Original SFF 8020i Specification SFF8020i

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Small Form Factor Committee
Specification of

ATA Packet Interface for CD-ROMs

Revision 2.6 Proposed
January 22, 1996

Status: Review Copy

SFF-8020i

Member Companies Supporting This Specification:
Adaptec
Aztech Systems
Cirrus Logic
Compaq
Conner Peripherals
Dell
ENDL
Fujitsu Microelectronics
IBM

Intel
Maxtor
Microsoft
Mitsumi
Molex
National Semiconductor
NEC
OAK Technologies
Philips LMS

Quantum
Sanyo
Seagate Technology
Silicon Systems
Sony
Wearnes Technology
Western Digital

Member Companies Voting Against This Specification:

Point of Contact:I. Dal Allan
Chairman SFF Committee
ENDL
14426 Black Walnut Court
Saratoga, CA 95070
Ph: (408) 867-6630
Fax: (408) 867-2115
E-Mail: 250-1752@mcimail.com
SFF FaxAccess: (408) 741-1600

Technical Editors:Tom Hanan
Western Digital Corporation
8105 Irvine Center Drive
Irvine Calif. 92718
Ph: (714) 932-7472
Fax: (714) 932-7312
E-Mail: hanan_t@a1.wdc.com
Devon Worrell
Western Digital Corporation
8105 Irvine Center Drive
Irvine Calif 92718
Ph: (714) 932-7042
Fax: (714) 932-7796
E-Mail: worrell@dt.wdc.com

The following member companies of the SFF Committee voted in favor of this industry
specification.
3M
AMP
Aztech Systems
Berg
Cirrus Logic
Compaq
DEC
Dell
ENDL
Fujitsu Microelectronics
Hitachi America
Honda Connector
IBM
Integral Peripherals
Intel
Madison Cable
Methode
Microsoft
Mitsumi
Molex
National Semiconductor
NEC Electronics
Oak Technology
Philips LMS
Robinson Nugent
Sanyo
Sigmax
Sony
Sun Microsystems
Wearnes Peripherals
Western Digital

The following member companies of the SFF Committee voted against this industry
specification.
Adaptec
Conner Peripherals
Maxtor
Quantum
Silicon Systems

The following member companies of the SFF Committee voted to forward this
industry specification to an accredited standards body.
Adaptec
Cirrus Logic
Dell
ENDL
Fujitsu Microelectronics
Maxtor
Methode
National Semiconductor
Oak Technology
Quantum
Robinson Nugent
Silicon Systems
Wearnes Peripherals

ATAPI CD-ROM Specification

Table of Contents
January 22, 1996

Table of Contents
1.0

2.0

3.0

Page 1

Introduction . . . . . . . . . . . . . . . . . . . .
1.1
Abstract. . . . . . . . . . . . . . . . . .
1.2
Secretariat . . . . . . . . . . . . . . . .
1.3
Summary of SFF Principals . . . . . . .
1.4
SFF Membership and Fees . . . . . . . .
1.5
Scope . . . . . . . . . . . . . . . . . . .
1.6
Audience . . . . . . . . . . . . . . . . .
1.7
Normative References . . . . . . . . . .
1.8
Prerequisites and Related Documents . .
1.9
Layout of the Document . . . . . . . . .
1.10
Patents . . . . . . . . . . . . . . . . . .
1.11
Unresolved Issues . . . . . . . . . . . .
1.12
Change History. . . . . . . . . . . . . .
General. . . . . . . . . . . . . . . . . . . . . . .
2.1
Overview . . . . . . . . . . . . . . . . .
2.2
Feature Summary. . . . . . . . . . . . .
Conventions . . . . . . . . . . . . . . . . . . . .
3.1
Document Conventions . . . . . . . . .
3.2
Signal Conventions. . . . . . . . . . . .
3.3
Definitions . . . . . . . . . . . . . . . .
3.3.1
Absolute F Field . . . . . . . .
3.3.2
Absolute M Field . . . . . . . .
3.3.3
Absolute S Field . . . . . . . .
3.3.4
ATA (AT Attachment) . . . . .
3.3.5
BCD . . . . . . . . . . . . . .
3.3.6
Block . . . . . . . . . . . . . .
3.3.7
Blocks Per Sector . . . . . . . .
3.3.8
CD-DA . . . . . . . . . . . . .
3.3.9
CD-ROM . . . . . . . . . . . .
3.3.10 CD-ROM Control Field . . . .
3.3.11 CD-ROM Data Mode. . . . . .
3.3.12 Changer . . . . . . . . . . . . .
3.3.13 CHS (Cylinder-Head-Sector) . .
3.3.14 CIRC . . . . . . . . . . . . . .
3.3.15 Command Packet (CP) . . . . .
3.3.16 Data Block . . . . . . . . . . .
3.3.17 DMA (Direct Memory Access).
3.3.18 Field . . . . . . . . . . . . . .
3.3.19 Frame . . . . . . . . . . . . . .
3.3.20 Hold Track State . . . . . . . .
3.3.21 Index . . . . . . . . . . . . . .
3.3.22 Invalid . . . . . . . . . . . . .
3.3.23 LBA (Logical Block Address) .
3.3.24 Logical Block . . . . . . . . . .
3.3.25 Lead-in Area . . . . . . . . . .
3.3.26 Lead-out Area . . . . . . . . .
3.3.27 L-EC . . . . . . . . . . . . . .
3.3.28 LUN . . . . . . . . . . . . . .
3.3.29 Mandatory . . . . . . . . . . .
3.3.30 MSF Address . . . . . . . . . .
3.3.31 One . . . . . . . . . . . . . . .
3.3.32 Optional. . . . . . . . . . . . .

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.1
.1
.1
.2
.3
.4
.4
.4
.5
.5
.6
.6
.6
.9
.9
.9
11
11
11
11
11
11
11
12
12
12
12
12
12
12
12
12
13
13
13
13
13
13
13
13
13
13
14
14
14
14
14
14
14
14
14
14

working draft ATAPI

ATAPI CD-ROM Specification

Table of Contents
January 22, 1996

Table of Contents

4.0

5.0

Page 2

3.3.33 Output Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.34 Page . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.35 Pause Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.36 PIO (Programmed Input/Output) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.37 Post-gap Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.38 Pre-gap Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.39 Relative F Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.40 Relative M Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.41 Relative S Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.42 SAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.43 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3.44 Sector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.45 Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.46 Sub-channel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.47 TOC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.48 Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.49 Transition Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.50 VU (Vendor Unique) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.51 Zero . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.4
Symbols and Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
ATAPI Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1
ATA Signal Utilization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.2
ATA Command Utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.3
ATA Compatibility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.4
Packet Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.5
How SCSI is Used by ATAPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.5.1
Differences from the SCSI Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.5.2
Redundant Command Functionality (Task File vs. Packet) . . . . . . . . . . . . . . . . 20
4.5.2.1
Door Lock and Door Unlock vs. Prevent / Allow Medium Removal . . . . . 20
4.5.2.2
ATAPI Identify Drive vs. Inquiry . . . . . . . . . . . . . . . . . . . . . . . 20
4.5.2.3
Initialize Drive Parameters and Set Features vs. Mode Sense and Mode Select 20
ATAPI Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.1
Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.2
ATAPI PACKET Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.3
Status Register Utilization for Packet Commands . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.4
Byte Count Register (Cylinder Low/High) Usage for Packet Commands. . . . . . . . . . . . . . 22
5.5
Sector Count (ATAPI Interrupt Reason) Register Usage for Packet Commands . . . . . . . . . . 23
5.6
Immediate Command Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.7
Overlapped Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.7.1
Example of ATAPI Overlap with only one ATAPI Peripheral . . . . . . . . . . . . . . 24
5.8
Flow of Packet Command, PIO Data In to Host . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.9
Flow of Overlapped Commands with Data Transfer In to Host . . . . . . . . . . . . . . . . . . . 27
5.10
Flow of Packet Command with PIO Data Out from the Host . . . . . . . . . . . . . . . . . . . . 30
5.11
Flow of Overlapped Commands with Data Transfer Out From Host . . . . . . . . . . . . . . . . 32
5.12
Flow of Non-Overlap DMA Data Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.13
Flow of Non-data Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.14
Timing of Non-Overlap Packet Command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.15
Timing of Non-Overlap Data and Status Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.16
Control Signal Timing Requirements and Relationships . . . . . . . . . . . . . . . . . . . . . . 38
5.17
Overlapped Command Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.17.1 Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.17.2 Service Command (A2h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

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Table of Contents
January 22, 1996

Table of Contents

6.0

7.0

Page 3

5.17.3 Overlapped Operation, Legal Transitions . . . . . . . . . . . . . . . . . . . . . . . . .
5.17.4 Task File ownership . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.17.5 Error Handling with Overlapped Commands . . . . . . . . . . . . . . . . . . . . . . .
5.18
BIOS and ATAPI Driver Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.18.1 Reset Master/Slave Diagnostics Sequence . . . . . . . . . . . . . . . . . . . . . . . . .
5.18.2 SRST Initialization Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.18.2.1 SRST Sequence Device 0 . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.18.2.2 SRST Sequence Device 1 . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.18.2.3 Other SRST Related Issues . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.18.3 Special Handling of ATA Read and Identify Drive Commands . . . . . . . . . . . . . .
5.18.4 ATAPI aware BIOS and Driver Considerations . . . . . . . . . . . . . . . . . . . . . .
5.18.5 Default Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ATAPI Transport Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1
Reset Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1.1
Power On or Hardware Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2
ATAPI Soft Reset Command and Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3
ATAPI Implementation of ATA SRST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4
Physical Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5
Single Drive Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.6
Register Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.7
ATAPI Register Map (Packet Command) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CD-ROM ATA (Task File) Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1
ATA (Task File) Command Implementation Requirements . . . . . . . . . . . . . . . . . . . . .
7.1.1
ATAPI Soft Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.2
Check Power Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.3
Execute Drive Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.4
Idle Immediate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.5
NOP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.6
Packet Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.7
ATAPI Identify Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.7.1
General Configuration Word (0) . . . . . . . . . . . . . . . . . . . . . . . .
7.1.7.2
Serial Number (Words 10 - 19). . . . . . . . . . . . . . . . . . . . . . . . .
7.1.7.3
Firmware Revision (Words 23-26) . . . . . . . . . . . . . . . . . . . . . . .
7.1.7.4
Model Number (Words 27 - 46) . . . . . . . . . . . . . . . . . . . . . . . .
7.1.7.5
Capabilities Word (Word 49). . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.7.6
PIO Data Transfer Cycle Timing (Word 51) . . . . . . . . . . . . . . . . . .
7.1.7.7
DMA Data Transfer Cycle Timing (Word 52) . . . . . . . . . . . . . . . . .
7.1.7.8
Field Validity (Word 53) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.7.9
Single Word DMA Transfer (Word 62) . . . . . . . . . . . . . . . . . . . .
7.1.7.10 Multi Word DMA Transfer (Word 63) . . . . . . . . . . . . . . . . . . . . .
7.1.7.11 Enhanced PIO Mode (Word 64) . . . . . . . . . . . . . . . . . . . . . . . .
7.1.7.12 Minimum Multi-word DMA Transfer Cycle Time per Word (Word 65) . . .
7.1.7.13 Manufacturer’s Recommended Multi-word DMA Cycle Time (Word 66) . .
7.1.7.14 Minimum PIO Transfer Cycle Time Without Flow Control (Word 67) . . . .
7.1.7.15 Minimum PIO Transfer Cycle Time with IORDY Flow Control (Word 68) .
7.1.7.16 Typical Time for the Release After Command Received (Word 71) . . . . .
7.1.7.17 Typical Time for the Clearing of Busy After SERVICE Command (Word 72)
7.1.7.18 Major Version Number (Word 73) . . . . . . . . . . . . . . . . . . . . . . .
7.1.7.19 Minor Version Number (Word 74) . . . . . . . . . . . . . . . . . . . . . . .
7.1.8
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.9
Set Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.9.1
Set Transfer Mode (03h) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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47
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49
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52
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60
60
61
61
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8.0

