/ pulse width

100

–

t23

Address setup to MWE/ LOW

–

t24

MCE/ LOW to MWE/ HIGH

120

–

t25

MCE/ LOW to MWE/ LOW

–

t26

MWE/ HIGH to MCE/ HIGH

–

Figure 6.26 Normal/Fast Memory (≥= 128 Kbytes) Single Byte Access Write Cycle
CLK

MAD
(Driven by LSI53C875A)

Higher
Address
t11

Valid Write Data

t12

MAS1/
(Driven by LSI53C875A)
t23

t13
MAS0/
(Driven by LSI53C875A)

t24
MCE/
(Driven by LSI53C875A)
t25
MOE/
(Driven by LSI53C875A)

t20

t26
t21

t22

MWE/
(Driven by LSI53C875A)
1. Middle Address

2. Lower Address

PCI and External Memory Interface Timing Diagrams

6-43

Figure 6.27 Normal/Fast Memory (≥= 128 Kbytes) Multiple Byte Access Read Cycle
0

CLK
(Driven by System)
FRAME/
(Driven by Master)
AD
(Driven by LSI53C875AMaster-Addr; Data)

Addr In

CMD
C_BE[3:0]/
(Driven by Master)
PAR
(Driven by LSI53C875AMaster-Addr; Data)

Byte Enable

IRDY/
(Driven by Master)
TRDY/
(Driven by LSI53C875A)
STOP/
(Driven by LSI53C875A)
DEVSEL/
(Driven by LSI53C875A)
MAD
(Addr Driven by LSI53C875A;

Data driven by Memory)

Upper
Address

MAS1/
(Driven by LSI53C875A)
MAS0/
(Driven by LSI53C875A)
MCE/
(Driven by LSI53C875A)
MOE/
(Driven by LSI53C875A)
MWE/
(Driven by LSI53C875A)

6-44

Electrical Specifications

Middle
Lower
Address Address

Figure 6.27 Normal/Fast Memory (≥= 128 Kbytes) Multiple Byte Access Read Cycle
(Cont.)
15 16

CLK
(Driven by System)
FRAME/
(Driven by Master)
Data In
AD
(Driven by LSI53C875AMaster-Addr; Data)
C_BE[3:0]/
(Driven by Master)

Byte Enable

PAR
(Driven by LSI53C875AMaster-Addr; Data)

Out

IRDY/
(Driven by Master)
TRDY/
(Driven by LSI53C875A)
STOP/
(Driven by LSI53C875A)
DEVSEL/
(Driven by LSI53C875A)
MAD
(Addr Driven by LSI53C875A;

Data driven by Memory)

Data In

Data In
Lower
Address

MAS1/
(Driven by LSI53C875A)
MAS0/
(Driven by LSI53C875A)
MCE/
(Driven by LSI53C875A)

MOE/
(Driven by LSI53C875A)

MWE/
(Driven by LSI53C875A)

PCI and External Memory Interface Timing Diagrams

6-45

Figure 6.28 Normal/Fast Memory (≥= 128 Kbytes) Multiple Byte Access Write Cycle
0

CLK
(Driven by System)
FRAME/
(Driven by Master)
AD
(Driven by Master-Addr;
LSI53C875A-Data)

Addr In
Data In
CMD

C_BE[3:0]/
(Driven by Master)
PAR
(Driven by Master-Addr;
LSI53C875A-Data)

Byte Enable

IRDY/
(Driven by Master)
TRDY/
(Driven by LSI53C875A)
STOP/
(Driven by LSI53C875A)
DEVSEL/
(Driven by LSI53C875A)
MAD
(Driven by LSI53C875A)

Upper
Address

MAS1/
(Driven by LSI53C875A)
MAS0/
(Driven by LSI53C875A)
MCE/
(Driven by LSI53C875A)
MOE/
(Driven by LSI53C875A)
MWE/
(Driven by LSI53C875A)

6-46

Electrical Specifications

Middle
Address

Lower
Address

Figure 6.28 Normal/Fast Memory (≥= 128 Kbytes) Multiple Byte Access Write Cycle
(Cont.)
15 16

CLK
(Driven by System)
FRAME/
(Driven by Master)
AD
(Driven by Master-Addr;
LSI53C875A-Data)

Data In

C_BE[3:0]/
(Driven by Master)

Byte Enable

PAR
(Driven by Master-Addr;
LSI53C875A-Data)

IRDY/
(Driven by Master)
TRDY/
(Driven by LSI53C875A)
STOP/
(Driven by LSI53C875A)
DEVSEL/
(Driven by LSI53C875A)
MAD
(Driven by LSI53C875A;

Data Out

Lower
Address

Data Out

MAS1/
(Driven by LSI53C875A)
MAS0/
(Driven by LSI53C875A)
MCE/
(Driven by LSI53C875A)

MOE/
(Driven by LSI53C875A)

MWE/
(Driven by LSI53C875A)

PCI and External Memory Interface Timing Diagrams

6-47

Table 6.33
Symbol

Slow Memory (≤= 128 Kbytes) Read Cycle
Parameter

Min

Max

Unit

t11

Address setup to MAS/ HIGH

–

t12

Address hold from MAS/ HIGH

–

t13

MAS/ pulse width

–

t14

MCE/ LOW to data clocked in

150

–

t15

Address valid to data clocked in

205

–

t16

MOE/ LOW to data clocked in

100

–

t17

Data hold from address, MOE/, MCE/ change

–

t18

Address out from MOE/, MCE/ HIGH

–

t19

Data setup to CLK HIGH

–

Figure 6.29 Slow Memory (≤= 128 Kbytes) Read Cycle
CLK
Valid Read Data

t17

MAD

Higher
Address

(Address driven by LSI53C875A;
Data driven by Memory)

Middle
Lower
Address Address

t12

t11
MAS1/
(Driven by LSI53C875A)
t13

t19

t15

MAS0/
(Driven by LSI53C875A)
t14
MCE/
(Driven by LSI53C875A)
t16
MOE/
(Driven by LSI53C875A)
MWE/
(Driven by LSI53C875A)

6-48

Electrical Specifications

t18

Table 6.34
Symbol

Slow Memory (≤ 128 Kbytes) Write Cycle
Parameter

Min

Max

Unit

t11

Address setup to MAS/ HIGH

–

t12

Address hold from MAS/ HIGH

–

t13

MAS/ pulse width

–

t20

Data setup to MWE/ LOW

–

t21

Data hold from MWE/ HIGH

–

t22

MWE/ pulse width

100

–

t23

Address setup to MWE/ LOW

–

t24

MCE/ LOW to MWE/ HIGH

120

–

t25

MCE/ LOW to MWE/ LOW

–

t26

MWE/ HIGH to MCE/ HIGH

–

Figure 6.30 Slow Memory (≤= 128 Kbytes) Write Cycle
CLK

MAD
(Driven by LSI53C875A)

Higher
Address

Middle
Address

Lower
Address

Valid Write Data

t12

t11
MAS1/
(Driven by LSI53C875A)
t13
MAS0/
(Driven by LSI53C875A)

t24
MCE/
(Driven by LSI53C875A)
t25

t26

MOE/
(Driven by LSI53C875A)
t22

t20

t21

MWE/
(Driven by LSI53C875A)
t23

PCI and External Memory Interface Timing Diagrams

6-49

Table 6.35
Symbol

≤= 64 Kbytes ROM Read Cycle
Parameter

Min

Max

Unit

t11

Address setup to MAS/ HIGH

–

t12

Address hold from MAS/ HIGH

–

t13

MAS/ pulse width

–

t14

MCE/ LOW to data clocked in

150

–

t15

Address valid to data clocked in

205

–

t16

MOE/ LOW to data clocked in

100

–

t17

Data hold from address, MOE/, MCE/ change

–

t18

Address out from MOE/, MCE/ HIGH

–

t19

Data setup to CLK HIGH

–

Figure 6.31 ≤ 64 Kbytes ROM Read Cycle
CLK
t17
MAD
(Address driven by LSI53C875A;

Data driven by Memory)
MAS1/
(Driven by LSI53C875A)

Higher
Address

Valid
Read
Data

Lower
Address

t12

t19

t11

t13
MAS0/
(Driven by LSI53C875A)

t15

t14

MCE/
(Driven by LSI53C875A)
t16
MOE/
(Driven by LSI53C875A)
MWE/
(Driven by LSI53C875A)

6-50

Electrical Specifications

t18

Table 6.36
Symbol

≤= 64 Kbyte ROM Write Cycle
Parameter

Min

Max

Unit

t11

Address setup to MAS/ HIGH

–

t12

Address hold from MAS/ HIGH

–

t13

MAS/ pulse width

–

t20

Data setup to MWE/ LOW

–

t21

Data hold from MWE/ HIGH

–

t22

MWE/ pulse width

100

–

t23

Address setup to MWE/ LOW

–

t24

MCE/ LOW to MWE/ HIGH

120

–

t25

MCE/ LOW to MWE/ LOW

–

t26

MWE/ HIGH to MCE/ HIGH

–

Figure 6.32 ≤ 64 Kbyte ROM Write Cycle
CLK

MAD
(Driven by LSI53C875A)

Higher
Address

t11

Lower
Address

Valid Write Data

t12

MAS1/
(Driven by LSI53C875A)
t13
MAS0/
(Driven by LSI53C875A)

t24

MCE/
(Driven by LSI53C875A)
t26

t25
MOE/
(Driven by LSI53C875A)

t21

t20

MWE/
(Driven by LSI53C875A)
t23

t22

PCI and External Memory Interface Timing Diagrams

6-51

6.5 SCSI Timing Diagrams
The tables and diagrams in this section describe the LSI53C875A SCSI
timings.

Table 6.37
Symbol

Initiator Asynchronous Send
Parameter

Min

Max

Unit

SACK/ asserted from SREQ/ asserted

–

SACK/ deasserted from SREQ/ deasserted

–

Data setup to SACK/ asserted

–

Data hold from SREQ/ deasserted

–

Figure 6.33 Initiator Asynchronous Send
SREQ/

n+1
t1

SACK/

t3
SD[15:0]/
SDP[1:0]/

6-52

n+1

n
t4
Valid n

Electrical Specifications

Valid n + 1

Table 6.38
Symbol

Initiator Asynchronous Receive
Parameter

Min

Max

Unit

SACK/ asserted from SREQ/ asserted

–

SACK/ deasserted from SREQ/ deasserted

–

Data setup to SREQ/ asserted

–

Data hold from SACK/ asserted

–

Figure 6.34 Initiator Asynchronous Receive
SREQ/

n+1
t1

SACK/

n+1

n
t4

t3
SD[15:0]/,
SDP[1:0]/

Valid n

SCSI Timing Diagrams

Valid n + 1

6-53

Table 6.39
Symbol

Target Asynchronous Send
Parameter

Min

Max

Unit

SREQ/ deasserted from SACK/ asserted

–

SREQ/ asserted from SACK/ deasserted

–

Data setup to SREQ/ asserted

–

Data hold from SACK/ asserted

–

Figure 6.35 Target Asynchronous Send

SREQ/

n+1

t1
SACK/

n
t3

SD[15:0]/,
SDP[1:0]/

6-54

t2
n+1

t4
Valid n

Electrical Specifications

Valid n + 1

Table 6.40
Symbol

Target Asynchronous Receive
Parameter

Min

Max

Unit

SREQ/ deasserted from SACK/ asserted

–

SREQ/ asserted from SACK/ deasserted

–

Data setup to SACK/ asserted

–

Data hold from SREQ/ deasserted

–

Figure 6.36 Target Asynchronous Receive
SREQ/

n+1

n
t2

t1
SACK/

n
t3

SD[15:0]/,
SDP[1:0]/

Table 6.41
Symbol

n+1
t4

Valid n

Valid n + 1

SCSI-1 Transfers (5.0 Mbytes)
Parameter

Min

Max

Unit

Send SREQ/ or SACK/ assertion pulse width

–

Send SREQ/ or SACK/ deassertion pulse width

–

Receive SREQ/ or SACK/ assertion pulse width

–

Receive SREQ/ or SACK/ deassertion pulse width

–

Send data setup to SREQ/ or SACK/ asserted

–

Send data hold from SREQ/ or SACK/ asserted

–

Receive data setup to SREQ/ or SACK/ asserted

–

Receive data hold from SREQ/ or SACK/ asserted

–

SCSI Timing Diagrams

6-55

Table 6.42

Symbol

SCSI-2 Fast Transfers 10.0 Mbytes (8-Bit Transfers) or 20.0 Mbytes
(16-Bit Transfers) 40 MHz Clock
Parameter