9.0

10.0

Page 4

7.1.9.2
Enable Interrupt for Release after receipt of Command Packet (5Dh) .
7.1.9.3
Enable Interrupt After Completion of Service Command (5Eh) . . . .
7.1.9.4
Disable Reverting to Power On Defaults (66h) . . . . . . . . . . . .
7.1.9.5
Enable Reverting to Power On Defaults (CCh) . . . . . . . . . . . .
7.1.9.6
Disable Interrupt for Release after receipt of Command Packet (DDh)
7.1.9.7
Disable Interrupt After Completion of Service Command (DEh) . . .
7.1.10 Sleep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.11 Standby Immediate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CD-ROM Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.1
New Capabilities Since the SCSI-2 Standardization. . . . . . . . . . . . . . . . . . . . .
8.2
CD-ROM Media Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.3
CD-ROM Physical Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.3.1
Frame Format for Audio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.3.2
Sector Format for Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.3.3
Sub-channel Information Formats . . . . . . . . . . . . . . . . . . . . . . . . .
8.4
CD Audio Error Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.5
CD-ROM Ready Condition/Not Ready Condition. . . . . . . . . . . . . . . . . . . . . .
8.5.1
Packet Command Not Ready Status Utilization . . . . . . . . . . . . . . . . . .
8.6
CD-ROM Address Reporting Formats (MSF bit) . . . . . . . . . . . . . . . . . . . . . .
8.7
Error Reporting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Changer Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.1
Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2
Changer Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.3
Automatic Load and Unload Operations. . . . . . . . . . . . . . . . . . . . . . . . . . .
9.4
Delayed Disc load operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.5
Prevent / Allow processing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.6
Error Reporting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CD-ROM Packet Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.1
Packet Command Implementation Requirements . . . . . . . . . . . . . . . . . . . . . .
10.1.1 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.1.2 Operation Code Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2
ATAPI Command Packet Description . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.1 Operation Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.2 Logical Block Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.3 Transfer Length. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.4 Parameter List Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.5 Allocation Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.3
Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.4
Immediate Command Processing Considerations . . . . . . . . . . . . . . . . . . . . . .
10.5
Command Processing Considerations and Exception Conditions . . . . . . . . . . . . . .
10.5.1 Parameter Rounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.6
Unit Attention Condition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.7
Commands and Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8
ATAPI Packet Commands for CD-ROM Devices . . . . . . . . . . . . . . . . . . . . . .
10.8.1 INQUIRY Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.1.1 Standard INQUIRY Data . . . . . . . . . . . . . . . . . . . . . . .
10.8.1.2 Using the INQUIRY Command . . . . . . . . . . . . . . . . . . . .
10.8.2 LOAD/UNLOAD CD Command . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.3 MECHANISM STATUS Command . . . . . . . . . . . . . . . . . . . . . . . .
10.8.4 MODE SELECT Command . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.5 MODE SENSE Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.5.1 Current Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Table of Contents
January 22, 1996

Table of Contents

11.0

10.8.5.2 Changeable Values . . . . . . . . . . . . . . . . . . . . . .
10.8.5.3 Default Values . . . . . . . . . . . . . . . . . . . . . . . .
10.8.5.4 Saved Values . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.5.5 Initial Responses . . . . . . . . . . . . . . . . . . . . . . .
10.8.6 Mode Select/Sense Parameters . . . . . . . . . . . . . . . . . . . . . .
10.8.6.1 CD-ROM Audio Control Parameters Page . . . . . . . . . .
10.8.6.2 CD-ROM Device Parameters Page. . . . . . . . . . . . . .
10.8.6.3 Read Error Recovery Parameters Page . . . . . . . . . . . .
10.8.6.4 CD-ROM Capabilities and Mechanical Status Page . . . . .
10.8.7 PAUSE/RESUME Command . . . . . . . . . . . . . . . . . . . . . .
10.8.8 PLAY AUDIO Command . . . . . . . . . . . . . . . . . . . . . . . .
10.8.8.1 Play Audio with Immediate Packet Commands . . . . . . .
10.8.9 PLAY AUDIO MSF Command . . . . . . . . . . . . . . . . . . . . .
10.8.10 PLAY CD Command . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.11 PREVENT/ALLOW MEDIUM REMOVAL Command . . . . . . . .
10.8.12 READ (10) Command . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.13 READ (12) Command . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.14 READ CD-ROM CAPACITY Command . . . . . . . . . . . . . . . .
10.8.15 READ CD Command. . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.15.1 Description of Sub-channels R-W . . . . . . . . . . . . . .
10.8.16 READ CD MSF Command. . . . . . . . . . . . . . . . . . . . . . . .
10.8.17 READ HEADER Command . . . . . . . . . . . . . . . . . . . . . . .
10.8.18 READ SUB-CHANNEL Command . . . . . . . . . . . . . . . . . . .
10.8.18.1 CD-ROM Current Position Data Format . . . . . . . . . . .
10.8.18.2 Media Catalogue Number Data Format . . . . . . . . . . .
10.8.18.3 Track International Standard Recording Code Data Format .
10.8.18.4 Caching of Sub-Channel Data . . . . . . . . . . . . . . . .
10.8.19 READ TOC Command . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.19.1 Sub-channel Q TOC information . . . . . . . . . . . . . . .
10.8.19.2 Example Read TOC Operations . . . . . . . . . . . . . . .
10.8.20 REQUEST SENSE Command . . . . . . . . . . . . . . . . . . . . . .
10.8.20.1 Sense-key Specific . . . . . . . . . . . . . . . . . . . . . .
10.8.20.2 Deferred Errors . . . . . . . . . . . . . . . . . . . . . . . .
10.8.20.3 Sense-key and Sense Code Definitions. . . . . . . . . . . .
10.8.20.4 Using the REQUEST SENSE Command . . . . . . . . . .
10.8.21 SCAN Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.22 SEEK Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.23 SET CD SPEED Command . . . . . . . . . . . . . . . . . . . . . . .
10.8.24 STOP PLAY / SCAN CD-ROM Command . . . . . . . . . . . . . . .
10.8.25 START/STOP UNIT Command . . . . . . . . . . . . . . . . . . . . .
10.8.26 TEST UNIT READY Command . . . . . . . . . . . . . . . . . . . . .
10.8.26.1 Using the TEST UNIT READY Command . . . . . . . . .
Physical Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.1
CD-ROM Digital Audio Connector (Optional) . . . . . . . . . . . . . . . . . .
11.2
CD-ROM Analog Audio Connector (Optional) . . . . . . . . . . . . . . . . . .
11.3
Device Configuration Jumper (Optional) . . . . . . . . . . . . . . . . . . . . .
11.4
Host IDE Interface Connector . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.5
Power Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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.106
.106
.106
.106
.108
.111
.113
.114
.118
.123
.125
.126
.128
.131
.135
.137
.139
.141
.143
.151
.155
.157
.161
.162
.165
.166
.168
.169
.175
.177
.179
.181
.182
.183
.183
.187
.191
.193
.195
.197
.199
.199
.201
.201
.201
.202
.202
.202

Annex A Play CD Decoder Types & Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
Annex B Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205

Page 5

working draft ATAPI

Revision 2.6 Proposed
January 22, 1996 2:58 pm

Intentionally Left Blank

Page 6

working draft ATAPI

ATAPI CD-ROM Specification

List of Tables
January 22, 1996

List of Tables
Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Table 10 Table 11 Table 12 Table 13 Table 14 Table 15 Table 16 Table 17 Table 18 Table 19 Table 20 Table 21 Table 22 Table 23 Table 24 Table 25 Table 26 Table 27 Table 28 Table 29 Table 30 Table 31 Table 32 Table 33 Table 34 Table 35 Table 36 Table 37 Table 38 Table 39 Table 40 Table 41 Table 42 Table 43 Table 44 Table 45 Table 46 Table 47 Table 48 Table 49 Table 50 Table 51 Table 52 -

Page 7

Layout of the Document. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Generic Command and Status Usage for ATAPI Devices . . . . . . . . . . . .
Byte Count Register Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Registers after the Service Command . . . . . . . . . . . . . . . . . . . . . . .
Legal Transitions for Overlapped Operation . . . . . . . . . . . . . . . . . . .
Registers Controlled by BSY & DRQ. . . . . . . . . . . . . . . . . . . . . . .
Preferred Drive Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shadow Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shadowing for Single Drive Configurations . . . . . . . . . . . . . . . . . . .
I/O Port Functions/Selection Addresses (Compatibility Model) . . . . . . . . .
ATAPI Status Register (ATA Status Register) . . . . . . . . . . . . . . . . . .
ATAPI Error Register (ATA Error Register) . . . . . . . . . . . . . . . . . . .
ATAPI Feature Register (ATA Feature Register). . . . . . . . . . . . . . . . .
ATAPI Byte Count Register (ATA Cylinder High/Low Register) . . . . . . . .
ATAPI Interrupt Reason Register (ATA Sector Count Register). . . . . . . . .
ATAPI Drive Select Register (ATA Drive / Head Select Register) . . . . . . .
ATAPI Device Control Register (ATA Device Control Register) . . . . . . . .
ATA Command and Status Usage for ATAPI CD-ROM Devices . . . . . . . .
Identify Drive, Fields Supported by CD-ROM . . . . . . . . . . . . . . . . . .
Identify Drive Data - General Configuration (Word 0) . . . . . . . . . . . . . .
Identify Drive Data - Capabilities Word (49) . . . . . . . . . . . . . . . . . . .
Contents of the Feature Register for Set Features Command . . . . . . . . . . .
Set Feature Register Definitions . . . . . . . . . . . . . . . . . . . . . . . . .
Feature Number Description for Set Feature Command . . . . . . . . . . . . .
Example Mixed Mode CD-ROM Disc Layout . . . . . . . . . . . . . . . . . .
Not Ready Error Reporting (by Command) . . . . . . . . . . . . . . . . . . . .
MSF Address Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Error Conditions and Sense Keys . . . . . . . . . . . . . . . . . . . . . . . . .
Commands that may cause delayed loads to occur . . . . . . . . . . . . . . . .
Commands that will cause delayed loads to occur . . . . . . . . . . . . . . . .
Commands that should not cause delayed loads to occur . . . . . . . . . . . . .
Error Conditions and Sense Keys for Changer Mechanisms . . . . . . . . . . .
Operation Code Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Typical Command Packet for Most Commands . . . . . . . . . . . . . . . . .
Typical Command Packet for Some Extended Commands . . . . . . . . . . . .
Operation Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Packet Commands Supported by CD-ROM Drives . . . . . . . . . . . . . . . .
INQUIRY Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
INQUIRY Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Peripheral Device Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Inquiry Command Errors. . . .
Load / Unload Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Load/Unload or Optional Selection Operations . . . . . . . . . . . . . . . . . .
recommended Sense Key, ASC and ASCQ for Load / Unload CD. . . . . . . .
MECHANISM STATUS Command . . . . . . . . . . . . . . . . . . . . . . .
Mechanism Status Parameter List . . . . . . . . . . . . . . . . . . . . . . . . .
Mechanism Status Header . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Slot Table Response format . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Mechanism Status . . . . . . .
Mode Select Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Mode Select Command Errors .
Mode Sense command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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. .5
. 18
. 23
. 41
. 42
. 45
. 52
. 52
. 53
. 54
. 55
. 55
. 56
. 56
. 57
. 57
. 57
. 59
. 62
. 63
. 65
. 68
. 68
. 69
. 72
. 78
. 78
. 79
. 83
. 84
. 84
. 84
. 87
. 88
. 88
. 89
. 92
. 93
. 94
. 94
. 95
. 97
. 97
. 98
. 99
.100
.100
.101
.102
.103
.104
.105

working draft ATAPI

ATAPI CD-ROM Specification

List of Tables
January 22, 1996

List of Tables
Table 53 Table 54 Table 55 Table 56 Table 57 Table 58 Table 59 Table 60 Table 61 Table 62 Table 63 Table 64 Table 65 Table 66 Table 67 Table 68 Table 69 Table 70 Table 71 Table 72 Table 73 Table 74 Table 75 Table 76 Table 77 Table 78 Table 79 Table 80 Table 81 Table 82 Table 83 Table 84 Table 85 Table 86 Table 87 Table 88 Table 89 Table 90 Table 91 Table 92 Table 93 Table 94 Table 95 Table 96 Table 97 Table 98 Table 99 Table 100 Table 101 Table 102 Table 103 Table 104 -

Page 8

Page Control Field. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Mode Sense Command Errors . . .
Mode Parameter List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mode Page Codes for CD-ROM . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mode Page Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mode Parameter Header. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CD-ROM Media Type Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CD-ROM Audio Control Mode Page Format . . . . . . . . . . . . . . . . . . . . .
CDDA Output Port Channel Selection Codes. . . . . . . . . . . . . . . . . . . . .
Attenuation Levels for Audio . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CD-ROM Parameters Page Format . . . . . . . . . . . . . . . . . . . . . . . . . .
Inactivity Time Multiplier Values. . . . . . . . . . . . . . . . . . . . . . . . . . .
Read Error Recovery Parameters Page Format . . . . . . . . . . . . . . . . . . . .
Error Recovery Bit Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CD-ROM Error Recovery Descriptions . . . . . . . . . . . . . . . . . . . . . . . .
CD-ROM Capabilities and Mechanical Status Page Format . . . . . . . . . . . . .
Example Data Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PAUSE/RESUME Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Pause/Resume Command Errors . .
PLAY AUDIO Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Play Audio Command Errors . . .
Commands That Will Stop a Play or Scan Operation . . . . . . . . . . . . . . . . .
Commands That Will Not Stop a Play or Scan Operation . . . . . . . . . . . . . .
PLAY AUDIO MSF Command . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Play Audio MSF Command Errors
PLAY CD Command (LBA Form) . . . . . . . . . . . . . . . . . . . . . . . . . .
PLAY CD Command (MSF Form) . . . . . . . . . . . . . . . . . . . . . . . . . .
PLAY CD, Expected Sector Type Field Definition . . . . . . . . . . . . . . . . . .
PLAY CD, Field Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for PLAY CD Command Errors . . . .
PREVENT ALLOW MEDIUM REMOVAL Command . . . . . . . . . . . . . . .
Actions for Lock / Unlock / Eject . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Prevent/Allow Command Errors . .
READ (10) Command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for READ (10) Command Errors . . .
READ (12) Command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for READ (10) Command Errors . . .
READ CD-ROM CAPACITY Command . . . . . . . . . . . . . . . . . . . . . .
READ CAPACITY DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Read Capacity Command Errors . .
READ CD Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
READ-CD, Expected Sector Type Field Definition . . . . . . . . . . . . . . . . .
READ CD, Header(s) Code Field Definition . . . . . . . . . . . . . . . . . . . . .
READ CD, Error Flag(s) Field Definition . . . . . . . . . . . . . . . . . . . . . .
READ CD, Sub-channel Data Selection Field Definition . . . . . . . . . . . . . .
Formatted Q-subcode Data (A Total of 16 Bytes) . . . . . . . . . . . . . . . . . .
Number of Bytes Returned Based on Data Selection Field . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Read CD Command Errors. . . . .
CD-DA (Digital Audio) Data Block Format . . . . . . . . . . . . . . . . . . . . .
R-W Raw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
R-W De-Interleaved & Error Corrected. . . . . . . . . . . . . . . . . . . . . . . .
Sub-channel R-W, Allowed Mode/Item Combinations . . . . . . . . . . . . . . . .

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working draft ATAPI

ATAPI CD-ROM Specification

List of Tables
January 22, 1996

List of Tables
Table 105 Table 106 Table 107 Table 108 Table 109 Table 110 Table 111 Table 113 Table 112 Table 114 Table 115 Table 116 Table 117 Table 118 Table 119 Table 120 Table 121 Table 122 Table 123 Table 124 Table 125 Table 126 Table 127 Table 128 Table 129 Table 130 Table 131 Table 132 Table 133 Table 134 Table 135 Table 136 Table 137 Table 138 Table 139 Table 140 Table 141 Table 142 Table 143 Table 144 Table 145 Table 146 Table 147 Table 148 Table 149 Table 150 Table 151 Table 152 Table 153 Table 154 Table 155 Table 156 -

Page 9

READ CD MSF Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Read CD MSF Command Errors. . . . . .
READ HEADER Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
READ HEADER LBA Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
READ HEADER MSF Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CD-ROM Data Mode Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Read Header Command Errors. . . . . . .
Sub-channel Data Header Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
READ SUB-CHANNEL Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sub-channel Data Format Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CD-ROM Current Position Data Format (Format Code 01h). . . . . . . . . . . . . . . . .
Audio Status Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ADR Sub-channel Q Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sub-channel Q Control Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Media Catalogue Number Data Format (Format Code 02h) . . . . . . . . . . . . . . . . .
UPC Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Track International Standard Recording Code Data Format . . . . . . . . . . . . . . . . .
Raw ISRC Format on the CD-ROM Disc . . . . . . . . . . . . . . . . . . . . . . . . . . .
ISRC Format of Data Returned to Host . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Read Sub-channel Command Errors . . . .
READ TOC Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Read TOC Data Format (With Format Field = 00b) . . . . . . . . . . . . . . . . . . . . .
Read TOC Data Format (With Format Field = 01b) . . . . . . . . . . . . . . . . . . . . .
Read TOC Data Format (With Format Field = 10b) . . . . . . . . . . . . . . . . . . . . .
TOC Track Descriptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Read TOC Command Errors . . . . . . . .
Lead in Area (TOC), Sub-channel Q formats . . . . . . . . . . . . . . . . . . . . . . . . .
Bit Definitions for the Control Field in Sub-channel Q . . . . . . . . . . . . . . . . . . . .
Values for Control Field in Sub-channel Q . . . . . . . . . . . . . . . . . . . . . . . . . .
Example Read TOC Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Values for Control Field in Read TOC . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Request Sense Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Request Sense Standard Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Field Pointer Bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Field Pointer Bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sense Key Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ASC and ASCQ Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Request Sense Command Errors . . . . . .
SCAN Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Scan Starting Address in Logical Block Format . . . . . . . . . . . . . . . . . . . . . . .
Scan Starting Address in AMIN, ASEC and AFRAME Format . . . . . . . . . . . . . . .
Scan Starting Address in Track Number (TNO) Format . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Scan Command Errors . . . . . . . . . . .
SEEK Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for Seek Command Errors . . . . . . . . . . .
SET CD-ROM SPEED Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for SET CD SPEED Command Errors . . . .
STOP PLAY / SCAN CD-ROM Command . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Sense Key, ASC and ASCQ for STOP PLAY CD-ROM Command Errors .
START/STOP UNIT Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Start/Stop and Eject Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Actions for Eject/Load Disc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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.185
.187
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.188
.189
.191
.191
.193
.193
.195
.195
.197
.197
.198

working draft ATAPI

Revision 2.6 Proposed
January 22, 1996 2:57 pm
Table 157 - Recommended Sense Key, ASC and ASCQ for SEEK Command Errors . . . . . . . . . . . . . . . . .198
Table 158 - Test Unit Ready Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199
Table 159 - Recommended Sense Key, ASC and ASCQ for MODE SELECT Command Errors . . . . . . . . . . .200

Page 10

working draft ATAPI

ATAPI CD-ROM Specification

List of Figures
January 22, 1996

List of Figures
Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 -

Page 11

Example ATAPI Overlap Command Sequence . . . . . . . . .
Packet Command with PIO Data In to Host. . . . . . . . . . .
Overlapped Packet Command with PIO Data In to Host . . . .
Packet Command with PIO Data Out from Host . . . . . . . .
Overlapped Packet Command with PIO Data Out From Host .
Timing of Command Packet Transfer . . . . . . . . . . . . . .
Timing of Data and Status Transfer . . . . . . . . . . . . . . .
State Diagram, Overlapped Operation . . . . . . . . . . . . .
ATAPI Overlap, One ATA Device and One ATAPI Device . .
DASP / PDIAG Sequence after Hardware Reset or Power On .
CD-ROM Sector Formats . . . . . . . . . . . . . . . . . . . .
Changer State Diagram . . . . . . . . . . . . . . . . . . . . .
Read CD Data Stream Order . . . . . . . . . . . . . . . . . .
Read CD Sub-channel, R-W (100b). . . . . . . . . . . . . . .
Stop Play/Play Audio/Audio Scan/Pause/Resume Sequencing .
Test Unit Ready State Diagram . . . . . . . . . . . . . . . . .
CD-ROM Connectors (Rear View) . . . . . . . . . . . . . . .
Device Configuration Jumper . . . . . . . . . . . . . . . . . .

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working draft ATAPI

Revision 2.6 Proposed
January 22, 1996 2:57 pm

Intentionally Left Blank

Page 12

working draft ATAPI

ATAPI CD-ROM Specification
Introduction

1.0 Introduction
The ATA/IDE interface has become a de facto industry standard for connection of disk drives in PC‘s. In the interest of
simplicity and cost, the ATA/IDE interface was originally designed to support only a small subset of computer peripherals. The expanding use of multimedia, inexpensive program distribution on CD ROM, and faster and more powerful systems has created the need for enhancements to ATA. This specification is one of those enhancements and provides a
simple and inexpensive CD-ROM interface through a superset of ATA.

1.1 Abstract
This document defines a standard method for interfacing to a CD-ROM Drive utilizing the existing ATA host computer
hardware and cabling. This specification supplements the definitions of an ATA mass storage peripheral found in the
ATA document. The ATAPI and CD-ROM interfaces described in this document are compatible with existing ATA hardware without any changes or additional pins.

1.2 Secretariat
The SFF Committee is an ad hoc group formed to address disk industry needs in a prompt manner. When formed in
1990, the original goals were limited to defining de facto mechanical envelopes for disk drives so they
could fit into laptop computers and other small products.
In November 1992, the SFF Committee objectives were broadened to encompass areas other than mechanical form factors for drives, which needed prompt industry action. SFF Specifications are narrow in scope, to reduce development
time.
The SFF Committee complements the formal standards process. Some industry needs cannot be addressed by standards
because of timing, or charter, or some other consideration. This is a gap the Small Form Factor Committee fills.
It is anticipated that most Specifications will be Forwarded to an accredited standards body such as EIA (Electronic Industries Association) or ASC (Accredited Standards Committee) X3T10. They may be accepted for separate standards, or
incorporated into other standards activities.
The members decision to forward is based on a wide variety of factors, and a document can be forwarded at any stage in
its development cycle. For example, if a proposal is under development within SFF, and a standards project begins in a
similar area. The SFF members might submit the draft of the SFF Specification to the standards committee rather than
operate a parallel effort.
In the case of proposals submitted to SFF which now have a status of Fs, the proposal never became an SFF project or
specification. Instead the proposal was forwarded to the appropriate standards body for further consideration. A copy of
the proposal submitted to SFF remains available for historical purposes, however, the contents may no longer be valid.
The latest documentation for forwarded SFF specifications should be obtained from the committee the proposal was forwarded to. The best way to track standards activity is to subscribe to the document service for X3T10 subcommittees:
CBEMA X3 Secretariat:
1250 Eye St. #200
Washington DC 20005

Ph: 202-737-8888
Fax: 202-638-4922

Copies of SFF Specifications are available by FaxAccess or by joining the SFF Committee as an Observer ($300 or $400
overseas) or Member ($3,000).
14426 Black Walnut Ct
Saratoga CA 95070

working draft ATAPI

Ph: 408-867-6630x303
Fax: 408-867-2115

Email: 250-1752@mcimail.com
FaxAccess: 408-741-1600

Page 1

Revision 2.6 Proposed
January 18, 1996 12:12 pm

Introduction
Summary of SFF Principals

1.3 Summary of SFF Principals
Documents created by the SFF Committee are expected to be submitted to accredited standards bodies such as EIA
(Electronic Industries Association) or ASC (Accredited Standards Committee) X3T10. They may be accepted for separate standards, or incorporated into other standards activities. The principles of operation for the SFF Committee are not
unlike those of an accredited standards committee. There are 3 levels of participation:
- Attending the meetings is open to all, but taking part in discussions is limited to member companies, or those invited by
member companies.
- The minutes and copies of material which are discussed during meetings are distributed only to those who sign up to
receive documentation.
- The individuals who represent member companies of the SFF Committee receive documentation and vote on issues
that arise. Votes are not taken during meetings, only guidance on directions. All voting is by letter ballot, which ensures
all members an equal opportunity to be heard.
Material presented at SFF Committee meetings becomes public domain. There are no restrictions on the open mailing of
material presented at committee meetings. In order to reduce disagreements and misunderstandings, copies must be provided for all agenda items that are discussed. Copies of the material presented, or revisions if completed in time, are included in the documentation mailings.
The sites for SFF Committee meetings rotate based on which member companies volunteer to host the meetings. For information on meeting dates and places, subscribe to the SFF E-mail reflector.

Page 2

working draft ATAPI

ATAPI CD-ROM Specification
Introduction
1.4 SFF Membership and Fees
The funds received from the annual membership fees are placed in escrow, and are used to reimburse ENDL for the services to manage the SFF Committee.
Annual SFF Committee Membership Fee
Annual SFF Committee Documentation Fee
Annual Surcharge for AIR MAIL to Overseas

$1,800.00
$300.00
$100.00

Funds received will be retained in escrow until earned and will be
accounted for to the members of the SFF Committee.
To join SFF, fill out the form below and indicate the method of payment.
Name:

_______________________________

Title:

_______________________________

Company:

_______________________________

Address:

_______________________________
_______________________________
_______________________________

Phone:

_______________________________

Fax:

_______________________________

Email:

_______________________________

Please register me as the company representative on the SFF
Committee ($2,100 or $2,200 overseas fee includes documentation).
Check Payable to SFF Committee is Enclosed: ____
Please Invoice me: ___ PO #: __________________
Signature: _____________________________________

Please register me to receive documentation on activities of the SFF Committee.
Check Payable to SFF Committee:
(POs Not Accepted)

U.S.
Overseas

$300.00
$400.00

Signature: _____________________________________
Fax POs to: 408 867-2115

working draft ATAPI

Mail Checks to:
.....................

14426 Black Walnut Ct.
Saratoga, CA 95070

Page 3

Revision 2.6 Proposed
January 18, 1996 12:12 pm

Introduction
Scope

1.5 Scope
This document is intended to be used with the ATA document. Its purpose is to highlight those areas of implementation in
which the CD-ROM Interface and the ATA document differ. In addition, it indicates areas within the ATA document
which are modified for operation in the CD-ROM environment. Both mandatory and optional specifications are presented.
In the event of a conflict between one of the base documents (ATA / SCSI CD-ROM) and this document, the interpretation of this document shall prevail only if this document acknowledges that a conflict exists between the documents.
This document provides a description for the ATAPI Transport Protocol (TP), ATAPI Transport Mechanism (TM) as well
as a CD-ROM Command Protocol (CP).