Min

Max

Unit

Send SREQ/ or SACK/ assertion pulse width

–

Send SREQ/ or SACK/ deassertion pulse width

–

Receive SREQ/ or SACK/ assertion pulse width

–

Receive SREQ/ or SACK/ deassertion pulse width

–

Send data setup to SREQ/ or SACK/ asserted

–

Send data hold from SREQ/ or SACK/ asserted

–

Receive data setup to SREQ/ or SACK/ asserted

–

Receive data hold from SREQ/ or SACK/ asserted

–

Min

Max

Unit

Table 6.43

Symbol

Ultra SCSI Transfers 20.0 Mbytes (8-Bit Transfers) or
40.0 Mbytes (16-Bit Transfers) Quadrupled 40 MHz Clock1, 2
Parameter

Send SREQ/ or SACK/ assertion pulse width

–

Send SREQ/ or SACK/ deassertion pulse width

–

Receive SREQ/ or SACK/ assertion pulse width

–

Receive SREQ/ or SACK/ deassertion pulse width

–

Send data setup to SREQ/ or SACK/ asserted

–

Send data hold from SREQ/ or SACK/ asserted

–

Receive data setup to SREQ/ or SACK/ asserted

–

Receive data hold from SREQ/ or SACK/ asserted

–

1. Transfer period bits (bits [6:4] in the SCSI Transfer (SXFER) register) are set to zero and the Extra
Clock Cycle of Data Setup bit (bit 7 in SCSI Control One (SCNTL1)) is set.
2. During Ultra SCSI transfers, the value of the Extend REQ/ACK Filtering bit (SCSI Test Two
(STEST2), bit 1) has no effect.

6-56

Electrical Specifications

Figure 6.37 Initiator and Target Synchronous Transfer
t1
SREQ/
or SACK/

n
t3

Send Data
SD[15:0]/, SDP[1:0]/

n+1

t4
Valid n

t5
Receive Data
SD[15:0]/,
SDP[1:0]/

Valid n + 1

t6
Valid n

SCSI Timing Diagrams

Valid n + 1

6-57

6.6 Package Diagrams
This section of the manual has a package drawing and pinout for both
the PQFP and BGA.
Figure 6.38 LSI53C875A 160-Pin PQFP Mechanical Drawing

Important:

6-58

This drawing may not be the latest version. For board layout and manufacturing, obtain the
most recent engineering drawings from your LSI Logic marketing representative by
requesting the outline drawing for package code P3.

Electrical Specifications

Figure 6.38 160-pin PQFP (P3) Mechanical Drawing (Sheet 2 of 2)

Important:

Package Diagrams

6-59

Table 6.44
Signal
C_BE[3]/
IDSEL
PCI_AD[23]
VSSIO
PCI_AD[22]
PCI_AD[21]
PCI_AD[20]
VDDIO
PCI_AD[19]
VSSIO
PCI_AD[18]
PCI_AD[17]
PCI_AD[16]
VSSIO
C_BEN[2]
FRAME/
IRDY/
VSSIO
TRDY/
DEVSEL/
VDDIO
STOP/
VSSIO
PERR/
PAR
C_BEN[1]/
VSSIO
PCI_AD[15]
PCI_AD[14]
PCI_AD[13]
VSSIO
PCI_AD[12]
VDDIO
PCI_AD[11]
PCI_AD[10]
PCI_AD[9]
VSSIO
PCI_AD[8]
C_BEN[0]/
PCI_AD[7]

160 PQFP Pin List by Location
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

Signal
Pin
PCI_AD[6]
41
VSSIO
42
PCI_AD[5]
43
PCI_AD[4]
44
VDDIO
45
PCI_AD[3]
46
PCI_AD[2]
47
VSSIO
48
PCI_AD[1]
49
PCI_AD[0]
50
VDDCORE
51
IRQ/
52
GPIO[0]
53
GPIO[1]
54
VSSCORE
55
SCLK
56
TMS/
57
TDO/
58
MAD[7]
59
MAD[6]
60
MAD[5]
61
MAD[4]
62
VDDIO
63
MAD[3]
64
MAD[2]
65
MAD[1]
66
MAD[0]
67
GPIO[2]
68
VSSIO
69
GPIO[3]
70
GPIO[4]
71
NC1
72
NC
73
VDDIO
74
NC
75
NC
76
MACN_TESTOUT 77
NC
78
VSSIO
79
VSSCORE
80

1. NC pins are not connected.

6-60

Electrical Specifications

Signal
NC
NC
VDDCORE
VDDSCSI
SD[11]/
SD[10]/
SD[9]/
VSSIO
SD[8]/
IO/
REQ/
CD/
VSSSIO
SEL/
MSG/
RST/
ACK/
BSY/
VSSIO
ATN/
SDP[0]/
SD[7]/
SD[6]/
VSSIO
SD[5]/
SD[4]/
SD[3]/
SD[2]/
VSSIO
SD[1]/
SD[0]/
SDP[1]/
SD[15]/
VSSIO
SD[14]/
SD[13]/
SD[12]/
VDDIO
NC
NC

Pin
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120

Signal
NC
NC
VSSIO
NC
NC
TEST_HSC/
TEST_RST/
VDDIO
VDDA
TCK
TRST/
VSSA
VSSIO
NC
NC
MASN[1]/
MASN[0]/
VDDIO
MEW/
MOE/
MCE/
TDI
SERR/
RST/
CLK
VSSCORE
GNT/
REQ/
VDDCORE
PCI_AD[31]
PCI_AD[30]
VSSIO
PCI_AD[29]
PCI_AD[28]
VDDIO
PCI_AD[27]
PCI_AD[26]
VSSIO
PCI_AD[25]
PCI_AD[24]

Pin
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160

Figure 6.39 169-Pin BGA Mechanical Drawing

Important:

Package Diagrams

6-61

Table 6.45

169 BGA Pin List by Location

Signal

C_BE[3]/
PCI_AD[24]
PCI_AD[27]
PCI_AD[29]
VDDCORE
CLK
MCE/
MAS[0]/
VSSIO
TCK
TEST_HSC/
NC1
NC
IDSEL
NC
NC
PCI_AD[28]
PCI_AD[31]
RST/
MOE/
MAS[1]/
VSSA
VDDIO
VSSIO
NC
NC
PCI_AD[21]
PCI_AD[23]
NC
PCI_AD[26]
PCI_AD[30]
VSSCORE
MWE/
NC
TRST/
TEST_RST/
NC
VDDIO
SD[13]
NC
VDDPCI1

A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
A12
A13
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B11
B12
B13
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
D1
D2

PCI_AD[20]D3
PCI_AD[25]
VDDIO
GNT/
TDI
NC
VDDA
NC
SD[12]
VSSIO
SD[15]
PCI_AD[16]
PCI_AD[17]
PCI_AD[18]
PCI_AD[19]
PCI_AD[22]
REQ/
SERR/
VDDIO
NC
SD[14]
SD[0]
SD[1]
VSSIO
IRDY/
FRAME/
C_BE[2]/
NC
NC
NC
SDP[1]
SD[2]
SD[3]
SD[4]
VSSIO
SD[5]
VDDIO
DEVSEL/
TRDY/
STOP/
NC

D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
E1
E2
E3
E4
E5
E6
E7
E8
E9
E10
E11
E12
E13
F1
F2
F3
F4
F5
F6
F8
F9
F10
F11
F12
F13
G1
G2
G3
G4
G5

SD[6]G9
SD[7]
VSSIO
ATN/
SDP[0]
PAR
PERR/
C_BE[1]/
NC
PCI_AD[15]
PCI_AD[12]
NC
SBSY
SSEL
SMSG
SRST
SACK
PCI_AD[14]
PCI_AD[13]
NC
PCI_AD[10]
VDDIO
TDO
VDDIO
GPIO[2]
SD[11]
SD[8]
SREQ
SCD
VSSIO
VDDIO
PCI_AD[11]
NC
C_BE[0]/
PCI_AD[1]
GPIO[1]
MAD[4]
MAD[0]
NC
VSSIO
SD[9]

1. NC pins are not connected.

6-62

Electrical Specifications

Pin
G10
G11
G12
G13
H1
H2
H3
H4
H5
H6
H8
H9
H10
H11
H12
H13
J1
J2
J3
J4
J5
J6
J7
J8
J9
J10
J11
J12
J13
K1
K2
K3
K4
K5
K6
K7
K8
K9
K10
K11

Signal

VSSIO
K12
SIO
K13
PCI_AD[9]
L1
PCI_AD[8]
L2
PCI_AD[4]
L3
PCI_AD[2]
L4
VDDCORE
L5
VSSCORE
L6
MAD[7]
L7
MAD[1]
L8
GPIO[4]
L9
MAC_TESTOUT/ L10
VDDIO
L11
VDDCORE
L12
SD[10]
L13
PCI_AD[7]
M1
NC
M2
PCI_AD[5]
M3
NC
M4
IRQ/
M5
SCLK
M6
MAD[6]
M7
MAD[3]
M8
GPIO[3]
M9
VDDIO
M10
NC
M11
NC
M12
NC
M13
PCI_AD[6]
N1
NC
N2
PCI_AD[3]
N3
PCI_AD[0]
N4
GPIO[0]
N5
TMS
N6
MAD[5]
N7
MAD[2]
N8
VSSIO
N9
NC
N10
NC
N11
VSSCORE
N12
NC
N13

Appendix A
Register Summary

Table A.1

LSI53C875A PCI Register Map

Address

Read/Write Page

Base Address Register One (MEMORY)

0x14–0x17

Read/Write

4-9

Base Address Register Two (SCRIPTS RAM)

0x18–0x1B

Read/Write

4-10

Base Address Register Zero (I/O)

0x10–0x13

Read/Write

4-9

Bridge Support Extensions (PMCSR_BSE)

0x46

Read Only

4-17

Cache Line Size

0x0C

Read/Write

4-7

Capabilities Pointer

0x34

Read Only

4-13

Capability ID

0x40

Read Only

4-15

Class Code

0x09–0x0B

Read Only

4-7

Command

0x04–0x05

Read/Write

4-3

Data

0x47

Read Only

4-18

Device ID

0x02–0x03

Read Only

4-3

Expansion ROM Base Address

0x30–0x33

Read/Write

4-12

Header Type

0x0E

Read Only

4-8

Interrupt Line

0x3C

Read/Write

4-13

Interrupt Pin

0x3D

Read Only

4-14

Latency Timer

0x0D

Read/Write

4-8

Max_Lat

0x3F

Read Only

4-14

Min_Gnt

0x3E

Read Only

4-14

Next Item Pointer

0x41

Read Only

4-15

LSI53C875A PCI to Ultra SCSI Controller

A-1

Table A.1

LSI53C875A PCI Register Map (Cont.)

Address

Read/Write Page

Power Management Capabilities (PMC)

0x42–0x43

Read Only

4-15

Power Management Control/Status (PMCSR)

0x44–0x45

Read/Write

4-16

Reserved

0x28–0x2B

–

4-10

Reserved

0x35–0x3B

–

4-13

Revision ID (Rev ID)

0x08

Read Only

4-6

Status

0x06–0x07

Read/Write

4-5

Subsystem ID

0x2E–0x2F

Read Only

4-11

Subsystem Vendor ID

0x2C–0x2D

Read Only

4-10

Vendor ID

0x00–0x01

Read Only

4-2

Table A.2

LSI53C875A SCSI Register Map

Address

Read/Write

Page

Adder Sum Output (ADDER)

0x3C–0x3F

Read Only

4-73

Chip Control 0 (CCNTL0)

0x56

Read/Write

4-95

Chip Control 1 (CCNTL1)

0x57

Read/Write

4-97

Chip Test Five (CTEST5)

0x22

Read/Write

4-60

Chip Test Four (CTEST4)

0x21

Read/Write

4-59

Chip Test One (CTEST1)

0x19

Read Only

4-53

Chip Test Six (CTEST6)

0x23

Read/Write

4-62

Chip Test Three (CTEST3)

0x1B

Read/Write

4-56

Chip Test Two (CTEST2)

0x1A

Read Only (bit 3 write) 4-54

Chip Test Zero (CTEST0)

0x18

Read/Write

4-53

Cumulative SCSI Byte Count (CSBC)

0xDC–0xDF

Read/Write

4-108

Data Structure Address (DSA)

0x10–0x13

Read/Write

4-47

DMA Byte Counter (DBC)

0x24–0x26

Read/Write

4-62

A-2

Table A.2

LSI53C875A SCSI Register Map (Cont.)

Address

Read/Write

Page

DMA Command (DCMD)

0x27

Read/Write

4-63

DMA Control (DCNTL)

0x3B

Read/Write

4-70

DMA FIFO (DFIFO)

0x20

Read/Write

4-57

DMA Interrupt Enable (DIEN)

0x39

Read/Write

4-69

DMA Mode (DMODE)

0x38

Read/Write

4-66

DMA Next Address (DNAD)

0x28–0x2B

Read/Write

4-64

DMA Next Address 64 (DNAD64)

0xB8–0xBB

Read/Write

4-103

DMA SCRIPTS Pointer (DSP)

0x2C–0x2F

Read/Write

4-64

DMA SCRIPTS Pointer Save (DSPS)

0x30–0x33

Read/Write

4-65

DMA Status (DSTAT)

0x0C

Read Only

4-39

DSA Relative Selector (DRS)

0xAC–0xAF

Read/Write

4-101

Dynamic Block Move Selector (DBMS)

0xB4–0xB7

Read/Write

4-103

Entry Storage Address (ESA)

0xD0–0xD3

Read/Write

4-106

General Purpose (GPREG0)

0x07

Read/Write

4-35

General Purpose Pin Control Zero (GPCNTL0)

0x47

Read/Write

4-82

Instruction Address (IA)

0xD4–0xD7

Read/Write

4-107

Interrupt Status One (ISTAT1)

0x15

Read/Write

4-51

Interrupt Status Zero (ISTAT0)

0x14

Read/Write

4-48

Mailbox One (MBOX1)

0x17

Read/Write

4-52

Mailbox Zero (MBOX0)

0x16

Read/Write

4-52

Memory Access Control (MACNTL)

0x46

Read/Write

4-81

Memory Move Read Selector (MMRS)

0xA0–0xA3

Read/Write

4-100

Memory Move Write Selector (MMWS)

0xA4–0xA7

Read/Write

4-100

Phase Mismatch Jump Address 1 (PMJAD1)

0xC0–0xC3

Read/Write

4-104

Phase Mismatch Jump Address 2 (PMJAD2)

0xC4–0xC7

Read/Write

4-104

A-3

Table A.2

LSI53C875A SCSI Register Map (Cont.)

Address

Read/Write

Page

Remaining Byte Count (RBC)

0xC8–0xCB

Read/Write

4-105

Reserved

0x53

–

4-94

Reserved

0x5A–0x5B

–

4-99

Reserved

0xBC–0xBF

–

4-103

Reserved

0xDB

–

4-108

Reserved

0xE0–0xFF

–

4-108

Response ID One (RESPID1)

0x4B

Read/Write

4-86

Response ID Zero (RESPID0)

0x4A

Read/Write

4-86

Scratch Byte Register (SBR)

0x3A

Read/Write

4-70

Scratch Register A (SCRATCHA)

0x34–0x37

Read/Write

4-65

Scratch Register B (SCRATCHB)

0x5C–0x5F

Read/Write

4-99

Scratch Registers C–R (SCRATCHC–SCRATCHR) 0x60–0x9F

Read/Write

4-99

SCRIPTS Fetch Selector (SFS)

0xA8–0xAB

Read/Write

4-101

SCSI Bus Control Lines (SBCL)

0x0B

Read Only

4-38

SCSI Bus Data Lines (SBDL)

0x58–0x59

Read Only

4-98

SCSI Byte Count (SBC)

0xD8–0xDA

Read Only

4-107

SCSI Chip ID (SCID)

0x04

Read/Write

4-30

SCSI Control One (SCNTL1)

0x01

Read/Write

4-23

SCSI Control Three (SCNTL3)

0x03

Read/Write

4-28

SCSI Control Two (SCNTL2)

0x02

Read/Write

4-26

SCSI Control Zero (SCNTL0)

0x00

Read/Write

4-20

SCSI Destination ID (SDID)

0x06

Read/Write

4-35

SCSI First Byte Received (SFBR)

0x08

Read/Write

4-36

SCSI Input Data Latch (SIDL)

0x50–0x51

Read Only

4-93

SCSI Interrupt Enable One (SIEN1)

0x41

Read/Write

4-75

A-4

Table A.2

LSI53C875A SCSI Register Map (Cont.)

Address

Read/Write

Page

SCSI Interrupt Enable Zero (SIEN0)

0x40

Read/Write

4-73

SCSI Interrupt Status One (SIST1)

0x43

Read Only

4-78

SCSI Interrupt Status Zero (SIST0)

0x42

Read Only

4-76

SCSI Longitudinal Parity (SLPAR)

0x44

Read/Write

4-79

SCSI Output Control Latch (SOCL)

0x09

Read/Write

4-37

SCSI Output Data Latch (SODL)

0x54–0x55

Read/Write

4-94

SCSI Selector ID (SSID)

0x0A

Read Only

4-38

SCSI Status One (SSTAT1)

0x0E

Read Only

4-43

SCSI Status Two (SSTAT2)

0x0F

Read Only

4-46

SCSI Status Zero (SSTAT0)

0x0D

Read Only

4-42

SCSI Test Four (STEST4)

0x52

Read Only

4-94

SCSI Test One (STEST1)

0x4D

Read/Write

4-88

SCSI Test Three (STEST3)

0x4F

Read/Write

4-91

SCSI Test Two (STEST2)

0x4E

Read/Write

4-89

SCSI Test Zero (STEST0)

0x4C

Read Only

4-87

SCSI Timer One (STIME1)

0x49

Read/Write

4-85

SCSI Timer Zero (STIME0)

0x48

Read/Write

4-83

SCSI Transfer (SXFER)

0x05

Read/Write

4-31

SCSI Wide Residue (SWIDE)

0x45

Read/Write

4-81

Static Block Move Selector (SBMS)

0xB0–0xB3

Read/Write

4-102

Temporary (TEMP)

0x1C–0x1F

Read/Write

4-57

Updated Address (UA)

0xCC–0xCF

Read/Write

4-105

A-5

A-6

Appendix B
External Memory
Interface Diagram
Examples
Appendix B has example external memory interface diagrams.
Figure B.1

16 Kbyte Interface with 200 ns Memory
MOE/
OE
MCE/

MAD[7:0]
Bus

A[7:0]

VDD
MAD0

D[7:0]

A[13:8]

4.7 K

27C128

LSI53C875A
MAS0/

6
MAS1/

D0
Q0
HCT374
D7
Q7
CK
QE

D0
Q0
HCT374
D5
Q5
CK
QE

Note: MAD[3:1] pulled LOW internally. MAD bus sense logic enabled for 16 Kbyte of slow memory (200 ns
devices @ 33 MHz).

LSI53C875A PCI to Ultra SCSI Controller

B-1

Figure B.2

64 Kbyte Interface with 150 ns Memory
Optional - for Flash Memory only, not
required for EEPROMS.

VPP
+ 12 V
VPP
Control

GPIO4
MWE/

MOE/
OE
MCE/

MAD[7:0]
Bus

A[7:0]

VDD
MAD2

D[7:0]

A[15:8]

4.7 K

27C512-15/
28F512-15/
Socket

LSI53C875A
8
MAS0/

6
MAS1/

D0
Q0
HCT374
D7
Q7
QE
CK

D0
Q0
HCT374
D7
Q7
CK
QE

Note: MAD 3, 1, 0 pulled LOW internally. MAD bus sense logic enabled for 64 Kbyte of fast memory (150 ns
devices @ 33 MHz).

B-2

External Memory Interface Diagram Examples

Figure B.3

128 Kbytes, 256 Kbytes, 512 Kbytes, or 1 Mbyte Interface with 150 ns
Memory
Optional - for Flash Memory only, not
required for EEPROMS.

VPP
+ 12 V
VPP
Control

GPIO4
MWE/

MOE/
OE
MCE/

MAD[7:0]
Bus

A[7:0]

VDD
MAD3

D[7:0]

A[15:8]

4.7 K

27C020-15/
28F020-15/
Socket

A[19:16]
LSI53C875A
8
MAS0/

6
MAS1/

D0
Q0
HCT374
D7
Q7
CK
QE

MAD[3:0]
D0
Q0
Bus
HCT377
4
Q3
D3
CK
E
Note: MAD[2:0] pulled LOW internally. MAD bus sense logic enabled for 128, 256, 512 Kbytes, or 1 Mbyte of fast
memory (150 ns devices @ 33 MHz). The HCT374s may be replaced with HCT377s.

External Memory Interface Diagram Examples

B-3

Figure B.4

512 Kbyte Interface with 150 ns Memory
Optional - for Flash Memory only, not
required for EEPROMS.
27C010-15/28F010-15 Sockets
VPP
+ 12 V
VPP
Control

GPIO4
MWE/

D[7:0]

A16

MOE/

MAD[7:0]
Bus

VDD
MAD3

4.7 K

MAD1

4.7 K

MAD3

4.7 K

LSI53C875A
8
MAS0/

MAS1/

MCE/

A[7:0]

D[7:0]

A[15:8]

.
.
.

D0
Q0
HCT374
D7
Q7
CK
QE

D0
Q0
8 HCT374
D7
Q7
CK
QE
MAD[2:0]
Bus
Q0
D0
3 D2
HCT377
CK
Q2
E

A
B

Y0
Y1
Y2

HCT139
Note: MAD2 pulled LOW internally. MAD bus sense logic enabled for 512 Kbytes of slow memory (150 ns
devices, additional time required for HCT139 @ 33 MHz). The HCT374s may be replaced with HCT377s.