CD-ROM Commands

ATA Commands

Other Commands
Commands

ATA Task File

ATAPI
Transport Protocol (TP)
Protocols

ATA Hardware

ATAPI
Transport Mechanism (TM)

PCMCIA
Interconnects

1.6 Audience
This document is intended for use by Computer System, CD-ROM Peripheral, and CD-ROM chip set vendors.

1.7 Normative References
The following standards contain provisions which, when referenced in the text of this standard, constitute provisions of
this Specification. At the time of publication, the editions indicated were valid. All standards are subject to revision, and
parties to agreements based on this Specification are encouraged to investigate the possibility of applying the most recent
editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International
Standards.
ISO/IEC 10149:1989, Information technology - Data Interchange on Read-only 120 mm Optical Data Disks.
IEC 908:1987, Compact Disk Digital Audio System.
American National Standard Institute X3.131-1994, Small Computer System Interface.
American National Standard Institute X3T10/948D ATA-2 (AT Attachment).

Page 4

working draft ATAPI

ATAPI CD-ROM Specification
Introduction
1.8 Prerequisites and Related Documents
The reader is expected to have a basic understanding of the AT hardware and software interfaces as well as the ATA Document. Specifically, the following documents are required for understanding and implementing an ATA CD-ROM because this document is based on them:
•

CBEMA, ATA (AT Attachment) ANSI Draft Standard, Revision 9482K, December 2, 1994, Document Number X3T10/948, Computer and Business Equipment Manufacturer’s Association. This
is referred to as the ATA Document.

•

ANSI X3T9.2/375R, Small Computer System Interface

•

AT bus specification

•

Red, Yellow, Green, Orange Books and CD-ROM XA Specification.

1.9 Layout of the Document
This document is broken into several sections:

Table 1 - Layout of the Document
Section "1.0 Introduction" on page 1

Introduction, scope, purpose etc.

SFF-8021

Section "2.0 General" on page 9

Details the current requirements, assumptions and goals.

Section "3.0 Conventions" on page 11

Describes conventions used in the document, and a definitions of terms and signals.

Section "4.0 ATAPI Overview" on page 17

Overview of the Packet Interface and how
the “Layering” of SCSI and ATA occurs.

Section "5.0 ATAPI Protocol" on page 21

Describes the actual “Protocol” used for
the new Packet Command.

Section "6.0 ATAPI Transport Mechanism" on page 49

Describes ATAPI register and hardware
usage of the ATA Interface.

section 8.0, "CD-ROM Model", on page 71

Overview and general comments on CDROM device functions and media formats.

section 7.0, "CD-ROM ATA (Task File) Commands", on page 59

ATA Task File Command set definition for
the CD-ROM peripheral type.

Section "10.0 CD-ROM Packet Commands" on page 87

SCSI Command Subset definition for the
CD-ROM peripheral type.

SFF-8024

Section "11.0 Physical Interface" on page 201

Describes the physical Host Interface,
connectors and their placement.

SFF-8025

Annex “A” Digital Output
Annex “B” Connectors

Provides informative reference material
which will very likely be implemented by
some CD-ROM manufacturers.

SFF-8026
SFF-8027

Annex “C” Errata sheet for SFF-8020 rev 2.x

Identifies current editorial & technical corrections made to SFF-8020 rev 2.x.

SFF-8028

SFF-8022

SFF-8023

To simplify retrieval of this document via the SFF FaxAccess system, the individual sections of this document are available as individual SFF FaxAccess documents. Unless you have a plain paper fax machine with the ability to print 300
pages in a single fax, you should request the individual sections. Request SFF-8020 to receive the entire document or request any of the numbers between 8021 and 8028 to receive the individual section(s) identified in the table above.

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Introduction
Patents

1.10 Patents
The developers of this specification have requested that holders of patents that may be required for the implementation
of the specification, disclose such patents to the publisher. However, neither the developers nor the publisher have undertaken a patent search in order to identify which, if any, patents apply to this specification.
No position is taken with respect to the validity of any claim or any patent rights that may have been disclosed. Details
of submitted statements may be obtained from the publisher concerning any statement of patents and willingness to
grant a license under these rights on reasonable and nondiscriminatory terms and conditions to applicants desiring to obtain such a license.

1.11 Unresolved Issues
This section identifies issues which are still unresolved. Refer to E-mail on the ATAPI Reflector (atapi@dt.wdc.com) for
details on each of the issues identified below: Note at this time there are no unresolved issues.

1.12 Change History
SFF 8020 r1.2 was published in February 1994. This has become the defacto industry standard.
After the version 1.2 was published, corrections were made through the use of an errata document. The 8020 and 8029
were used together as a document set. Many changes to 8029 Errata for 8020 r1.2 between March 1994 and March 1995
were made.
1.2 to 2.0 Early 1995.
•

All Errata incorporated into the SFF ATAPI Document and 8029 removed from use.

2.0a to 2.1 March 1995.
•

Basic Overlap capability added.

•

Many editorial changes.

2.1 to 2.2 April 1995.
•

Proxy IRQ added.

•

Interleaved DMA added.

•

CHANGER STATUS, LOAD/UNLOAD CD added. Establishes a simple way for ATAPI tape and
CD devices to manage built in low cost CHANGER mechanisms.

2.2 to 2.3 May 1995.
•

PLAY CD added. The PLAY CD command simplifies playing audio and video to an external device (e.g. an IEC958 or EBU port).

•

Register Shadowing and Single device clarifications were added.

•

INQUIRY “Vital Product Data” and “Vital Product Data Parameters” were deleted.

•

PLAY AUDIO (12) was deleted.

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ATAPI CD-ROM Specification
Introduction
•

Read (12) was deleted.

•

PLAY AUDIO TRACK RELATIVE was deleted.

•

REZERO UNIT was removed as this command was redundant with the reset command and was
unsupported.

•

PLAY CD-ROM XA, and SEND CD-ROM XA DATA were removed. The XA Annex and all XA
commands (PLAY, SEND) were removed due to a lack of definition and support by OS and ATAPI
CD-ROM devices.

•

Vendor Identification List (Table 141) was removed since the information is contained in the SCSI
document provided as a normative reference.

•

READ CD Data Transfer Modes. Many of these modes were deleted because the group felt that
they were complicated to implemented and not required by current OS drivers.

2.3 to 2.4 July 1995
•

MECHANISM STATUS command replaces the Changer Status command. This command become mandatory for both changer and normal CD mechanisms. This command is used by non
changer mechanisms to report the current state of the device (includes playing, scanning, idle...).

•

Proxy Interrupt removed.

•

Overlapped DMA removed.

•

Interleaved DMA removed.

•

Some clarifications to the Changer commands.

•

Many small editorial and clarification changes.

2.4 to 2.5 July 1995
•

The Opcode for the MECHANISM STATUS Command has been changed from B8h to BDh.

•

The Opcode for the PLAY CD Command has been changed from B4h to BCh.

•

The READ (12) has been added back into the specification.

•

An ATAPI Version has been added to the INQUIRY Data. For conformance to ATAPI 2.5 the value
returned is 2h.

•

Further clarifications to the Changer commands were made.

•

Sub-channel data returned in the READ CD commands was limited to Audio tracks.

•

Table 26 has been rearranged and corrected.

•

Mechanism Status, CD Mechanism State information now allows the host to determine if a Play
or Read operation is in progress and if the Audio or other ports are in use.

•

The SRST will no longer require the drive to perform the DASP / PDIAG Master Slave Handshaking Protocol.

•

The Identify Drive Data was brought in line with ATA.

2.5 to 2.6 November 1995
•

Clarification of Byte Count Register Usage for Packet Commands.

•

Clarification of back-to-back data transfers

•

SRST allowed to be used during Power Management of ATAPI Devices

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Introduction
Change History

•

SRST use of the PDIAG signal is clarified

•

Clarification of error condition for truncating data when allocation is non zero.

•

Error code returned when loading a slot with no disc present has been changed from 05/24 to 02/
3A.

•

Table 65, CD-ROM Capabilities and Mechanical Status Page Format, now defines bytes 2 and 3,
for new CD media type functions.

•

Clarification of CD-ROM Medium Type Codes, Table 56.

•

Block Error Flag byte defined as the OR of all C2 Error Bytes.

•

Table 120, ISRC Format, byte definitions have been changed.

•

Added table for TOC TRACK DESCRIPTORS.

•

Section 3.3.49, Track Relative Logical Address, has been removed.

•

Bytes 2 and 3 of INQUIRY command changed to “reserved.” References to EVPD removed.

•

READ TOC command - Format field now includes Byte 2.

•

READ TOC Data Format and MSF usage clarified.

•

Back-to-back data transfers sequence description added. State diagrams updated.

•

SRST PDIAG sequence added.

•

Changer functions for delayed load have been clarified.

•

Identify Drive Data has been clarified.

•

Identify, Additional length information has been clarified.

•

Reporting of Errors for Mode Select has been clarified.

•

The SSS and SDP bits in the Mode Sense Capabilites Page have been moved.

•

Block Length returned for Read CD-ROM Capacity has been clarified.

•

Length of data returned for Read TOC commands have been clarified.

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ATAPI CD-ROM Specification
General

2.0 General
2.1 Overview
The primary objective of this Standard is to provide an inexpensive CD-ROM interface. The existing ATA does not provide an adequate command structure to support CD-ROM devices. Although the inclusion of a CD-ROM drive would
compromise the performance of another disk on the same ATA Cable, this standard does addresses this through the use of
overlapped operation.

2.2 Feature Summary
This section provides an abbreviated list of the perceived requirements upon which the development of this specification
was based.
•

Do not break any existing ATA drive connections when the CD-ROM is attached, e.g., completely compatible with existing hardware and drivers.

•

Prevent BIOS and O/S recognition of ATAPI Peripherals as hard disk drives.

•

Allow one ATA cable and I/O registers to support one ATA drive and one CD-ROM peripheral.

•

Support for the ATA master / slave protocol.

•

Support for 8-bit Task File registers and 16-bit data transfer register.

•

Reset the peripheral into a known state.

•

Provide a status indication of Peripheral Ready to accept commands.

•

Provide capability for sending CDB like (Command Packet Bytes) to the peripheral.

•

Support for command packets of at least 12 bytes in length.

•

Capability to indicate to the Host computer when Command Packet can be transferred.

•

Capability to Interrupt the Host computer when data can be transferred.

•

Capability to Interrupt the Host computer when command complete.

•

Send & Receive Data bytes using either PIO or DMA.

•

Capable of transferring variable length data packets. (Drive indicates to Host amount to transfer.)

•

Send Status of command operation (Error / Done / Data Ready...) to the host computer.

•

Enable and disable Host interrupts from the peripheral.

•

Detect when a peripheral is interrupting (Which & Why.)

•

Detect when an ATAPI peripheral is attached to the ATA Cable.

•

Support for both primary and secondary ATA addressing / cable.

•

Support for all ATA 948 data transfer timing.

•

Support for the CD-DA, CD-XA, CD +, Multi Session and Hybrid (Photo CD) formats.

•

Support for multiple speed drives.

•

Support multiple block sizes (i.e. 2048, 2052, 2056, 2324, 2332, 2336, 2340 & 2352)

•

Overlap Commands with non-overlapping ATA devices.

•

Support for Embedded Media Changers.

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General
Feature Summary

Intentionally Left Blank

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ATAPI CD-ROM Specification
Conventions

3.0 Conventions
3.1 Document Conventions
Certain words and terms used in this document have specific meaning beyond the normal English meaning. These words
and terms are defined either in this section or in the text where they first appear. Names of signals, commands, statuses,
and sense keys are in all uppercase (e.g. REQUEST SENSE). Lower case is used for words having the normal English
meaning.
Fields containing only one bit are usually referred to as the  bit instead of the  field. Numbers that are
not immediately followed by a lower case b or h are decimal (0xnn for Hexadecimal, where nn refers to two hexadecimal digits 0-9, A-F.)

3.2 Signal Conventions
Signal names are shown in all upper case letters. Signals can be asserted (active, true) in either a high (more positive voltage) or low (less positive voltage) state. A dash character (-) at the beginning or end of a signal name indicates it is asserted at the low level (active low). No dash or a plus character (+) at the beginning or end of a signal name indicates it is
asserted high (active high). An asserted signal may be driven high or low by an active circuit, or it may be allowed to be
pulled to the correct state by the bias circuitry.
Control signals that are asserted for one function when high and asserted for another function when low are named with
the asserted high function name followed by a slash character (/), and the asserted low function name followed with a
dash (-) e.g. BITENA/BITCLR- enables a bit when high and clears a bit when low. All signals are TTL-compatible unless otherwise noted. “Negated” means that the signal is driven by an active circuit to the state opposite to the asserted
state (inactive, or false) or may be simply released (in which case the bias circuitry pulls it inactive, or false) at the option of the implementor.
Control signals that may be used for two mutually exclusive functions are identified with their two names separated by a
colon e.g. SPSYNC:CSEL can be used for either the Spindle Sync or the Cable Select functions.

3.3 Definitions
3.3.1 Absolute F Field
Absolute F field is the least significant part of the absolute physical address from the beginning of the media. It is written
on CD-ROM media in binary-coded decimal notation. The value ranges from 00 to 74.

3.3.2 Absolute M Field
Absolute M field is the most significant part of the absolute physical address from the beginning of the media. It is written on CD-ROM media in binary-coded decimal notation. The value ranges from 00 to 99.

3.3.3 Absolute S Field
Absolute S field is the intermediate significant part of the absolute physical address from the beginning of the media. It
is written on CD- ROM media in binary-coded decimal notation. The value ranges from 00 to 59.