B-4

External Memory Interface Diagram Examples

Index

Symbols
(64TIMOD) 4-97
(A7) 5-23
(AAP) 4-22
(ABRT) 4-40, 4-48
(ACK) 4-37, 4-39
(ADB) 4-23
(ADCK) 4-60
(ADDER) 4-73
(AESP) 4-24
(AIP) 4-43
(APS) 4-16
(ARB[1:0]) 4-20
(ART) 4-87
(ATN) 4-37, 4-39
(AWS) 4-90
(BAR0) 4-9
(BAR1) 4-9
(BAR2) 4-10
(BBCK) 4-61
(BDIS) 4-59
(BF) 4-40, 4-69
(BL[1:0]) 4-66
(BL2) 4-61
(BO) 4-57
(BO[9:8]) 4-62
(BOF) 4-68
(BSE) 4-17
(BSY) 4-37, 4-39
(C_D) 4-37, 4-39, 4-45
(CC) 4-7
(CCF[2:0]) 4-29
(CCNTL0) 4-95
(CCNTL1) 4-97
(CHM) 4-26
(CID) 4-15
(CIO) 4-54
(CLF) 4-56
(CLS) 4-7
(CLSE) 4-70
(CM) 4-54
(CMP) 4-74, 4-77
(COM) 4-72
(CON) 4-24, 4-49
(CP) 4-13
(CSBC) 4-108
(CSF) 4-92
(CTEST0) 4-53
(CTEST1) 4-53
(CTEST2) 4-54

(CTEST3) 4-56
(CTEST4) 4-59
(CTEST5) 4-60
(CTEST6) 4-62
(D1S) 4-16
(D2S) 4-16
(DACK) 4-55
(DATA) 4-18
(DBC) 4-62
(DBMS) 4-103
(DCMD) 4-63
(DCNTL) 4-70
(DDAC) 4-97
(DDIR) 4-54, 4-61
(DF) 4-62
(DFE) 4-39
(DFIFO) 4-57
(DFS) 4-61
(DHP) 4-23
(DID) 4-3
(DIEN) 4-69
(DILS) 4-96
(DIOM) 4-67
(DIP) 4-50
(DMODE) 4-66
(DNAD) 4-64
(DNAD64) 4-103
(DPE) 4-5
(DPR) 4-6
(DRD) 4-82
(DREQ) 4-55
(DRS) 4-102
(DSA) 4-47
(DSCL) 4-17
(DSI) 4-16, 4-92
(DSLT) 4-17
(DSP) 4-64
(DSPS) 4-65
(DSTAT) 4-39
(DT[1:0]) 4-5
(DWR) 4-82
(EBM) 4-4
(EIS) 4-4
(EMS) 4-4
(EN64DBMV) 4-98
(EN64TIBMV) 4-98
(ENC) 4-30, 4-35
(ENID) 4-38
(ENNDJ) 4-96
(ENPMJ) 4-95
(EPC) 4-22
(EPER) 4-3

LSI53C875A PCI to Ultra SCSI Controller

IX-1

(ERBA) 4-12
(ERL) 4-67
(ERMP) 4-68
(ESA) 4-106
(EWS) 4-29
(EXC) 4-23
(EXT) 4-90
(FBL3) 4-59
(FE) 4-82
(FF[3:0]) 4-43
(FF4) 4-46
(FFL) 4-53
(FLF) 4-56
(FLSH) 4-51
(FM) 4-56
(FMT) 4-53
(GEN) 4-75, 4-79
(GEN[3:0]) 4-85
(GENSF) 4-85
(GPCNTL0) 4-82
(GPIO) 4-35
(GPIO[1:0]) 4-83
(GPIO[4:2]) 4-83
(GPREG0) 4-35
(HSC) 4-91
(HT) 4-8
(HTH) 4-76, 4-79
(HTH[3:0]) 4-83
(HTHBA) 4-85
(HTHSF) 4-85
(I/O) 4-9, 4-37, 4-45
(I_O) 4-39
(IA) 4-107
(IARB) 4-24
(IID) 4-40, 4-69
(IL) 4-13
(ILF) 4-42
(ILF1) 4-46
(INTF) 4-49
(IP) 4-14
(IRQD) 4-72
(IRQM) 4-71
(ISO) 4-88
(ISTAT0) 4-48
(ISTAT1) 4-51
(LDSC) 4-47
(LEDC) 4-83
(LOA) 4-43
(LOCK) 4-94
(LOW) 4-90
(LT) 4-8
(M/A) 4-73
(MACNTL) 4-81
(MAN) 4-68
(MASR) 4-61
(MBOX0) 4-52
(MBOX1) 4-52
(MDPE) 4-40, 4-69
(ME) 4-82
(MEMORY) 4-9
(MG) 4-14
(ML) 4-14
(MMRS) 4-100
(MMWS) 4-101
(MO[4:0]) 4-33
(MPEE) 4-59

IX-2

(MSG) 4-37, 4-39, 4-45
(NC) 4-6
(NIP) 4-15
(OLF) 4-42
(OLF1) 4-46
(ORF) 4-42
(ORF1) 4-46
(PAR) 4-75, 4-78
(PCICIE) 4-54
(PEN) 4-17
(PFEN) 4-70
(PFF) 4-70
(PMC) 4-15
(PMCSR) 4-16
(PMCSR_BSE) 4-17
(PMEC) 4-16
(PMES) 4-15
(PMJAD1) 4-104
(PMJAD2) 4-104
(PMJCTL) 4-95
(PSCPT) 4-82
(PST) 4-16
(PWS[1:0]) 4-17
(QEN) 4-88
(QSEL) 4-89
(RBC) 4-105
(REQ) 4-37, 4-39
(RESPID0) 4-86
(RESPID1) 4-86
(RID) 4-6
(RMA) 4-5
(ROF) 4-89
(RRE) 4-30
(RSL) 4-74, 4-77
(RST) 4-24, 4-43, 4-75, 4-78
(RTA) 4-5
(S16) 4-92
(SBC) 4-107
(SBCL) 4-38
(SBDL) 4-98
(SBMS) 4-102
(SBR) 4-70
(SCE) 4-89
(SCF[2:0]) 4-29
(SCID) 4-30
(SCLK) 4-88
(SCNTL0) 4-20
(SCNTL1) 4-23
(SCNTL2) 4-26
(SCNTL3) 4-28
(SCPTS) 4-82
(SCRATCHA) 4-65
(SCRATCHB) 4-99
(SCRATCHC–SCRATCHR) 4-99
(SCRIPTS RAM) 4-10
(SDID) 4-35
(SDP0) 4-43
(SDP0L) 4-45
(SDP1) 4-47
(SDU) 4-26
(SE) 4-3
(SEL) 4-37, 4-39, 4-74, 4-77
(SEL[3:0]) 4-84
(SEM) 4-49
(SFBR) 4-36
(SFS) 4-101

Index

(SGE) 4-74, 4-77
(SI) 4-51
(SID) 4-11
(SIEN0) 4-73
(SIEN1) 4-75
(SIGP) 4-49, 4-54
(SIOM) 4-67
(SIP) 4-50
(SIR) 4-40
(SIST0) 4-76
(SIST1) 4-78
(SLB) 4-89
(SLPAR) 4-79
(SLPHBEN) 4-27
(SLPMD) 4-27
(SLT) 4-87
(SOCL) 4-37
(SODL) 4-94
(SOM) 4-88
(SOZ) 4-87
(SPL1) 4-47
(SRE) 4-30
(SRST) 4-48
(SRTM) 4-59
(SRUN) 4-51
(SSAID) 4-87
(SSE) 4-5
(SSI) 4-40, 4-69
(SSID) 4-38
(SSM) 4-71
(SST) 4-25
(SSTAT0) 4-42
(SSTAT1) 4-43
(SSTAT2) 4-46
(START) 4-21
(STD) 4-72
(STEST0) 4-87
(STEST1) 4-88
(STEST2) 4-89
(STEST3) 4-91
(STEST4) 4-94
(STIME0) 4-83
(STIME1) 4-85
(STO) 4-75, 4-79
(STR) 4-91
(STW) 4-93
(SWIDE) 4-81
(SXFER) 4-31
(SZM) 4-90
(TE) 4-91
(TEMP) 4-57
(TEOP) 4-55
(TP[2:0]) 4-31
(TRG) 4-22
(TTM) 4-92
(TYP) 4-81
(UA) 4-105
(UDC) 4-74, 4-78
(USE) 4-28
(V) 4-56
(VAL) 4-38
(VER[2:0]) 4-16
(VID) 4-2
(VUE0) 4-27
(VUE1) 4-27
(WATN) 4-22

(WIE) 4-4
(WOA) 4-43
(WRIE) 4-57
(WSR) 4-28
(WSS) 4-27
(ZMODE) 4-97
(ZSD) 4-59

Numerics
16-bit system (S16) 4-92
32-bit addressing 5-7
3-state 3-3
64-bit
addressing in SCRIPTS 2-19
SCRIPT selectors 4-99
table indirect indexing mode (64TIMOD) 4-97

A
A[6:0] 5-23
abort operation (ABRT) 4-48
aborted (ABRT) 4-40, 4-69
absolute maximum stress ratings 6-2
AC characteristics 6-9
adder sum output (ADDER) 4-73
address/data bus 2-3
always wide SCSI (AWS) 4-90
arbitration
in progress (AIP) 4-43
mode bits 1 and 0 (ARB[1:0]) 4-20
priority encoder test (ART) 4-87
assert
even SCSI parity (force bad parity) (AESP) 4-24
SATN/ on parity error (AAP) 4-22
SCSI
ACK/ signal (ACK) 4-37
ATN/ signal (ATN) 4-37
BSY/ signal (BSY) 4-37
C_D/ signal (C_D) 4-37
data bus (ADB) 4-23
I_O/ signal (I/O) 4-37
MSG/ signal (MSG) 4-37
REQ/ signal (REQ) 4-37
RST/ signal (RST) 4-24
SEL/ signal (SEL) 4-37
asynchronous SCSI
receive 2-31
send 2-29
auxiliary power source (APS) 4-16

B
base address register
one (BAR1) 2-3, 4-9
two (BAR2) 4-10
zero - I/O (BAR0) 4-9
bidirectional 3-3
signals 6-3
BIOS 2-3
bits used for parity control and generation 2-25
block move 2-9
instruction 5-6
bridge support extensions (BSE) 4-17
burst
disable (BDIS) 4-59

Index

IX-3

burst (Cont.)
length (BL[1:0]) 4-66
length bit 2 (BL2) 4-61
opcode fetch enable (BOF) 4-68
size selection 2-6
bus
command and byte enables 3-5
fault (BF) 4-40, 4-69
byte
count 5-37
empty in DMA FIFO (FMT) 4-53
full in DMA FIFO (FFL) 4-53
offset counter (BO) 4-57

C
cache line size 2-7, 2-9
(CLS) 4-7
enable (CLSE) 4-70
register 2-6
cache mode, see PCI cache mode 2-9
call instruction 5-27
Cap_ID (CID) 4-15
capabilities pointer (CP) 4-13
carry test 5-30
chained block moves 2-44
SCRIPTS instruction 2-47
SODL register 2-46
SWIDE register 2-46
wide SCSI receive bit 2-46
wide SCSI send bit 2-45
chained mode (CHM) 4-26
change bus phases 2-17
chip
control 0 (CCNTL0) 4-95
control 1 (CCNTL1) 4-97
revision level (V) 4-56
test five (CTEST5) 4-60
test one (CTEST1) 4-53
test six (CTEST6) 4-62
test three (CTEST3) 4-56
test two (CTEST2) 4-54
test zero (CTEST0) 4-53
type (TYP) 4-81
CHMOV 2-44
class code (CC) 4-7
clear DMA FIFO 2-42, 4-56
clear instruction 5-15, 5-17
clear SCSI FIFO (CSF) 4-92
CLF 2-42
CLK 3-4
clock 3-4
address incrementor (ADCK) 4-60
byte counter (BBCK) 4-61
conversion factor (CCF[2:0]) 4-29
quadrupler 2-20
CLSE 2-6, 2-7
CMP 2-39
compare
data 5-31
phase 5-31
configuration
read command 2-5
space 2-3
write command 2-5
configured

IX-4

Index

as I/O (CIO) 4-54
as memory (CM) 4-54
connected (CON) 4-24, 4-49
CSF 2-42
CTEST4 2-25
cumulative SCSI byte count (CSBC) 4-108
cycle frame 3-6