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Conventions
Definitions

3.3.4 ATA (AT Attachment)
ATA defines a compatible register set and a 40-pin connector and its associated signals.

3.3.5 BCD
Binary coded decimal: The number system used on the physical CD-ROM and CD-DA media. Numbers that use this notation have the ‘bcd’ suffix attached. A byte has two 4-bit values, each of which can have a value from 0 to 9. The maximum value is 99bcd (99 decimal). BCD is only used on the physical CD Media, and never to/from the host except when
raw sub-channel data is returned in the data to the host.
Example: 00 01 02 03... 08 09 10 11... 19 20 21... 98 99bcd.

3.3.6 Block
The term “block” refers to the data in one logical block; the number of bytes in a block is defined by the logical block
length in the mode block descriptor.

3.3.7 Blocks Per Sector
“Blocks per sector” is the number of logical blocks read from each CD-ROM physical sector. The value depends on the
logical block length as defined in the mode block descriptor.

3.3.8 CD-DA
Compact Disc-Digital Audio (CD-DA) is the standardized medium for recording digital/audio information. The ‘Red
Book’ defines CD-DA media.

3.3.9 CD-ROM
Compact Disc - Read Only Memory (CD-ROM) is the standardized medium for recording digitized audio and digital data. CD-ROM is used to describe media with digital data rather than discs that encode audio only. The ISO/IEC 10149
standard defines CD-ROM media.

3.3.10 CD-ROM Control Field
The CD-ROM Control Field is a 4-bit field in the Q sub-channel data indicating the type of information encoded on the
current track. It indicates audio versus data and the type of audio encoding, etc. The control field is also found in the table
of contents entries.

3.3.11 CD-ROM Data Mode
A byte in the header of CD-ROM data sectors. This indicates if data is present and if layered error correction information is present.

3.3.12 Changer
“Changer” is a mechanical device which allows a single physical CD-ROM drive to load and unload multiple CD-ROM
without user intervention.

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ATAPI CD-ROM Specification
Conventions
3.3.13 CHS (Cylinder-Head-Sector)
This is an ATA term defining the addressing mode of the drive as being by physical address. This form of addressing is
not used by ATAPI Devices.

3.3.14 CIRC
Cross Interleaved Reed-Solomon Code (CIRC) is the error detection and correction technique used within small frames
of audio or data. The CIRC bytes are present in all CD-ROM data modes. The error correction procedure which uses the
CIRC bytes is referred to as the CIRC based algorithm. In most CD-ROM drives, this function is implemented in hardware.

3.3.15 Command Packet (CP)
“Command Packet” is the structure used to communicate commands from a host computer to an ATAPI device.

3.3.16 Data Block
This term describes a data transfer, and is typically a single sector, except when declared otherwise by use of the Set
Multiple command.

3.3.17 DMA (Direct Memory Access)
DMA is a means of data transfer between peripheral and host memory without processor intervention.

3.3.18 Field
A field is a group of one or more contiguous bits.

3.3.19 Frame
A frame is a physical sector on CD-ROM media or the F field unit of a MSF CD-ROM address. The term frame is also
used in the CD-ROM model to describe the amount of data received between synchronization patterns. Ninety-eight
frames make a sector. This sort of frame is referred to as a ‘small frame’ when the meaning is not clear from the context.

3.3.20 Hold Track State
When a CD-ROM device enters the hold track state the optical pick-up is maintained at an approximately constant position on the media. This allows a paused operation to be resumed without latency due to seeking. However, rotational latency may be incurred.

3.3.21 Index
An index is a subdivision of a CD-ROM track. A track can have from 1 to 99 index numbers. Index numbers within a
track are sequential, starting with 1.

3.3.22 Invalid
Invalid refers to an illegal (reserved) or unsupported field or code value.

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Conventions
Definitions

3.3.23 LBA (Logical Block Address)
The LBA defines the addressing mode of the drive by the linear mapping of sectors from 0 to n.

3.3.24 Logical Block
A Logical Block is a unit of data supplied or requested by a host computer.

3.3.25 Lead-in Area
The Lead-in Area is the area on a CD-ROM disc preceding track one. The main channel in the lead-in area contains audio
or data null information. This area is coded as track zero but is not addressable via the ATA CD-ROM command set. The
Q sub-channel in this area is coded with the table of contents information.

3.3.26 Lead-out Area
The Lead-out Area is the area on a CD-ROM disc beyond the last information track. The main channel in the lead-out
area contains audio or data null information. This area is coded as track AA bcd but is not addressable via the ATA CDROM command set. The READ CD-ROM CAPACITY data is the first logical block address of this area minus one.

3.3.27 L-EC
Layered Error Correction (L-EC) is the error correction technique used with CD-ROM (data mode one) sectors. In such
sectors, 276 bytes of the auxiliary data field contain L-EC bytes. The algorithm that uses these bytes to perform error correction is often implemented in the drive firmware.

3.3.28 LUN
Logical Unit Number.

3.3.29 Mandatory
“Mandatory” indicates that a referenced item is required to claim compliance with this standard.

3.3.30 MSF Address
The MSF Address is the physical address written on CD-ROM discs. It is expressed as a sector count relative to either the
beginning of the medium (absolute) or to the beginning of the current track (relative). As defined by the CD-DA and CDROM standards, each F field unit is one physical sector; each S field unit is 75 F field units; each M field unit is 60 S field
units. Valid contents of F fields are binary values from 0 through 74. Valid contents of S fields are binary values from 0
through 59. Valid contents of M fields are binary values from 0 through 99.

3.3.31 One
“One” represents a true signal value or a true condition of a variable.

3.3.32 Optional
“Optional” describes features which are not required by the standard. However, if any feature defined by the standard is
implemented, it shall be done in the same way as defined by the standard. Describing a feature as optional in the text is
done to assist the reader. If there is a conflict between text and tables on a feature described as optional, the table shall
be accepted as being correct.

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ATAPI CD-ROM Specification
Conventions
3.3.33 Output Port
The Output Port is a means for connecting the audio signal being played to equipment outside the CD-ROM device.

3.3.34 Page
Several commands use regular parameter structures that are referred to as pages. These pages are identified with a value
known as a page code.

3.3.35 Pause Area
A “pause area” is a transition area at the beginning or end of an audio track encoded with audio silence. This transition
area is required where the audio track immediately precedes a data track.

3.3.36 PIO (Programmed Input/Output)
PIO is a means of data transfer that requires the use of the host processor.

3.3.37 Post-gap Area
Post-gap Area is a transition area at the end of a data track encoded with null information. This transition area is required
where the data track immediately precedes an audio track.

3.3.38 Pre-gap Area
Pre-gap Area is a transition area at the beginning of a data track encoded with null information. This transition area is required where the data track immediately follows an audio track.

3.3.39 Relative F Field
The sub-division of the S field part of the relative physical address from the beginning of the current track. One physical
sector. Written on CD-ROM medium in binary coded decimal notation. The value is from 00bcd to 74bcd.

3.3.40 Relative M Field
Relative M Field is the most significant part of the relative physical address from the beginning of the current track. It is
written on CD- ROM media in binary-coded decimal notation. The value is from 00bcd to 99bcd.

3.3.41 Relative S Field
Relative S Field is the intermediate significant part of the relative physical address from the beginning of the current
track. It is written on CD-ROM medium in binary-coded decimal notation. The value is from 00bcd to 59bcd.

3.3.42 SAM
SCSI Architectural Model.

3.3.43 Reserved
Reserved bits, fields, bytes, and code values are set aside for future standardization. Their use and interpretation may be
specified by future extensions to this or other standards. A reserved bit, field, or byte shall be set to zero, or in accordance
with a future extension to this standard. The recipient shall not check reserved fields.

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Conventions
Symbols and Abbreviations

3.3.44 Sector
“Sector” refers to the data contained by one frame time. (On CD-DA medium with two channels of audio this is 1/75th of
a second). In the CD-ROM standard document the term block is used for this unit. There may be more than one logical
block per sector. Similarly, a single logical block may map to multiple sectors.

3.3.45 Status
Status is one byte of information sent from the ATA CD-ROM to the host computer upon completion of each command.

3.3.46 Sub-channel
CD-ROM and CD-DA media have a main channel and a sub-channel. The sub-channel area has eight parts called P, Q, R,
S, T, U, V, and W. The Q-sub-channel contains information useful to the controller and drive, such as the control field and
MSF addresses. The data rate of each sub-channel (P, Q, etc.) is 1/192nd of that of the main channel.

3.3.47 TOC
The table of contents has information on the type of disc and the starting address of the tracks. This information is encoded in the Q sub-channel.

3.3.48 Track
A track is a sub-division of the CD-ROM media. A disc has from one to ninety-nine tracks. The data within a track is always of the same type. A track can be either CD-ROM or CD-Audio. A disc can start at any track number.

3.3.49 Transition Area
Sectors at the beginning or end of tracks that are coded with null information are called transition areas. Where required
by the media standards, these areas have minimum lengths. The maximum lengths are not specified. Transition areas at
the beginning of a track are encoded with index zero. Addresses within transition areas may not be read.

3.3.50 VU (Vendor Unique)
The term, VU, is used to describe bits, bytes, fields, code values and features which are not described in this standard,
and may be used in a way that varies between vendors.

3.3.51 Zero
Zero is a false signal value or a false condition of a variable.

3.4 Symbols and Abbreviations
LSB Least significant bit
LUN Logical unit number
MSB Most significant bit

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ATAPI CD-ROM Specification
ATAPI Overview

4.0 ATAPI Overview
The purpose of the ATAPI is to provide a more extensible and general purpose interface than the ATA Task file.
Although the attachment of a CD-ROM on the ATAPI Interface will utilize the ATA Host Hardware and Task File, the
logical interface will differ slightly and will need to support additional capabilities. The Mass Storage devices connected
to the ATA make use of eight registers (Task File) that contain the command and all parameters needed for operation.
However, eight registers is not enough to pass all the needed information for commanding other peripheral types. To
remedy this, the ATAPI Device will receive its commands through the use of a Packet mode, in addition to the normal
ATA protocol. The Packet Command will complement the existing ATA commands. The ATAPI Device shall support
all of the ATA specified protocol, including the Reset Master/Slave Diagnostic Sequence, Diagnostic Command, and
Command Abort for unsupported Commands. The ATAPI Device shall also support both the Master and Slave modes
of operation.

4.1 ATA Signal Utilization
ATAPI Devices will utilize the same signals and timing from the ATA Standard and Extensions.

4.2 ATA Command Utilization
The ATA Task File concept does not contain enough bytes to support some of the CD-ROM command structures, so a
new command called “ATAPI Packet Command” has been added to allow a Packet to be sent to the Device. The Packet
will be transferred by writing multiple times to the Data Register. No random access to the register file in the Peripheral
can be done. This technique reduces the number of register addresses needed, but not the actual space needed. Although
all the commands for the CD-ROM Device could be sent via this packet mode, some of the existing ATA commands
and the full ATA command protocol must be provided for the existing drivers to operate correctly. The CD-ROM Device will therefore support some existing ATA commands in addition to the new “ATAPI Packet command”, so that
there will be minimal changes to the existing drivers. This minimal set of ATA commands is different than the minimum
as defined in the ATA standard, but should be sufficient for normal operation.

4.3 ATA Compatibility
There are several backward compatibility issues with the existing ATA commands, and therefore the ATAPI CD-ROM
Device will respond to the existing ATA Reset Master/Slave Diagnostic Sequence, but not the Identify Drive or Read
commands. This will allow the BIOS and older drivers to ignore the CD-ROM Device and not confuse CD-ROM data
with normal ATA Drive format data. All unsupported ATA commands shall be Aborted, and not executed. As with
aborted commands in ATA, an interrupt will be generated to signal the completion with an “aborted” error status.

4.4 Packet Types
To allow for generic packet transfer and the connection of SCSI like peripherals, there shall exist a minimum set of information that is exchanged. This information shall generically support the following:
•

Command Packet (Always padded to number of bytes identified in byte 0 of the identify drive data. 00 = 12 bytes, 01 = 16 bytes)

•

Command Parameter Data (e.g. Write Data etc.)

•

Command Response Data (e.g. Read Data etc.)

•

Status. The Status will not take the form of a packet of information. The status will be presented
using the ATAPI Status Register (redefinitions of the ATA Status Register).

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ATAPI Overview
Packet Types

Table 2 - Generic Command and Status Usage for ATAPI Devices
Command

Used

Error Register

Code
BBK

Acknowledge media
change

N

Boot - post-boot

N

Boot - pre-boot

N

Check power mode

M

E5

Door lock

O

DE

UNC

IDNF

DB

ABRT

Status Register
TKONF

AMNF

DRDY

DWF

DSC

CORR

ERR

V

V

DC

V

V

DD

V

V

V

V

V

V

V

Door unlock

O

DF

V

V

Media eject

N

ED

V

V

Execute drive diags

M

90

Format track

O1

50

Identify drive

N

EC

V

Idle

O

E3

V

V

V

V

V

V

V

V
V

ATAPI Identify Device

M

A1

ATAPI Soft Reset

M

08

Service

O

Read buffer

N

V

V

91
00

V

V

E1

A0

V

V

M

M

V
V
V

N2
M

V
V

V

Idle immediate
NOP

V

Special Drive Diagnostic Errors

Initialize drive parms
ATAPI Pkt. Command

V

V
V
V
V

V

V

Contains Packet Command Status

V

V

V
V

V

V

V

V

V

A2

V

V

E4

V

V

V

Read DMA (w/retry)

N

C8

V

V

Read DMA (wo/retry)

N

C9

V

V

Read long (w/retry)

2

N

22

V

V

Read long (wo/retry)

N2

23

V

V

Read multiple

N

C4

V

V

Read sector(s) (w/retry)

N2

20

V

V

Read sector(s) (wo/retry)

N2

21

V

V

Read verify sector(s)
(w/retry)

N2

40

V

V

Read verify sector(s)
(wo/retry)

N2

41

V

V

Recalibrate

O1

1x

V

Seek

N1

7x

V

V

V

V

V

V
V

Set features

M

EF

V

V

V

V

V

Set multiple mode

N

C6

V

V

V

V

V

Sleep

M

E6

V

V

V

V

V

Standby

O

E2

V

V

V

V

V

V

V

V

V

Standby immediate

M

E0

V

Write buffer

N

E8

V

V

Write DMA (w/retry)

N

CA

V

V

Write DMA (wo/retry)

N

CB

V

V

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ATAPI CD-ROM Specification
ATAPI Overview
Table 2 - Generic Command and Status Usage for ATAPI Devices (Continued)
Command

Used

Error Register

Code
BBK

Write long (w/retry)

N2

UNC

IDNF

ABRT

Status Register
TKONF

AMNF

DRDY

DWF

DSC

CORR

ERR

32

V

V

Write long (wo/retry)

2

N

33

V

V

Write multiple

N

C5

V

V

Write same

N

E9

V

V

Write sector(s) (w/retry)

N2

30

V

V

Write sector(s) (wo/retry)

N2

31

V

V

Write verify

N

3C

V

V

Invalid command code

V

V

V

V

V

V = valid on this command
M = Mandatory and shall be supported by CD-ROM ATAPI Devices, as specified by the ATA Standard
O = Optional for use by an ATAPI Device
N = Not supported by ATAPI Devices (shall be Aborted by the ATAPI Device)
Shaded = Commands are utilized by the ATAPI Devices

1.
2.

Although this command is Optional for ATAPI the ATA Standard specifies it as Mandatory.
This command is specified as Mandatory for ATA, but shall NOT be supported by ATAPI Devices.

4.5 How SCSI is Used by ATAPI
Although the ATAPI Device will utilize many of the actual packet definitions from the SCSI standard, it will NOT use
most other features of the normal SCSI Protocol. Thus there are no Phases, no Messages, no sharable bus, (only one
Host Computer) and no SCSI Hardware. For those who are familiar with the current SCSI-3 effort, this Standard will not
conform with that Packetized Standard.

4.5.1 Differences from the SCSI Standard
Some of the major differences from the SCSI Standard:
•

Status will use the ATAPI description, rather than a Data Byte passed at the end of the command.

•

ATAPI Device is slave during operation rather than the master view of a SCSI Peripheral.

•

No messages are supported.

•

No disconnect/reconnect or any of the SCSI Pointers.

•

No linking.

•

No queueing of commands.

•

All CD-ROM Command Packets (CP) are 12 bytes in length, rather than the 6, 8, 10 or 12-byte
packets of the SCSI Standard; however, 16-byte ATAPI Command Packets are defined for SAM
compatibility for future Devices. The size of the Command Packet required by a Device is defined
in word 0 of the ATAPI Identify Device command, allowing Host System Device Drivers to determine the size of the Command Packets before issuing an ATAPI Command Packet.

•

No allegiance conditions are used.

This standard will make use of many of the Standard SCSI Command Block definitions and Commands, but some of the
commands that would normally be supported by a SCSI Device will not be supported for various reasons. These com-

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ATAPI Overview
How SCSI is Used by ATAPI

mands are:
•

Reserve and release; as there is only one Host allowed, this is not needed.

•

Send and receive diagnostics; the ATA EXECUTE DRIVE DIAGS command replaces these
commands.

•

Change definitions; as there is no SCSI, this command is nonsensical.

•

Copy / Copy and Verify; no shared bus so this command can’t be implemented.

•

Compare; no shared bus, so this command can’t be implemented.

•

Read and Write Buffer; simplification.

•

Log Sense and Select; simplification.

•

Search Data; simplification.

•

Verify; simplification.

4.5.2 Redundant Command Functionality (Task File vs. Packet)
The SCSI Standard has provided some commands that the ATA Standard also provides. It is the intent of this standard to
allow all the functionality to exist, by utilizing only Command Packets. This will allow existing SCSI like drivers to continue to issue packets for all operation, and have some lower level driver convert them to the ATAPI protocol. Unfortunately there are existing low level drivers that would like to continue to use some non data transfer ATA Task File
commands. As such both these “Task File” and “Packet” commands will be supported.

4.5.2.1 Door Lock and Door Unlock vs. Prevent / Allow Medium Removal
There is a need to support a removable Device protocol that allows the Device to send a request to the Host to unlock
and/ or Eject the media. There is already an existing methodology that provides this capability in ATA. The devicerequested eject is performed by setting the MCR bit in the Error Register and issuing an Error status to the Host (ERR
bit in the Status Register) for all subsequent DOOR LOCK commands. The Host would then issue an ACKNOWLEDGE MEDIA CHANGE command to indicate that it will perform the Unlock / Eject sequence. The SCSI PREVENT/
ALLOW MEDIUM REMOVAL command only allows the host to “Prevent” the user from removing the media and not
to signal when the user needs to remove the media. As such both the ATA and Packet (ATAPI) versions of the commands will be supported. When the ATA Door Lock is used, only the MCR bit will be presented to the host, which can
then poll for this condition. When the Packet commands are used the MCR / Door Lock sequence will not be used. The
Door Lock / Unlock command is optional, but if the MCR bit is set by the device, it shall be supported.

4.5.2.2 ATAPI Identify Drive vs. Inquiry
The ATAPI IDENTIFY DRIVE command has information that the low level drivers use to perform ATA interface hardware configuration. Information in the Identify Drive shall continue to look exactly as the ATA Identify Drive does for
compatibility reasons. As the information in the Inquiry Command cannot be returned by the ATAPI Identify Drive
Command, the Inquiry Command will be supported for use by higher level drivers.

4.5.2.3 Initialize Drive Parameters and Set Features vs. Mode Sense and Mode Select
The INITIALIZE DRIVE PARAMETERS command does not contain a method to provide non ATA device configuration information, and will not be used. As such the Mode Select and Mode Sense from the SCSI standard shall be supported. The combination of Mode Select and Set Features commands contain all the necessary functionality and is most
compatible with the existing BIOSes and OS Drivers.

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ATAPI CD-ROM Specification
ATAPI Protocol

5.0 ATAPI Protocol
The ATAPI Device is commanded by two methods, the original ATA Commands utilizing the Task File and the new
Packet Command method. For both methods, the devices using this interface shall be programmed by the host computer
to perform commands and return status to the host at command completion. When more than one Device is daisy chained
on the interface, commands are written in parallel to all peripherals, and for ATA commands except the Execute Diagnostics command, only the selected Device (DRV bit in the Drive/Head ATA Register) executes the command. On an
Execute Diagnostics command addressed to Device 0, both devices shall execute the command, and Device 1 shall post
its status to Device 0 via PDIAG-.
The “Protocol” for ATAPI centers around the usage of a new ATA Command called “ATAPI Packet Command.” All
the normal ATA rules and protocol are used to issue the Packet Command, but once the command has been issued, a new
set of rules applies:
1.

The interpretation of the DRQ bit in the Status Register shall be used along with the Interrupt Reason Registers
to determine the actual Interrupt Type.

2.

The actual command for the Device to execute is sent as a packet via the data register, and not the Task File.

3.

Command arguments are supplied by the Command Packet as well as from the Task File.

4.

A Byte Count is used to determine the amount of data the Host shall transfer at each DRQ Interrupt.

5.

The ATAPI Features Register is used to indicate when DMA will be used rather than by using different opcodes.

6.

The final status is presented to the Host as a new interrupt after the last data has been transferred, rather than along
with the last block of data.

These new rules (protocol) only apply from after the issuance of the Packet Command, until the Completion Status has
been read by the Host. After the Completion Status has been read, the Task File Register definitions and Protocol revert
to the standard ATA definition.

5.1 Initialization
The ATAPI Device will respond just as defined in the ATA Standard. The DASP and PDIAG signals will only be utilized following a POR or hardware reset condition. Although the ATA SRST is not used for initialization by ATAPI devices, the “Software reset” defined in the ATA Standard shall be utilized.

5.2 ATAPI PACKET Command
The ATAPI Packet Command is issued exactly as normal ATA commands, by initializing the Task File Registers, setting
the Drive Selection Bit and writing the Command byte into the Command Register. With normal ATA commands a
DRQ (Optional Interrupt) would be generated to indicate that the data for the command could be transferred to/from the
Device. With the Packet Command, the first DRQ indicates that the Command Packet Data shall be written to the Device. Once the Command Packet has been sent, the command proceeds as a normal ATA command would. The Command Packet bytes shall always be transferred via PIO and never using DMA.
ATA Packet Commands can be issued regardless of the state of the DRDY Status Bit.
If while polling BSY the device remains in a state where it cannot accept a command for more than 5 seconds, the Host
shall time out and reset the device.
Data transfers may be accomplished in more ways than are described by this standard, but the sequences described in this
Standard shall be used to remain compatible with current and future ATAPI Devices.

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ATAPI Protocol
Status Register Utilization for Packet Commands

5.3 Status Register Utilization for Packet Commands
See "6.7 ATAPI Register Map (Packet Command)" on page 54 for a description of the register definition.

5.4 Byte Count Register (Cylinder Low/High) Usage for Packet Commands
This register is used to control the number of bytes the Host shall transfer at each DRQ. It is only used for the command
parameter data being transferred via PIO and never for DMA or Command Packet bytes.
Since the length of data that is actually transferred to and from an ATAPI Device using PIO is controlled by the Host,
and since the ATAPI Device needs to be able to control the number of bytes transferred, an additional capability was
needed. By using the Byte Count Register, a capability to transfer a variable number of bytes has been created. In ATAPI the Device indicates to the Host the number of bytes that shall be transferred on each DRQ Interrupt. Before transferring data, the Host shall read the 16-bit Byte Count Register, and comply with the length requested. Both the ATAPI
Device and the Host will have their own byte counts and will transfer until those counts go to zero. For some commands,
such as Mode Sense, the Host does not know the amount of data that will be transferred, and shall rely on the Byte Count
supplied by the Device to transfer the correct amount of data.
A further capability of the Byte Count Register is for the Host to signal to the ATAPI Device the maximum amount of
data it can take in a single PIO DRQ packet and or the preferred packet size. For all commands that require data be transferred, the Host shall set the Byte Count Register to the desired length before issuing the Packet Command. This length
shall be used by the ATAPI Device as the maximum size for each PIO or DMA data packet. The Device can choose to
transfer packets smaller than those set by the host in the Byte Count Register.
The Host has the capability to limit the number of bytes transferred on each DRQ. This limit is communicated to the Device in the Byte Count Register when the Packet Command is issued. The Release is intended to be used only on Block
Boundaries and since this DRQ limit could then cause a Release in the middle of a block (if the limit is set smaller than
the amount of data to be transferred for one sector), the minimum size of the DRQ limit shall be no smaller than the
length of data to be transferred for one sector from the media. This limitation would only be valid for Media Access commands and not applicable to Mode Sense, Inquiry, etc. If the byte count is odd and the amount of data to be sent is larger
than the limit, then the amount of data sent on each DRQ shall be less than the specified value as a drive shall not send
odd length DRQs, except for the last transfer. Given this, the odd byte count transfer limit in the BC registers cannot be
used. The device shall always round down the value to the next lower even number, unless the transfer length matches
the actual total transfer length exactly.
When a Read command is being processed, the ATAPI Device may wish to send all the data that is available in its buffers on just one DRQ Interrupt, with the limitation that only 65534 bytes may be transferred at one time.

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ATAPI CD-ROM Specification
ATAPI Protocol

Table 3 - Byte Count Register Usage
Operation
Send Command Packet

Parameters to the Packet Command (Task File Contents)

Parameter Data from the Device
to the Host (e.g. data from a Read,
or Inquiry command)
Parameter Data from the Host to
the Device (e.g. data for a Write,
or Mode Select command)

Usage (PIO)
Is used as a parameter to the Packet Command and is not used to control the Packet
transfer.
As a parameter to any Packet Command that
will transfer parameter data, the Byte Count
is used by the Host to communicate the maximum / preferred amount of data to be transferred on each DRQ.
At each DRQ / DMARQ the count contains
the number of bytes that the Host shall transfer from the Device.
At each DRQ / DMARQ the count contains
the number of bytes that the Host shall transfer to the Device.