D
D1_Support (D1S) 4-16
D2_Support (D2S) 4-16
DACs 2-19
data
(DATA) 4-18
acknowledge status (DACK) 4-55
compare mask 5-31
compare value 5-32
parity error reported (DPR) 4-6
paths 2-28
request status (DREQ) 4-55
structure address (DSA) 4-47
transfer direction (DDIR) 4-54
data read (DRD) 4-82
data write (DWR) 4-82
data_scale (DSCL) 4-17
data_select (DSLT) 4-17
data-in 2-47
data-out 2-47
DCNTL 2-6, 2-39
decode of MAD pins 3-14
default download mode 2-50
destination
address 5-23
I/O memory enable (DIOM) 4-67
detected parity error (from slave) (DPE) 4-5
determining the data transfer rate 2-34
device
ID (DID) 4-3
select 3-6
specific initialization (DSI) 4-16
DEVSEL/ 3-6
timing (DT[1:0]) 4-5
DIEN 2-25, 2-39, 2-40
DIP 2-38, 2-41, 2-42, 2-43
direct 5-19
disable
auto FIFO clear (DISFC) 4-96
dual address cycle (DDAC) 4-97
halt on parity error or ATN (target only) (DHP) 4-23
internal load and store (DILS) 4-96
single initiator response (DSI) 4-92
disconnect 2-17
disconnect instruction 5-15
DMA
byte counter (DBC) 4-62
command (DCMD) 4-63
control (DCNTL) 4-70
direction (DDIR) 4-61
FIFO 2-8, 2-27, 2-38
(DF) 4-62
(DFIFO) 4-57
byte offset counter, bits [9:8] (BO[9:8]) 4-62
empty (DFE) 4-39
size (DFS) 4-61
interrupt 2-39, 2-40, 2-42
enable (DIEN) 4-69

DMA
interrupt (Cont.)
pending (DIP) 4-50
mode (DMODE) 4-66
SCRIPTS
pointer (DSP) 4-64
pointer save (DSPS) 4-65
status (DSTAT) 4-39
DMA next
address (DNAD) 4-64
address 64 (DNAD64) 4-103
DMODE 2-6
register 2-22
DSA
relative 5-36
relative selector (DRS) 4-102
DSPS register 5-34
DSTAT 2-38, 2-42, 2-43
dual address cycles
command 2-6
dynamic block move selector (DBMS) 4-103

general purpose
(GPREG0) 4-35
I/O (GPIO) 4-35
I/O pin 0 3-10
I/O pin 1 3-10
I/O pin 2 3-10
I/O pin 3 3-10
I/O pin 4 3-10
pin control zero (GPCNTL0) 4-82
timer expired (GEN) 4-75, 4-79
timer period (GEN[3:0]) 4-85
timer scale factor (GENSF) 4-85
GNT/ 3-7
GPIO enable, bits [1:0] (GPIO[1:0]) 4-83
GPIO enable, bits [4:2] (GPIO[4:2]) 4-83
GPIO0_ FETCH/ 3-10
GPIO1_ MASTER/ 3-10
GPIO2 3-10
GPIO3 3-10
GPIO4 3-10
grant 3-7

enable
64-bit
direct BMOV (EN64DBMV) 4-98
table indirect BMOV (EN64TIBMV) 4-98
bus mastering (EBM) 4-4
I/O space (EIS) 4-4
jump on nondata phase mismatches (ENNDJ) 4-96
memory space (EMS) 4-4
parity
checking 2-24
checking (EPC) 4-22
error response (EPER) 4-3
phase mismatch jump (ENPMJ) 4-95
read
line (ERL) 4-67
multiple (ERMP) 4-68
response to
reselection (RRE) 4-30
selection (SRE) 4-30
wide SCSI (EWS) 4-29
enabling cache mode 2-10
encoded
chip SCSI ID (ENC) 4-30
destination SCSI ID
(ENC) 4-35
(ENID) 4-38
SCSI destination ID 5-20
entry storage address (ESA) 4-106
error reporting signals 3-7
even parity 2-24
expansion ROM base
address (ERBA) 4-12
address register 2-49
extend SREQ/SACK filtering (EXT) 4-90
external
clock 6-9
memory interface 2-49
configuration 2-49
slow memory 2-49
external memory interface
multiple byte accesses 6-11
extra clock cycle of data setup (EXC) 4-23

Index

fetch
enable (FE) 4-82
pin mode (FM) 4-56
FIFO
byte control (FBL[2:0]) 4-60
byte control (FBL3) 4-59
flags (FF[3:0]) 4-43
flags, bit 4 (FF4) 4-46
first dword 5-6, 5-14, 5-22, 5-26, 5-36
flush DMA FIFO (FLF) 4-56
flushing (FLSH) 4-51
FRAME/ 3-6
frequency lock (LOCK) 4-94
full arbitration, selection/reselection 4-21
function complete 2-39
(CMP) 4-74, 4-77

H
halt SCSI clock (HSC) 4-91
halting 2-42
handshake-to-handshake timer
bus activity enable (HTHBA) 4-85
expired (HTH) 4-76, 4-79
period (HTH[3:0]) 4-83
scale factor (HTHSF) 4-85
hardware control of SCSI activity LED 2-19
hardware interrupts 2-37
header type (HT) 4-8
high impedance mode (SZM) 4-90
high impedance mode (ZMODE) 4-97

I
I/O 3-3
instructions 5-13
read command 2-5
space 2-2, 2-3
write command 2-5

IX-5

IDSEL 2-3, 3-6
signal 2-5
illegal instruction detected (IID) 4-40, 4-69
immediate
arbitration (IARB) 4-24
data 5-23
indirect addressing 5-6
initialization device select 3-6
initiator
mode 5-16
phase mismatch 4-76
ready 3-6
input 3-3
capacitance 6-2
instruction
address (IA) 4-107
block move 5-6
prefetch unit flushing 2-21
type 5-36
block move 5-6
I/O instruction 5-14
memory move 5-33
read/write instruction 5-22
transfer control instruction 5-26
internal
SCRIPTS RAM 2-18
internal RAM
see also SCRIPTS
RAM 2-18
interrupt
acknowledge command 2-4
handling 2-37
instruction 5-28
line (IL) 4-13
on-the-fly 5-30
on-the-fly (INTF) 4-49
on-the-fly instruction 5-28
output 6-10
pin (IP) 4-14
request 2-37, 3-8
signals 3-8
status one (ISTAT1) 4-51
status zero (ISTAT0) 4-48
interrupts 2-39
fatal vs. nonfatal interrupts 2-39
halting 2-42
IRQ disable bit 2-39
masking 2-40
sample interrupt service routine 2-43
stacked interrupts 2-41
IRDY/ 3-6
IRQ
disable (IRQD) 4-72
mode (IRQM) 4-71
IRQ/ 2-37, 3-8
pin 2-40, 2-43
issuing cache commands 2-10
ISTAT 2-37, 2-43

J
JTAG boundary scan testing 2-23
jump
address 5-32
call a relative address 5-29
call an absolute address 5-29

IX-6

Index

control (PMJCTL) 4-95
if true/false 5-30
instruction 5-26

L
last disconnect (LDSC) 4-47
latched SCSI parity
(SDP0L) 4-45
for SD[15:8] (SPL1) 4-47
latency 2-9
timer (LT) 4-8
LED_CNTL (LEDC) 4-83
load and store instructions 2-22, 5-37
prefetch unit and store instructions 2-22
loopback enable 2-23
lost arbitration (LOA) 4-43
LSI53C700 compatibility (COM) 4-72
LSI53C875A
new features 1-3

M
MAC/_TESTOUT 3-11
MAD
bus 2-49
bus programming 3-14
pins 2-49
MAD[0] 3-15
MAD[3:1] 3-14
MAD[6:4] 3-14
MAD[7:0] 3-12, 3-14
MAD[7] 3-14
mailbox one (MBOX1) 4-52
mailbox zero (MBOX0) 4-52
manual start mode (MAN) 4-68
MAS0/ 3-11
MAS1/ 3-11
masking 2-40
master
control for set or reset pulses (MASR) 4-61
data parity error (MDPE) 4-40, 4-69
enable (ME) 4-82
parity error enable (MPEE) 4-59
max SCSI synchronous offset (MO[4:0]) 4-33
Max_Lat (ML) 4-14
maximum stress ratings 6-2
MCE/ 3-11
memory
access control 3-11
(MACNTL) 4-81
address strobe 0 3-11
address strobe 1 3-11
address/data bus 3-12
chip enable 3-11
I/O address/DSA offset 5-37
move 2-9
move instructions 2-21, 5-32
no flush option 2-21
move read selector (MMRS) 4-100
move write selector (MMWS) 4-101
output enable 3-11
read 2-10, 2-11
read caching 2-11
read command 2-5
read line 2-10, 2-11

memory (Cont.)
read line command 2-6
read multiple 2-10, 2-11
read multiple command 2-6
space 2-2, 2-3
to memory 2-16
to memory moves 2-16
write 2-10, 2-11
write and invalidate 2-10
write and invalidate command 2-8
write caching 2-11
write command 2-5
write enable 3-11
Min_Gnt (MG) 4-14
MOE/ 3-11
move to/from SFBR cycles 5-24
multiple cache line transfers 2-8
MWE/ 3-11

N
new capabilities (NC) 4-6
new features in the LSI53C875A 1-3
Next_Item_Ptr (NIP) 4-15
no connections 3-13
no download mode 2-51
no flush 5-33
store instruction only 5-36
not supported 4-8, 4-10

target disconnect 2-9
target retry 2-9
PERR/ 3-7
phase mismatch
handling in SCRIPTS 2-17
jump address 1 (PMJAD1) 4-104
jump address 2 (PMJAD2) 4-104
jump registers 4-103
physical dword address and data 3-5
PME
clock (PMEC) 4-16
enable (PEN) 4-17
status (PST) 4-16
support (PMES) 4-15
pointer SCRIPTS (PSCPT) 4-82
polling 2-37
power
and ground signals 3-13
management 2-51
state (PWS[1:0]) 4-17
state D0 2-52
state D1 2-52
state D2 2-53
state D3 2-53
prefetch
enable (PFEN) 4-70
flush 2-22
flush (PFF) 4-70
SCRIPTS instructions 2-21
pull-ups, internal, conditions 3-3

opcode 5-9, 5-14, 5-22, 5-26
fetch burst capability 2-22
operating conditions 6-2
operator 5-22

RAM
see also SCRIPTS
RAM 2-18
read
line 2-10
function 2-7
modify-write cycles 5-23
multiple 2-7
multiple with read line enabled 2-7
write instructions 5-22
write system memory from SCRIPTS 5-34
read/write
instructions 5-22, 5-24
system memory from SCRIPTS 5-34
received
master abort (from master) (RMA) 4-5
target abort (from master) (RTA) 4-5
register
address 5-37
address - A[6:0] 5-23
registers 2-37
relative 5-19
relative addressing mode 5-18, 5-29
remaining byte count (RBC) 4-105
REQ/ 3-7
request 3-7
reselect 2-17
during reselection 2-33
instruction 5-14
reselected (RSL) 4-74, 4-77
reserved 4-3, 4-4, 4-5, 4-6, 4-10, 4-13, 4-16, 4-17, 4-22, 4-30,
4-35, 4-38, 4-40, 4-51, 4-69, 4-75, 4-79, 4-85, 4-88, 4-94,
4-96, 4-97, 4-99, 4-103, 4-108
command 2-5

P
PAR 3-5
parallel ROM interface 2-48
parallel ROM support 2-49
parity 2-26, 3-5
error 3-7
(PAR) 4-78
options 2-24
PCI
addressing 2-2
and external memory interface timing diagrams 6-11
bus commands and encoding types 2-4
bus commands and functions supported 2-3
cache line size register 2-8
cache mode 2-9
commands 2-3
configuration into enable (PCICIE) 4-54
configuration register read 6-13
configuration registers 4-1
configuration space 2-2
functional description 2-2
I/O space 2-3
interface signals 3-4
master transaction 2-10
master transfer 2-10
memory space 2-3
performance 1-6

Index

IX-7

reset 3-4
input 6-10
SCSI offset (ROF) 4-89
response ID one (RESPID1) 4-86
response ID zero (RESPID0) 4-86
return instruction 5-27
revision ID (RID) 4-6
ROM
flash and memory interface signals 3-11
pin 2-49
RST/ 3-4

S
SACK 2-42
SACK/ status (ACK) 4-39
SACs 2-19
SATN/ status (ATN) 4-39
SBSY/ status (BSY) 4-39
SC_D/ status (C_D) 4-39
SCLK 3-8
(SCLK) 4-88
quadrupler enable (QEN) 4-88
quadrupler select (QSEL) 4-89
SCNTL0 2-25
SCNTL1 2-24, 2-25
SCNTL3 2-36
scratch
byte register (SBR) 4-70
register A (SCRATCHA) 4-65
register B (SCRATCHB) 4-99
registers C–R (SCRATCHC–SCRATCHR) 4-99
script fetch selector (SFS) 4-101
SCRIPTS
(SCPTS) 4-82
instruction 2-46
interrupt instruction received (SIR) 4-40, 4-69
processor 2-17
internal RAM for instruction storage 2-18
performance 2-17
RAM 2-3, 2-18
running (SRUN) 4-51
SCSI
ATN condition - target mode (M/A) 4-73
bus control lines (SBCL) 4-38
bus data lines (SBDL) 4-98
bus interface 2-32
byte count (SBC) 4-107
C_D/ signal (C_D) 4-45
chip ID (SCID) 4-30
clock 3-8
control enable (SCE) 4-89
control one (SCNTL1) 4-23
control three (SCNTL3) 4-28
control two (SCNTL2) 4-26
control zero (SCNTL0) 4-20
data high impedance (ZSD) 4-59
destination ID (SDID) 4-35
disconnect unexpected (SDU) 4-26
encoded destination ID 5-20
FIFO test read (STR) 4-91
FIFO test write (STW) 4-93
first byte received (SFBR) 4-36
functional description 2-16
GPIO signals 3-10
gross error (SGE) 4-74, 4-77

IX-8

Index

I_O/ signal (I/O) 4-45
input data latch (SIDL) 4-93
instructions
block move 5-6
I/O 5-13
read/write 5-22
interface signals 3-8
interrupt enable one (SIEN1) 4-75
interrupt enable zero (SIEN0) 4-73
interrupt pending (SIP) 4-50
interrupt status one (SIST1) 4-78
interrupt status zero (SIST0) 4-76
interrupts 2-42
isolation mode (ISO) 4-88
longitudinal parity (SLPAR) 4-79
loopback mode 2-23
loopback mode (SLB) 4-89
low level mode (LOW) 4-90
MSG/ signal (MSG) 4-45
output control latch (SOCL) 4-37
output data latch (SODL) 4-94
parity control 2-26
parity error (PAR) 4-75
performance 1-5
phase 5-11, 5-28
phase mismatch - initiator mode 4-73
reset condition (RST) 4-75
RST/ received (RST) 4-78
RST/ signal (RST) 4-43
SCRIPTS operation 5-2
sample instruction 5-3
SDP0/ parity signal (SDP0) 4-43
SDP1 signal (SDP1) 4-47
selected as ID (SSAID) 4-87
selector ID (SSID) 4-38
serial EEPROM access 2-50
signals 3-9
status one (SSTAT1) 4-43
status two (SSTAT2) 4-46
status zero (SSTAT0) 4-42
synchronous offset maximum (SOM) 4-88
synchronous offset zero (SOZ) 4-87
synchronous transfer period (TP[2:0]) 4-31
termination 2-32
test four (STEST4) 4-94
test one (STEST1) 4-88
test three (STEST3) 4-91
test two (STEST2) 4-89
test zero (STEST0) 4-87
timer one (STIME1) 4-85
timer zero (STIME0) 4-83
TolerANT technology 1-4
transfer (SXFER) 4-31
true end of process (TEOP) 4-55
Ultra SCSI 2-20
valid (VAL) 4-38
wide residue (SWIDE) 4-81
SCSI-2
fast transfers
10.0 Mbytes (8-bit transfers)
40 MHz clock 6-56
20.0 Mbytes (16-bit transfers)
40 MHz clock 6-56
SCTRL signals 3-9
SD[15:0] 3-9
second dword 5-13, 5-21, 5-23, 5-32, 5-34, 5-37

SEL 2-39
select 2-17
instruction 5-16
with ATN/ 5-20
with SATN/ on a start sequence (WATN) 4-22
selected (SEL) 4-74, 4-77
selection or reselection time-out (STO) 4-75, 4-79
selection response logic test (SLT) 4-87
selection time-out (SEL[3:0]) 4-84
semaphore (SEM) 4-49
serial EEPROM
interface 2-50
SERR/ 3-7
SERR/ enable (SE) 4-3
set instruction 5-15, 5-17
set/clear
carry 5-20
SACK/ 5-21
shadow register test mode (SRTM) 4-59
SI_O/ status (I_O) 4-39
SID 2-51
SIDL
least significant byte full (ILF) 4-42
most significant byte full (ILF1) 4-46
SIEN0 2-39
SIEN1 2-39
signal process (SIGP) 4-49, 4-54
signaled system error (SSE) 4-5
simple arbitration 4-20
single
address cycles 2-19
ended SCSI signals 6-6
step interrupt (SSI) 4-40, 4-69
step mode (SSM) 4-71
SIP 2-38, 2-41, 2-42
SIST0 2-25, 2-38, 2-41, 2-43
SIST1 2-38, 2-41, 2-43
slow ROM pin 3-15
SLPAR high byte enable (SLPHBEN) 4-27
SLPAR mode (SLPMD) 4-27
SMSG/ status (MSG) 4-39
SODL
least significant byte full (OLF) 4-42
most significant byte full (OLF1) 4-46
register 2-45, 2-46, 2-47
SODR
least significant byte full (ORF) 4-42
most significant byte full (ORF1) 4-46
software reset (SRST) 4-48
source I/O memory enable (SIOM) 4-67
special cycle command 2-4
SREQ 2-42
SREQ/ status (REQ) 4-39
SSEL/ status (SEL) 4-39
SSTAT0 2-25
SSTAT1 2-25
stacked interrupts 2-41
start
address 5-13, 5-21
DMA operation (STD) 4-72
SCSI transfer (SST) 4-25
sequence (START) 4-21
static block move selector (SBMS) 4-102
STEST2 register 2-23
STOP command 2-9
stop signal 3-6

Index

STOP/ signal 3-6
store 2-22
stress ratings 6-2
subsystem ID 2-51
subsystem ID (SID) 4-11
subsystem vendor ID 2-51
subsystem vendor ID (SVID) 4-10
SVID 2-51
SWIDE register 2-46, 2-47
SXFER 2-36
SYNC_IRQD (SI) 4-51
synchronous
data transfer rates 2-34
operation 2-34
SCSI receive 2-31
SCSI send 2-30
synchronous clock conversion factor (SCF[2:0]) 4-29
system signals 3-4

T
table indirect 5-19
mode 5-18
table relative 5-20
target
mode 5-9, 5-14
SATN/ active (M/A) 4-76
mode (TRG) 4-22
ready 3-6
timing 6-13
TCK 3-12
TDI 3-12
TDO 3-12
TEMP register 5-35
temporary (TEMP) 4-57
test interface signals 3-12
TEST_HSC/ 3-12
TEST_RST/ 3-12
third dword 5-35
timer test mode (TTM) 4-92
TMS 3-12
TolerANT 1-4, 6-5
enable (TE) 4-91
technology 1-4
benefits 1-4
electrical characteristics 6-5
totem pole output 3-3
transfer
control 2-22
control instructions 5-25
and SCRIPTS instruction prefetching 2-22
counter 5-12, 5-33
information 2-17
rate
synchronous 2-34
TRDY/ 2-9, 3-6
TRST/ 3-12

U
Ultra SCSI 1-3
benefits 1-3
clock conversion factor bits 4-29
designing an Ultra SCSI system 2-20
enable (USE) 4-28

IX-9

Ultra SCSI (Cont.)
single-ended transfers
20.0 Mbytes (16-bit transfers)
quadrupled 40 MHz clock 6-56
20.0 Mbytes (8-bit transfers)
40 MHz clock 6-56
synchronous data transfers 2-36
unexpected disconnect (UDC) 4-74, 4-78
updated address (UA) 4-105
upper register address line (A7) 5-23
use data8/SFBR 5-22

V
VDD 3-13
-A 3-13
-core 3-13
vendor
ID (VID) 4-2
unique enhancement, bit 1 (VUE1) 4-27
unique enhancements, bit 0 (VUE0) 4-27
version (VER[2:0]) 4-16
VSS 3-13
-A 3-13
-core 3-13

W
wait
disconnect instruction 5-17
for a disconnect 2-17
for valid phase 5-31
reselect instruction 5-17
select instruction 5-15
wide SCSI
chained block moves 2-44
receive (WSR) 4-28
receive bit 2-46
send (WSS) 4-27
send bit 2-45
won arbitration (WOA) 4-43
write
read instructions 5-22
read system memory from SCRIPTS 5-34
write and invalidate
enable (WIE) 4-4
enable (WRIE) 4-57
WSR bit 2-46
WSS flag 2-45

IX-10

Index

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Name
Telephone

Date
Fax

Title
Department
Company Name
Street
City, State, Zip

Customer Feedback

Mail Stop

U.S. Distributors
by State

A. E.

Avnet Electronics

http://www.hh.avnet.com

B. M.

Bell Microproducts,
Inc. (for HAB’s)

http://www.bellmicro.com

I. E.

Insight Electronics

http://www.insight-electronics.com

W. E.

Wyle Electronics

http://www.wyle.com

Alabama
Daphne
I. E.
Tel: 334.626.6190
Huntsville
A. E.
Tel: 256.837.8700
B. M.
Tel: 256.705.3559
I. E.
Tel: 256.830.1222
W. E.
Tel: 800.964.9953
Alaska
A. E.
Tel: 800.332.8638
Arizona
Phoenix
A. E.
Tel: 480.736.7000
B. M.
Tel: 602.267.9551
W. E.
Tel: 800.528.4040
Tempe
I. E.
Tel: 480.829.1800
Tucson
A. E.
Tel: 520.742.0515
Arkansas
W. E.
Tel: 972.235.9953
California
Agoura Hills
B. M.
Tel: 818.865.0266
Granite Bay
B. M.
Tel: 916.523.7047
Irvine
A. E.
Tel: 949.789.4100
B. M.
Tel: 949.470.2900
I. E.
Tel: 949.727.3291
W. E.
Tel: 800.626.9953
Los Angeles
A. E.
Tel: 818.594.0404
W. E.
Tel: 800.288.9953
Sacramento
A. E.
Tel: 916.632.4500
W. E.
Tel: 800.627.9953
San Diego
A. E.
Tel: 858.385.7500
B. M.
Tel: 858.597.3010
I. E.
Tel: 800.677.6011
W. E.
Tel: 800.829.9953
San Jose
A. E.
Tel: 408.435.3500
B. M.
Tel: 408.436.0881
I. E.
Tel: 408.952.7000
Santa Clara
W. E.
Tel: 800.866.9953
Woodland Hills
A. E.
Tel: 818.594.0404
Westlake Village
I. E.
Tel: 818.707.2101

Colorado
Denver
A. E.
Tel: 303.790.1662
B. M.
Tel: 303.846.3065
W. E. Tel: 800.933.9953
Englewood
I. E.
Tel: 303.649.1800
Idaho Springs
B. M.
Tel: 303.567.0703

Illinois
North/South
A. E.
Tel: 847.797.7300
Tel: 314.291.5350
Chicago
B. M.
Tel: 847.413.8530
W. E.
Tel: 800.853.9953
Schaumburg
I. E.
Tel: 847.885.9700

Connecticut
Cheshire
A. E.
Tel: 203.271.5700
I. E.
Tel: 203.272.5843
Wallingford
W. E. Tel: 800.605.9953

Indiana
Fort Wayne
I. E.
Tel: 219.436.4250
W. E.
Tel: 888.358.9953
Indianapolis
A. E.
Tel: 317.575.3500

Delaware
North/South
A. E.
Tel: 800.526.4812
Tel: 800.638.5988
B. M.
Tel: 302.328.8968
W. E. Tel: 856.439.9110

Iowa
W. E.
Tel: 612.853.2280
Cedar Rapids
A. E.
Tel: 319.393.0033

Florida
Altamonte Springs
B. M.
Tel: 407.682.1199
I. E.
Tel: 407.834.6310
Boca Raton
I. E.
Tel: 561.997.2540
Bonita Springs
B. M.
Tel: 941.498.6011
Clearwater
I. E.
Tel: 727.524.8850
Fort Lauderdale
A. E.
Tel: 954.484.5482
W. E. Tel: 800.568.9953
Miami
B. M.
Tel: 305.477.6406
Orlando
A. E.
Tel: 407.657.3300
W. E. Tel: 407.740.7450
Tampa
W. E. Tel: 800.395.9953
St. Petersburg
A. E.
Tel: 727.507.5000
Georgia
Atlanta
A. E.
Tel: 770.623.4400
B. M.
Tel: 770.980.4922
W. E. Tel: 800.876.9953
Duluth
I. E.
Tel: 678.584.0812
Hawaii
A. E.
Tel: 800.851.2282
Idaho
A. E.
W. E.