Usage (Non-Overlapped DMA)
Command Packet is always sent via Programmed I/O and not DMA.
The Device can ignore the byte count, as the
actual transfers are controlled via the ATAPI
Device and not the Host.

The ATAPI Device can transfer data whenever it wishes, and as such the Byte Count
shall not be used.
The ATAPI Device can transfer data whenever it wishes, and as such the Byte Count
shall not be used.

If the Device requests more data be transferred than required by the command protocol, the Host shall pad when sending
data to the Device, and dump extra data into a bit bucket when reading data from the Device.
On odd byte transfers, the only permissible time for an actual Odd Byte Count value will be on the Last DRQ, intermediate DRQs shall contain even byte counts.
The peripheral is not responsible for padding the data. Only the specific amount of data specified by the host byte count
shall be transferred. Transfers exceeding the host byte count may cause data corruption.

5.5 Sector Count (ATAPI Interrupt Reason) Register Usage for Packet Commands
The Interrupt Reason Register contains an expanded definition of the ATA DRQ Status. When the DRQ is presented in
the ATAPI Status Register for an ATAPI Packet Command, the contents of this register indicate if Packet Command or
User Data shall be transferred and, if so, the direction of the transfer, as well as Release and Completion State information.

5.6 Immediate Command Operation
Some of the ATAPI Commands are immediate. These commands return Completion Status immediately, with the actual
execution of the command continuing. When the actual completion of the seek operation of immediate commands has
occurred, the Device shall set the DSC bit in the Status Register.
•

ATA commands operate differently from packet commands. When a new ATA command is written to the Command
Register, before a command has completed, the executing command stops execution and the new command is aborted
with an Aborted Command error.

•

If after reporting completion of an Immediate Mode command (Seek, Play Audio, etc.) the device receives a new command before actual completion of the execution of the prior command, the device shall accept the new command and
execute it when able.

•

New ATAPI packet commands received while a previous packet command is still executing shall cause both commands to be aborted with an error, “Check Condition”.

•

If an Immediate Mode command is executing when the devices is issued an SRST the DSC bit shall not be cleared
with the rest of the status register. Instead the functionality of the DSC bit shall be maintained.

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ATAPI Protocol
Overlapped Operation

5.7 Overlapped Operation
Devices reporting support for Overlapped commands are capable of improving system performance by releasing the
ATA bus to another device before completing a command in progress. For more detail see "5.17 Overlapped Command
Operation" on page 39.

5.7.1 Example of ATAPI Overlap with only one ATAPI Peripheral

Status

Data

[Process Overlapped Command]

DRV Bit
INTRQ

Data

Status

Command

Data

Status

AT
A

D

riv
e

Command

O

ve
r

la

p

Ca

pa

bl

eD

riv
e

•

Release

•
•

Service

ATAPI Drive Releases the Task File Ownership after acceptance of an ATAPI command.
Overlap Mode is enabled on each command via the ATAPI Features Register.
Overlapped Commands are issued to an ATA (Legacy) Drive while an ATAPI Command is still processing.
Interrupts are generated from the selected device only. Thus the Driver must always select the Overlap capable device
when there is no active command to a Legacy Device.
Device uses Interrupt & SERVICE Status to gain Host’s attention. SERVICE Status set when any service is needed.
Driver uses the A2h (Service) Command to give control of the Task File Registers back to the Device after an Interrupt
and Sensing the SERVICE status bit.
The Interrupt Reason RELEASE Status bit is used to indicate a Release Interrupt.

Command

•
•
•
•

Optional
Interrupt

Optional
Interrupt

BSY
DRQ

Figure 1 - Example ATAPI Overlap Command Sequence

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ATAPI Protocol
5.8 Flow of Packet Command, PIO Data In to Host
This class includes commands such as Inquiry, Read etc. Execution includes the transfer of some unknown number of
data bytes from the Device to the host.
1.

The host Polls for BSY=0, DRQ=0 then initializes the task file by writing the required parameters to the Features,
Byte Count, and Drive/Head registers.

2.

The host writes the Packet Command code (A0h) to the Command Register.

3.

The Device sets BSY, before the next system read of the status register, and prepares for Command Packet transfer.

4.

When the Device is ready to accept the Command Packet, the Device sets CoD and clears IO. DRQ shall then be
asserted simultaneous or prior to the de-assertion of BSY. Some Devices will assert INTRQ following the assertion of DRQ. See section 7.1.7.1, "General Configuration Word (0)", on page 63 for command packet DRQ types
and other related timing information.

5.

After detecting DRQ, the host writes the 12 bytes (6 words) of Command to the Data Register.

6.

The Device(1) clears DRQ (when the 12th byte is written), (2) sets BSY, (3) reads Features and Byte Count requested by the host system, (4) prepares for data transfer.

7.

When data is available, the Device:(1) places the byte count of the data available into the Cylinder High and Low
Registers, (2) sets IO and clears CoD, (3) sets DRQ and clears BSY, (4) sets INTRQ.

8.

After detecting INTRQ, the host reads the DRQ bit in the Status Register to determine how it shall proceed with
the command. If DRQ= 0 then the device has terminated the command. If DRQ=1 then the host shall read the data
(number of bytes specified in the Cylinder High/Low Registers) via the Data Register. In response to the Status
Register being read, the Device negates INTRQ for both cases.

9.

The Device clears DRQ. If transfer of more data is required, the Device also sets BSY and the above sequence is
repeated from step 7.

10. When the Device is ready to present the status, the Device places the completion status into the Status Register,
sets CoD, IO, DRDY and, prior to asserting INTRQ, clears BSY and DRQ.
11. After detecting INTRQ & DRQ=0 the host reads the Status Register and if necessary, the Error Register for the
command completion status.
The DRQ signal is used by the device to indicate when it is ready to transfer data, and is cleared during the last byte of
data to be transferred. This applies for both Command Packet as well as normal read/write data.

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Host Computer

ATAPI Protocol
Flow of Packet Command, PIO Data In to Host

ATAPI Device

Clears BSY,
Wait for BSY=0, DRQ=0
Initialize Task File
Issue Packet Command
Sets BSY
.
.
.
Ready for Command Packet
Set CoD, clear BSY, IO
Assert DRQ/ INTRQ
Wait for DRQ or INTRQ
Write Command Packet Bytes

Negate DRQ after 12th (or 16th) byte
Set BSY
Perform command
.
.
Set Byte Count in Cylinder High/Low
Set DRQ, IO clear BSY, CoD
Assert INTRQ

Wait for INTRQ
Read Status
If DRQ = 1
Read Cylinder High/Low (Byte Count)
Transfer Data Bytes

Negate INTRQ

Loop if more
data to transfer
Set BSY

Set status in Status Register
Set IO, CoD, DRDY; Clear DRQ, BSY

If DRQ = 0 (Command terminated)
Read Status

Assert INTRQ

Negate INTRQ

If Error, Read Error Register

Solid Lines indicate control flow, and dotted lines are actions taken but without direct control flow change occurring.
This Diagram is for Visualization only, design to text.

Figure 2 - Packet Command with PIO Data In to Host

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ATAPI Protocol
5.9 Flow of Overlapped Commands with Data Transfer In to Host
This class includes commands such as Inquiry, Read etc. Execution includes the transfer of some unknown number of
data bytes from the Device to the host.
1.

The host Polls for BSY=0, DRQ=0 then initializes the task file by writing the required parameters to the Features,
Byte Count, and Drive/Head registers. The OVERLAP bit in the ATAPI FEATURES Register must be set (1).

2.

The host writes the Packet Command code (A0h) to the Command Register.

3.

The Device sets BSY, before the next system read of the status register, and prepares for Command Packet transfer.

4.

When the Device is ready to accept the Command Packet, the Device sets CoD and clears RELEASE, IO. DRQ
shall then be asserted simultaneous or prior to the de-assertion of BSY. Some Devices will assert INTRQ following the assertion of DRQ. See section 7.1.7.1, "General Configuration Word (0)", on page 63 for command packet
DRQ types and other related timing information.

5.

After detecting DRQ, the host writes the 12 bytes (6 words) of Command to the Data Register.

6.

The Device(1) clears DRQ (when the 6th word is written), (2) sets BSY, (3) reads Features and Byte Count requested by the host system, (4) prepares for either Release of the ATA Bus or Data Transfer.

7.

If the Device has NOT been previously commanded to generate an interrupt after accepting the Packet Command
Data, the Device may optionally not release the ATA Bus. In this case the device shall move directly from accepting the Command Packet Data to Data Transfer (Step 12. below) with DRQ=1, CoD=0 and IO = 0. This must also
be done within the time reported the Identify Drive Data Command Data. See "7.1.7.16 Typical Time for the Release After Command Received (Word 71)" on page 67. If the Device has been commanded to generate an interrupt after processing the Packet Command, the Device shall always release the ATA Bus.

8.

The Device (1) sets the RELEASE bit in the ATAPI STATUS Register, (2) clears IO, CoD, DRQ, (3) clears BSY.
If the Device has been previously commanded to generate an interrupt when releasing the ATA Bus after receiving a Packet Command, the Device shall set INTRQ (1).

9.

Released State.
---- At this point the Host is free to select the other Device and Issue Commands ----- When the Host is Not using the Non Overlapped Device it selects the Overlap Device allowing it to interrupt ---

10. When the Device is ready to accept data, the Device (1) sets the SERVICE Bit in the ATAPI STATUS Register,
(2) sets DRQ, (3) sets INTRQ.
11. After detecting INTRQ, the Host shall read the ATAPI STATUS Register to determine if the selected device is
requesting service. If there is an overlapped command active on the non-selected device, the Host shall change
the DRV Bit and read the ATAPI STATUS Register to determine if service is also needed on the non-selected Device. When the state of both Device’s SERVICE bits are known the Host shall select one of the Devices, that is
requesting service, and issue the Service (A2h) Command. The Host shall employ some fairness technique in
choosing which Device will be serviced.

12. When the Device receives the Service Command or if moving directly from Packet Command Data to Data Transfer or from Back-to-Back Data Transfers, the Device (1) places the byte count of the data available into the Cylinder High and Low Registers, (2) clears SERVICE, (3) sets IO and clears CoD, (4) sets DRQ and clears BSY. If

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ATAPI Protocol
Flow of Overlapped Commands with Data Transfer In to Host

the Device has been previously commanded to generate an interrupt when done processing the Service Command,
the Device shall set INTRQ (1).
13. After detecting INTRQ or that BSY has been cleared, the host reads the DRQ bit in the Status Register to determine how it will proceed with the command. If DRQ= 0 then the device has either released the ATA Bus or terminated the command. If DRQ=1 then the host shall read the data (number of bytes specified in the Cylinder
High/Low Registers) via the Data Register. In response to the Status Register being read, the Device negates INTRQ for both cases.
14. If no more data is to be transferred, proceed to step 19.
15. One of two possibilities exists, either Release or back-to-back data transfers. If Release, proceed to Step 17.
16. The device (1) sets Busy; (2) clears DRQ; and (3) the Release bit is cleared. The IO CoD bits remain the same.
Proceed to step 12.
17. The Device (1) leaves BSY cleared, (2) clears DRQ. The RELEASE Bit shall have been set at the beginning of
the last data transfer. The IO and CoD bits shall remain in the same state as for a normal data transfer, this distinguishes the “Release” from a “Status” state.
18. The above sequence is repeated from step 9.
19. The Device clears DRQ and sets BSY.
20. The Device places the completion status into the Status Register, sets CoD, IO, DRDY, clears RELEASE, BSY,
and DRQ, prior to asserting INTRQ.
21. After detecting INTRQ & DRQ=0, the host reads the Status Register and if necessary, the Error Register for the
command completion status. If the Host detects that the RELEASE Bit or that both IO and CoD are not set this is
not a status state but a release state and should proceed accordingly.
The DRQ signal is used by the device to indicate when it is ready to transfer data, and is cleared after (during) the last
byte of data to be transferred. This applies for both Command Packet as well as normal read/write data.
The RELEASE Bit is used to signal that the Drive has released the ATA Bus. The RELEASE Bit shall be qualified by
the host with both BSY and DRQ cleared. If either BSY or DRQ is set, then the value in the RELEASE bit is undefined.