Tel: 801.365.3800
Tel: 801.974.9953

Kansas
W. E.
Tel: 303.457.9953
Kansas City
A. E.
Tel: 913.663.7900
Lenexa
I. E.
Tel: 913.492.0408
Kentucky
W. E.
Tel: 937.436.9953
Central/Northern/ Western
A. E.
Tel: 800.984.9503
Tel: 800.767.0329
Tel: 800.829.0146
Louisiana
W. E.
Tel: 713.854.9953
North/South
A. E.
Tel: 800.231.0253
Tel: 800.231.5775
Maine
A. E.
W. E.

Tel: 800.272.9255
Tel: 781.271.9953

Maryland
Baltimore
A. E.
Tel: 410.720.3400
W. E.
Tel: 800.863.9953
Columbia
B. M.
Tel: 800.673.7461
I. E.
Tel: 410.381.3131
Massachusetts
Boston
A. E.
Tel: 978.532.9808
W. E.
Tel: 800.444.9953
Burlington
I. E.
Tel: 781.270.9400
Marlborough
B. M.
Tel: 800.673.7459
Woburn
B. M.
Tel: 800.552.4305

Michigan
Brighton
I. E.
Tel: 810.229.7710
Detroit
A. E.
Tel: 734.416.5800
W. E. Tel: 888.318.9953
Clarkston
B. M.
Tel: 877.922.9363
Minnesota
Champlin
B. M.
Tel: 800.557.2566
Eden Prairie
B. M.
Tel: 800.255.1469
Minneapolis
A. E.
Tel: 612.346.3000
W. E. Tel: 800.860.9953
St. Louis Park
I. E.
Tel: 612.525.9999
Mississippi
A. E.
Tel: 800.633.2918
W. E. Tel: 256.830.1119
Missouri
W. E. Tel: 630.620.0969
St. Louis
A. E.
Tel: 314.291.5350
I. E.
Tel: 314.872.2182
Montana
A. E.
Tel: 800.526.1741
W. E. Tel: 801.974.9953
Nebraska
A. E.
Tel: 800.332.4375
W. E. Tel: 303.457.9953
Nevada
Las Vegas
A. E.
Tel: 800.528.8471
W. E. Tel: 702.765.7117
New Hampshire
A. E.
Tel: 800.272.9255
W. E. Tel: 781.271.9953
New Jersey
North/South
A. E.
Tel: 201.515.1641
Tel: 609.222.6400
Mt. Laurel
I. E.
Tel: 856.222.9566
Pine Brook
B. M.
Tel: 973.244.9668
W. E. Tel: 800.862.9953
Parsippany
I. E.
Tel: 973.299.4425
Wayne
W. E. Tel: 973.237.9010
New Mexico
W. E. Tel: 480.804.7000
Albuquerque
A. E.
Tel: 505.293.5119

U.S. Distributors
by State
(Continued)
New York
Hauppauge
I. E.
Tel: 516.761.0960
Long Island
A. E.
Tel: 516.434.7400
W. E.
Tel: 800.861.9953
Rochester
A. E.
Tel: 716.475.9130
I. E.
Tel: 716.242.7790
W. E.
Tel: 800.319.9953
Smithtown
B. M.
Tel: 800.543.2008
Syracuse
A. E.
Tel: 315.449.4927
North Carolina
Raleigh
A. E.
Tel: 919.859.9159
I. E.
Tel: 919.873.9922
W. E.
Tel: 800.560.9953
North Dakota
A. E.
Tel: 800.829.0116
W. E.
Tel: 612.853.2280
Ohio
Cleveland
A. E.
Tel: 216.498.1100
W. E.
Tel: 800.763.9953
Dayton
A. E.
Tel: 614.888.3313
I. E.
Tel: 937.253.7501
W. E.
Tel: 800.575.9953
Strongsville
B. M.
Tel: 440.238.0404
Valley View
I. E.
Tel: 216.520.4333
Oklahoma
W. E.
Tel: 972.235.9953
Tulsa
A. E.
Tel: 918.459.6000
I. E.
Tel: 918.665.4664
Oregon
Beaverton
B. M.
Tel: 503.524.1075
I. E.
Tel: 503.644.3300
Portland
A. E.
Tel: 503.526.6200
W. E.
Tel: 800.879.9953
Pennsylvania
Mercer
I. E.
Tel: 412.662.2707
Philadelphia
A. E.
Tel: 800.526.4812
B. M.
Tel: 877.351.2355
W. E.
Tel: 800.871.9953
Pittsburgh
A. E.
Tel: 412.281.4150
W. E.
Tel: 440.248.9996
Rhode Island
A. E.
800.272.9255
W. E.
Tel: 781.271.9953

South Carolina
A. E.
Tel: 919.872.0712
W. E. Tel: 919.469.1502
South Dakota
A. E.
Tel: 800.829.0116
W. E. Tel: 612.853.2280
Tennessee
W. E. Tel: 256.830.1119
East/West
A. E.
Tel: 800.241.8182
Tel: 800.633.2918
Texas
Arlington
B. M.
Tel: 817.417.5993
Austin
A. E.
Tel: 512.219.3700
B. M.
Tel: 512.258.0725
I. E.
Tel: 512.719.3090
W. E. Tel: 800.365.9953
Dallas
A. E.
Tel: 214.553.4300
B. M.
Tel: 972.783.4191
W. E. Tel: 800.955.9953
El Paso
A. E.
Tel: 800.526.9238
Houston
A. E.
Tel: 713.781.6100
B. M.
Tel: 713.917.0663
W. E. Tel: 800.888.9953
Richardson
I. E.
Tel: 972.783.0800
Rio Grande Valley
A. E.
Tel: 210.412.2047
Stafford
I. E.
Tel: 281.277.8200
Utah
Centerville
B. M.
Tel: 801.295.3900
Murray
I. E.
Tel: 801.288.9001
Salt Lake City
A. E.
Tel: 801.365.3800
W. E. Tel: 800.477.9953
Vermont
A. E.
Tel: 800.272.9255
W. E. Tel: 716.334.5970
Virginia
A. E.
Tel: 800.638.5988
W. E. Tel: 301.604.8488
Haymarket
B. M.
Tel: 703.754.3399
Springfield
B. M.
Tel: 703.644.9045

Washington
Kirkland
I. E.
Tel: 425.820.8100
Maple Valley
B. M.
Tel: 206.223.0080
Seattle
A. E.
Tel: 425.882.7000
W. E.
Tel: 800.248.9953
West Virginia
A. E.
Tel: 800.638.5988
Wisconsin
Milwaukee
A. E.
Tel: 414.513.1500
W. E.
Tel: 800.867.9953
Wauwatosa
I. E.
Tel: 414.258.5338
Wyoming
A. E.
Tel: 800.332.9326
W. E.
Tel: 801.974.9953

Direct Sales
Representatives by State
(Component and HAB)
E. A.
E. L.
GRP
I. S.
ION
R. A.
SGY

Earle Associates
Electrodyne - UT
Group 2000
Infinity Sales, Inc.
ION Associates, Inc.
Rathsburg Associates, Inc.
Synergy Associates,
Inc.

Arizona
Tempe
E. A.
Tel: 480.921.3305
California
Calabasas
I. S.
Tel: 818.880.6480
Irvine
I. S.
Tel: 714.833.0300
San Diego
E. A.
Tel: 619.278.5441
Illinois
Elmhurst
R. A.
Tel: 630.516.8400
Indiana
Cicero
R. A.
Tel: 317.984.8608
Ligonier
R. A.
Tel: 219.894.3184
Plainfield
R. A.
Tel: 317.838.0360
Massachusetts
Burlington
SGY
Tel: 781.238.0870
Michigan
Byron Center
R. A.
Tel: 616.554.1460
Good Rich
R. A.
Tel: 810.636.6060
Novi
R. A.
Tel: 810.615.4000
North Carolina
Cary
GRP
Tel: 919.481.1530
Ohio
Columbus
R. A.
Tel: 614.457.2242
Dayton
R. A.
Tel: 513.291.4001
Independence
R. A.
Tel: 216.447.8825
Pennsylvania
Somerset
R. A.
Tel: 814.445.6976

Texas
Austin
ION
Tel: 512.794.9006
Arlington
ION
Tel: 817.695.8000
Houston
ION
Tel: 281.376.2000
Utah
Salt Lake City
E. L.
Tel: 801.264.8050
Wisconsin
Muskego
R. A.
Tel: 414.679.8250
Saukville
R. A.
Tel: 414.268.1152

Sales Offices and Design
Resource Centers

LSI Logic Corporation
Corporate Headquarters
1551 McCarthy Blvd
Milpitas CA 95035

Tel: 408.433.8000
Fax: 408.433.8989

Fort Collins
2001 Danfield Court
Fort Collins, CO 80525

Tel: 970.223.5100
Fax: 970.206.5549

New Jersey
Red Bank
125 Half Mile Road
Suite 200
Red Bank, NJ 07701

Tel: 732.933.2656
Fax: 732.933.2643

NORTH AMERICA

Florida
Boca Raton

Cherry Hill - Mint Technology

California
Irvine

2255 Glades Road
Suite 324A
Boca Raton, FL 33431

Tel: 561.989.3236
Fax: 561.989.3237

Tel: 856.489.5530
Fax: 856.489.5531

Georgia
Alpharetta

New York
Fairport

2475 North Winds Parkway
Suite 200
Alpharetta, GA 30004

550 Willowbrook Office Park
Fairport, NY 14450

18301 Von Karman Ave
Suite 900
Irvine, CA 92612

♦ Tel: 949.809.4600

Fax: 949.809.4444
Pleasanton Design Center
5050 Hopyard Road, 3rd Floor
Suite 300
Pleasanton, CA 94588

Tel: 925.730.8800
Fax: 925.730.8700

Tel: 770.753.6146
Fax: 770.753.6147
Illinois
Oakbrook Terrace

215 Longstone Drive
Cherry Hill, NJ 08003

Tel: 716.218.0020
Fax: 716.218.9010
North Carolina
Raleigh
Phase II
4601 Six Forks Road
Suite 528
Raleigh, NC 27609

Tel: 630.954.2234
Fax: 630.954.2235

Tel: 919.785.4520
Fax: 919.783.8909

Kentucky
Bowling Green

Oregon
Beaverton

1551 McCarthy Blvd
Sales Office
M/S C-500
Milpitas, CA 95035

1262 Chestnut Street
Bowling Green, KY 42101

15455 NW Greenbrier Parkway
Suite 235
Beaverton, OR 97006

Fax: 408.954.3353

Maryland
Bethesda

7585 Ronson Road
Suite 100
San Diego, CA 92111

Tel: 858.467.6981
Fax: 858.496.0548
Silicon Valley

♦ Tel: 408.433.8000
Design Center
M/S C-410
Tel: 408.433.8000
Fax: 408.433.7695

Wireless Design Center
11452 El Camino Real
Suite 210
San Diego, CA 92130

Tel: 858.350.5560
Fax: 858.350.0171
Colorado
Boulder
4940 Pearl East Circle
Suite 201
Boulder, CO 80301

♦ Tel: 303.447.3800

Fax: 303.541.0641
Colorado Springs

Tel: 270.793.0010
Fax: 270.793.0040

6903 Rockledge Drive
Suite 230
Bethesda, MD 20817

Tel: 301.897.5800
Fax: 301.897.8389
Massachusetts
Waltham
200 West Street
Waltham, MA 02451

♦ Tel: 781.890.0180

Fax: 781.890.6158

Tel: 503.645.0589
Fax: 503.645.6612
Texas
Austin
9020 Capital of TX Highway North
Building 1
Suite 150
Austin, TX 78759

Tel: 512.388.7294
Fax: 512.388.4171
Plano
500 North Central Expressway
Suite 440
Plano, TX 75074

♦ Tel: 972.244.5000

Burlington - Mint Technology

Fax: 972.244.5001

77 South Bedford Street
Burlington, MA 01803

Houston

Tel: 781.685.3800
Fax: 781.685.3801

20405 State Highway 249
Suite 450
Houston, TX 77070

4420 Arrowswest Drive
Colorado Springs, CO 80907

Minnesota
Minneapolis

Tel: 719.533.7000
Fax: 719.533.7020

8300 Norman Center Drive
Suite 730
Minneapolis, MN 55437

♦ Tel: 612.921.8300

Fax: 612.921.8399

260 Hearst Way
Suite 400
Kanata, ON K2L 3H1

♦ Tel: 613.592.1263

Fax: 613.592.3253

Two Mid American Plaza
Suite 800
Oakbrook Terrace, IL 60181

San Diego

Canada
Ontario
Ottawa

Tel: 281.379.7800
Fax: 281.379.7818

INTERNATIONAL
France
Paris
LSI Logic S.A.
Immeuble Europa
53 bis Avenue de l'Europe
B.P. 139
78148 Velizy-Villacoublay
Cedex, Paris

♦ Tel: 33.1.34.63.13.13

Fax: 33.1.34.63.13.19
Germany
Munich
LSI Logic GmbH
Orleansstrasse 4
81669 Munich

♦ Tel: 49.89.4.58.33.0

Fax: 49.89.4.58.33.108
Stuttgart
Mittlerer Pfad 4
D-70499 Stuttgart

♦ Tel: 49.711.13.96.90

Fax: 49.711.86.61.428
Italy
Milan
LSI Logic S.P.A.
Centro Direzionale Colleoni Palazzo
Orione Ingresso 1
20041 Agrate Brianza, Milano

♦ Tel: 39.039.687371

Fax: 39.039.6057867
Japan
Tokyo
LSI Logic K.K.
Rivage-Shinagawa Bldg. 14F
4-1-8 Kounan
Minato-ku, Tokyo 108-0075

♦ Tel: 81.3.5463.7821

Fax: 81.3.5463.7820
Osaka
Crystal Tower 14F
1-2-27 Shiromi
Chuo-ku, Osaka 540-6014

♦ Tel: 81.6.947.5281

Fax: 81.6.947.5287

Sales Offices and Design
Resource Centers
(Continued)
Korea
Seoul
LSI Logic Corporation of
Korea Ltd
10th Fl., Haesung 1 Bldg.
942, Daechi-dong,
Kangnam-ku, Seoul, 135-283

Tel: 82.2.528.3400
Fax: 82.2.528.2250
The Netherlands
Eindhoven
LSI Logic Europe Ltd
World Trade Center Eindhoven
Building ‘Rijder’
Bogert 26
5612 LZ Eindhoven

Tel: 31.40.265.3580
Fax: 31.40.296.2109
Singapore
Singapore
LSI Logic Pte Ltd
7 Temasek Boulevard
#28-02 Suntec Tower One
Singapore 038987

Tel: 65.334.9061
Fax: 65.334.4749
Sweden
Stockholm
LSI Logic AB
Finlandsgatan 14
164 74 Kista

♦ Tel: 46.8.444.15.00

Fax: 46.8.750.66.47
Taiwan
Taipei
LSI Logic Asia, Inc.
Taiwan Branch
10/F 156 Min Sheng E. Road
Section 3
Taipei, Taiwan R.O.C.

Tel: 886.2.2718.7828
Fax: 886.2.2718.8869
United Kingdom
Bracknell
LSI Logic Europe Ltd
Greenwood House
London Road
Bracknell, Berkshire RG12 2UB

♦ Tel: 44.1344.426544

Fax: 44.1344.481039

♦ Sales Offices with

Design Resource Centers

International Distributors

Australia
New South Wales
Reptechnic Pty Ltd

Hong Kong
Hong Kong
AVT Industrial Ltd

3/36 Bydown Street
Neutral Bay, NSW 2089

Unit 608 Tower 1
Cheung Sha Wan Plaza
833 Cheung Sha Wan Road
Kowloon, Hong Kong

♦ Tel: 612.9953.9844

Fax: 612.9953.9683
Belgium
Acal nv/sa
Lozenberg 4
1932 Zaventem

Tel: 32.2.7205983
Fax: 32.2.7251014
China
Beijing
LSI Logic International
Services Inc.
Beijing Representative
Office
Room 708
Canway Building
66 Nan Li Shi Lu
Xicheng District
Beijing 100045, China

Tel: 86.10.6804.2534 to 38
Fax: 86.10.6804.2521
France
Rungis Cedex
Azzurri Technology France
22 Rue Saarinen
Sillic 274
94578 Rungis Cedex

Tel: 33.1.41806310
Fax: 33.1.41730340
Germany
Haar
EBV Elektronik

Tel: 852.2428.0008
Fax: 852.2401.2105
Serial System (HK) Ltd
2301 Nanyang Plaza
57 Hung To Road, Kwun Tong
Kowloon, Hong Kong

Tel: 852.2995.7538
Fax: 852.2950.0386
India
Bangalore
Spike Technologies India
Private Ltd
951, Vijayalakshmi Complex,
2nd Floor, 24th Main,
J P Nagar II Phase,
Bangalore, India 560078

♦ Tel: 91.80.664.5530

Fax: 91.80.664.9748

Macnica Corporation

Tel: 44.1628.826826
Fax: 44.1628.829730

Hakusan High-Tech Park
1-22-2 Hadusan, Midori-Ku,
Yokohama-City, 226-8505

Milton Keynes
Ingram Micro (UK) Ltd

Tel: 81.45.939.6140
Fax: 81.45.939.6141
The Netherlands
Eindhoven
Acal Nederland b.v.

Japan
Tokyo
Daito Electron

Tel: 49.89.4600980
Fax: 49.89.46009840
Munich
Avnet Emg GmbH

Global Electronics
Corporation

Stahlgruberring 12
81829 Munich

Nichibei Time24 Bldg. 35 Tansu-cho
Shinjuku-ku, Tokyo 162-0833

Tel: 49.89.45110102
Fax: 49.89.42.27.75

Tel: 81.3.3260.1411
Fax: 81.3.3260.7100
Technical Center
Tel: 81.471.43.8200

Tel: 81.3.5778.8662
Fax: 81.3.5778.8669
Shinki Electronics
Myuru Daikanyama 3F
3-7-3 Ebisu Minami
Shibuya-ku, Tokyo 150-0022

Tel: 81.3.3760.3110
Fax: 81.3.3760.3101

Tel: 44.1908.260422
Swindon
EBV Elektronik

Tel: 31.40.2.502602
Fax: 31.40.2.510255

12 Interface Business Park
Bincknoll Lane
Wootton Bassett,
Swindon, Wiltshire SN4 8SY

Switzerland
Brugg
LSI Logic Sulzer AG
Mattenstrasse 6a
CH 2555 Brugg

14F, No. 145,
Sec. 2, Chien Kuo N. Road
Taipei, Taiwan, R.O.C.

Tel: 886.2.2516.7303
Fax: 886.2.2505.7391
Lumax International
Corporation, Ltd
7th Fl., 52, Sec. 3
Nan-Kang Road
Taipei, Taiwan, R.O.C.

Tel: 886.2.2788.3656
Fax: 886.2.2788.3568
Prospect Technology
Corporation, Ltd
4Fl., No. 34, Chu Luen Street
Taipei, Taiwan, R.O.C.

Tel: 886.2.2721.9533
Fax: 886.2.2773.3756

Marubeni Solutions
1-26-20 Higashi
Shibuya-ku, Tokyo 150-0001

Garamonde Drive
Wymbush
Milton Keynes
Buckinghamshire MK8 8DF

Beatrix de Rijkweg 8
5657 EG Eindhoven

Taiwan
Taipei
Avnet-Mercuries
Corporation, Ltd

Tel: 81.3.3264.0326
Fax: 81.3.3261.3984

Tel: 49.2957.79.1692
Fax: 49.2957.79.9341

Tel: 81.45.474.9037
Fax: 81.45.474.9065

11 Rozanis Street
P.O. Box 39300
Tel Aviv 61392

Tel: 972.3.6458777
Fax: 972.3.6458666

United Kingdom
Maidenhead
Azzurri Technology Ltd
16 Grove Park Business Estate
Waltham Road
White Waltham
Maidenhead, Berkshire SL6 3LW

Tel: 41.32.3743232
Fax: 41.32.3743233

Sogo Kojimachi No.3 Bldg
1-6 Kojimachi
Chiyoda-ku, Tokyo 102-8730

Graf-Zepplin-Str 14
D-33181 Wuennenberg-Haaren

2-15-10 Shin Yokohama
Kohoku-ku
Yokohama-City, 222-8580

Israel
Tel Aviv
Eastronics Ltd

Hans-Pinsel Str. 4
D-85540 Haar

Wuennenberg-Haaren
Peacock AG

Yokohama-City
Innotech

Wintech Microeletronics
Co., Ltd
7F., No. 34, Sec. 3, Pateh Road
Taipei, Taiwan, R.O.C.

Tel: 886.2.2579.5858
Fax: 886.2.2570.3123

Tel: 44.1793.849933
Fax: 44.1793.859555

♦ Sales Offices with

Design Resource Centers

Source Exif Data:

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Keywords                        : LSI8953U..SCSI Technology..PCI Express
Modify Date                     : 2005:01:05 12:56:16-08:00
Create Date                     : 2000:12:06 14:53:11Z
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Metadata Date                   : 2005:01:05 12:56:16-08:00
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Format                          : application/pdf
Title                           : LSI53C875A PCI to Ultra SCSI Controller technical manual
Description                     : This document provides complete functional descriptions, electrical specifications, and physical characteristics for the LSI53C875A PCI to Ultra SCSI I/O processor. The LSI53C875A enables the connection of Ultra SCSI drives to a host system through a PCI bus. Ultra SCSI is an extension of the SCSI-3 specification that supports transfers of up to 20 Mbytes/s. The LSI53C875A supports a 32-bit PCI bus with 64-bit DAC addressing.
Creator                         : FrameMaker 5.5.6p145
Subject                         : This document provides complete functional descriptions, electrical specifications, and physical characteristics for the LSI53C875A PCI to Ultra SCSI I/O processor. The LSI53C875A enables the connection of Ultra SCSI drives to a host system through a PCI bus. Ultra SCSI is an extension of the SCSI-3 specification that supports transfers of up to 20 Mbytes/s. The LSI53C875A supports a 32-bit PCI bus with 64-bit DAC addressing.

EXIF Metadata provided by EXIF.tools

Lsi 53C875A Users Manual LSI53C875A PCI To Ultra SCSI Controller Technical

53C875A to the manual 90e6953d-57eb-48c2-a2fc-d40073dc3ec7

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