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ATAPI CD-ROM Specification
ATAPI Protocol

Host Computer
Wait for BSY=0, DRQ=0
Initialize Task File
Issue Packet Command

ATAPI Device
Clears BSY,
Sets BSY
.
.
.
Ready for Command Packet
Set CoD, clear BSY, IO
Assert DRQ/ INTRQ

Wait for DRQ or INTRQ
Write Command Packet Bytes

Negate DRQ after 12th (or 16th) byte
Set BSY

Wait for INTRQ or BSY Release

Decode and Check Command
Set RELEASE, Clear IO & CoD
Clear BSY and Optionally set INTRQ
Perform command

Issuing of Commands to Other Device Possible Here
When done, reselect the overlap Device

Wait for INTRQ
Read Status
If SERVICE set, Issue Service (A2h) Command

Wait for INTRQ or BSY being cleared
Read Status
If DRQ = 0 & RELEASE or if Cod & IO are not set
If DRQ = 1
Read Cylinder High/Low (Byte Count)
Transfer Data Bytes
If DRQ = 0 and Cod & IO are set (Completion)

Clear DRQ & BSY
When Ready to transfer data
Set SERVICE and Assert INTRQ
Negate INTRQ
Set BSY
Set Byte Count in Cylinder High/Low
Set DRQ, IO clear BSY, CoD, SERVICE
Optionally Assert INTRQ
If Release after xfer, set RELEASE
Negate INTRQ
Loop if release &
Loop if Back to Back
more data to transfer

Set BSY.
Set status in Status Register
Set IO, CoD, DRDY; Clear DRQ, BSY
Assert INTRQ

Read Status
Negate INTRQ
If Error, Read Error Register

Solid Lines indicate control flow, and dotted lines are actions taken but without direct control flow change occurring.
This Diagram is for Visualization only, design to text.

Figure 3 - Overlapped Packet Command with PIO Data In to Host
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ATAPI Protocol
Flow of Packet Command with PIO Data Out from the Host

5.10 Flow of Packet Command with PIO Data Out from the Host
This class includes commands such as Mode Select, Write etc. Execution includes the transfer of some known number
of data bytes from the Host to the Device.
1.

The host Polls for BSY=0, DRQ=0 then initializes the task file by writing the required parameters to the Features,
Byte Count, and Drive/Head registers.

2.

The host writes the Packet Command code (A0h) to the Command Register.

3.

The Device sets BSY, before the next system read of the status register, and prepares for Command Packet transfer.

4.

When the Device is ready to accept the Command Packet, the Device sets CoD and clears IO. DRQ shall then be
asserted simultaneous or prior to the de-assertion of BSY. Some Devices will assert INTRQ following the assertion of DRQ. See section 7.1.7.1, "General Configuration Word (0)", on page 63 for command packet DRQ types
and other related timing information.

5.

After detecting DRQ, the host writes the 12 bytes (6 words) of Command to the Data Register.

6.

The Device(1) clears DRQ (when the 12th byte is written), (2) sets BSY, (3) reads Features and Byte Count requested by the host system, (4) prepares for data transfer.

7.

When ready to transfer data, the Device:(1) sets the byte count (Cylinder High and Low Registers) to the amount
of data that the Device wishes to be sent, (2) clears IO and CoD, (3) sets DRQ and clears BSY, (4) sets INTRQ.
The Byte Count would normally be set to the number of bytes requested by the contents of the register at the receipt of the command, but may be any amount that the Device can accommodate in its buffers at this time.

8.

After detecting INTRQ, the host reads the DRQ bit in the Status Register to determine how it shall proceed with
the command. If DRQ= 0 then the device has terminated the command. If DRQ=1 then the host shall write the
data (number of bytes specified in the Cylinder High/Low Registers) via the Data Register. In response to the Status Register being read, the Device negates INTRQ for both cases.

9.

The Device clears DRQ and sets BSY. If transfer of more data is required, the above sequence is repeated from 7.

10. When the Device is ready to present the status, the Device places the completion status into the Status Register,
sets CoD, IO, DRDY and clears BSY, DRQ, prior to asserting INTRQ.
11. After detecting INTRQ & DRQ=0 the host reads the Status Register and if necessary, the Error Register for the
command completion status.
The DRQ signal is used by the device to indicate when it is ready to transfer data, and is cleared after (during) the last
byte of data to be transferred. This applies for both Command Packet as well as normal read/write data.

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ATAPI Protocol

Host Computer

ATAPI Device

Clears BSY
Wait for BSY=0, DRQ=0
Initialize Task File
Issue Packet Command
Sets BSY
.
.
.
Ready for Command Packet
Set CoD, clear BSY, IO
Assert DRQ/ INTRQ
Wait for DRQ or INTRQ
Write Command Packet Bytes

Negate DRQ after 12th (or 16th) byte
Set BSY
Perform command
.
.
Set Byte Count in Cylinder High/Low
Set DRQ, clear BSY, CoD, IO
Assert INTRQ

Wait for INTRQ
Read IRQ Status
If DRQ = 1
Read Cylinder High/Low (Byte Count)
Transfer Data Bytes

Negate INTRQ

Loop if more
data to transfer
Set BSY

Set status in Status Register
Set IO, CoD, DRDY; Clear DRQ, BSY

If DRQ = 0 (Command terminated)
Read Status

Assert INTRQ

Negate INTRQ

If Error, Read Error Register

Solid Lines indicate control flow, and dotted lines are actions taken but without direct control flow change occurring.
This Diagram is for Visualization only, design to text.

Figure 4 - Packet Command with PIO Data Out from Host

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ATAPI Protocol
Flow of Overlapped Commands with Data Transfer Out From Host

5.11 Flow of Overlapped Commands with Data Transfer Out From Host
This class includes commands such as Mode Select, Write etc. Execution includes the transfer of some unknown number
of data bytes from the Host to the Device.
1.

The host Polls for BSY=0, DRQ=0 then initializes the task file by writing the required parameters to the Features,
Byte Count, and Drive/Head registers. The OVERLAP bit in the ATAPI FEATURES Register must be set (1).

2.

The host writes the Packet Command code (A0h) to the Command Register.

3.

The Device sets BSY, before the next system read of the status register, and prepares for Command Packet transfer.

4.

When the Device is ready to accept the Command Packet, the Device sets CoD and clears RELEASE, IO. DRQ
shall then be asserted simultaneous or prior to the de-assertion of BSY. Some Devices will assert INTRQ following the assertion of DRQ. See section 7.1.7.1, "General Configuration Word (0)", on page 63 for command packet
DRQ types and other related timing information.

5.

After detecting DRQ, the host writes the 12 bytes (6 words) of Command to the Data Register.

6.

The Device(1) clears DRQ (when the 6th word is written), (2) sets BSY, (3) reads Features and Byte Count requested by the host system, (4) prepares for either Release of the ATA Bus or Data Transfer.

7.

If the Device has NOT been previously commanded to generate an interrupt after accepting the Packet Command
Data, the Device may optionally not release the ATA Bus. In this case the device must move directly from accepting the Command Packet Data to Data Transfer (Step 12. below) with DRQ=1, CoD=0 and IO = 0. This must also
be done within the time reported the Identify Drive Data Command Data. See "7.1.7.16 Typical Time for the Release After Command Received (Word 71)" on page 67. If the Device has been commanded to generate an interrupt after processing the Packet Command, the Device shall always release the ATA Bus.

8.

The Device (1) sets the RELEASE bit in the ATAPI STATUS Register, (2) clears IO, CoD, DRQ, (3) clears BSY.
If the Device has been previously commanded to generate an interrupt when releasing the ATA Bus after receiving a Packet Command, the Device shall set INTRQ (1).

9.

Released State.
---- At this point the Host is free to select the other Device and Issue Commands ----- When the Host is Not using the Non Overlapped Device it selects the Overlap Device allowing it to interrupt ---

10. When the Device is ready to accept data, the Device (1) sets the SERVICE Bit in the ATAPI STATUS Register,
(2) sets DRQ, (3) sets INTRQ.
11. After detecting INTRQ, the Host shall read the ATAPI STATUS Register to determine if the selected device is
requesting service. If there is an overlapped command active on the non-selected device, the Host shall change
the DRV Bit and read the ATAPI STATUS Register to determine if service is also needed on the non-selected Device. When the state of both Device’s SERVICE bits are known the Host shall select one of the Devices, that is
requesting service, and issue the Service (A2h) Command. The Host shall employ some fairness technique in
choosing which Device will be serviced.

12. When the Device receives the SERVICE Command or if moving directly from Packet Command Data to Data
Transfer or from Back-to-Back Data Transfers, the Device (1) places the byte count of the data available into the
Cylinder High and Low Registers, (2) clears SERVICE, (3) clears IO and CoD, (4) sets DRQ and clears BSY. If

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ATAPI Protocol
the Device has been previously commanded to generate an interrupt when done processing the SERVICE Command, the Device shall set INTRQ (1).
13. After detecting INTRQ or that BSY has been cleared, the host reads the DRQ bit in the Status Register to determine how it will proceed with the command. If DRQ= 0 then the device has either released the ATA Bus or terminated the command. If DRQ=1 then the host shall write the data (number of bytes specified in the Cylinder
High/Low Registers) via the Data Register. In response to the Status Register being read, the Device negates INTRQ for both cases.
14. If no more data is to be transferred, proceed to step 19.
15. One of two possibilities exists, either Release or back-to-back data transfers. If Release, proceed to Step 17.
16. The device (1) sets Busy; (2) clears DRQ; and (3) the Release bit is cleared. The IO CoD bits remain the same.
Proceed to step 12.
17. The Device (1) leaves BSY cleared, (2) clears DRQ. The RELEASE Bit shall have been set at the beginning of
the last data transfer. The IO and CoD bits shall remain in the same state as for a normal data transfer, this distinguishes the “Release” from a “Status” state.
18. The above sequence is repeated from step 9.
19. The Device clears DRQ and sets BSY.
20. The Device places the completion status into the Status Register, sets CoD, IO, DRDY, clears RELEASE, BSY,
and DRQ, prior to asserting INTRQ.
21. After detecting INTRQ & DRQ=0, the host reads the Status Register and if necessary, the Error Register for the
command completion status. If the Host detects that the RELEASE Bit or that both IO and CoD are not set this is
not a status state but a release state and should proceed accordingly.

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ATAPI Protocol
Flow of Overlapped Commands with Data Transfer Out From Host

Host Computer
Wait for BSY=0, DRQ=0
Initialize Task File
Issue Packet Command

ATAPI Device
Clears BSY,
Sets BSY
.
.
.
Ready for Command Packet
Set CoD, clear BSY, IO
Assert DRQ/ INTRQ

Wait for DRQ or INTRQ
Write Command Packet Bytes

Negate DRQ after 12th (or 16th) byte
Set BSY

Wait for INTRQ or BSY Release

Decode and Check Command
Set RELEASE, Clear IO & CoD
Clear BSY and Optionally set INTRQ
Perform command

Issuing of Commands to Other Device Possible Here
When done, reselect the overlap Device

Wait for INTRQ
Read Status
If SERVICE set, Issue Service (A2h) Command

Wait for INTRQ or BSY being cleared
Read Status
If DRQ = 0 & RELEASE or if Cod & IO are not set
If DRQ = 1
Read Cylinder High/Low (Byte Count)
Transfer Data Bytes
If DRQ = 0 and Cod & IO are set (Completion)

Clear DRQ & BSY
When Ready to accept data
Set SERVICE and Assert INTRQ
Negate INTRQ
Set BSY
Set Byte Count in Cylinder High/Low
Set DRQ, clear IO, BSY, CoD, SERVICE
Optionally Assert INTRQ
If Release after xfer, set RELEASE
Negate INTRQ
Loop if release &
Loop if Back to Back
more data to transfer

Set BSY.
Set status in Status Register
Set IO, CoD, DRDY; Clear DRQ, BSY
Assert INTRQ

Read Status
Negate INTRQ
If Error, Read Error Register

Solid Lines indicate control flow, and dotted lines are actions taken but without direct control flow change occurring.
This Diagram is for Visualization only, design to text.

Figure 5 - Overlapped Packet Command with PIO Data Out From Host
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5.12 Flow of Non-Overlap DMA Data Commands
This class includes commands such as Read, Write etc. Execution includes the transfer of some unknown number of
data bytes.
1.

The host Polls for BSY=0, DRQ=0 then initializes the task file by writing the required parameters to the Features,
Byte Count, and Drive/Head registers. The host must also initializes the DMA engine which will service the Devices requests.

2.

The host writes the Packet Command code (A0h) to the Command Register.

3.

The Device sets BSY and prepares for Command Packet transfer.

4.

When the Device is ready to accept the Command Packet, the Device sets CoD and clears IO. DRQ shall then be
asserted simultaneous or prior to the de-assertion of BSY. Some Devices will assert INTRQ following the assertion of DRQ. See section 7.1.7.1, "General Configuration Word (0)", on page 63 for command packet DRQ types
and other related timing information.

5.

After detecting DRQ, the host writes the 12 bytes (6 words) of Command to the Data Register.

6.

The Device(1) clears DRQ (when the 12th byte is written), (2) sets BSY, (3) reads Features and Byte Count requested by the host system, (4) prepares for data transfer.

7.

When ready to transfer data, the Device transfers via DMARQ/DMACK any amount that the Device can accommodate or has in its buffers at this time. This continues until all the data has been transferred.

8.

When the Device is ready to present the status, the Device places the completion status into the Status Register,
and sets IO, CoD, DRDY and clears BSY, DRQ, prior to asserting INTRQ.

After detecting INTRQ the host reads the Status Register for the command completion status.

5.13 Flow of Non-data Commands
This class includes commands such as Seek, etc. Execution of these commands involves no data transfer.
1.

The host Polls for BSY=0, DRQ=0 then initializes the task file by writing the required parameters to the Features,
Byte Count, and Drive/Head registers.

2.

The host writes the Packet Command code (A0h) to the Command Register.

3.

The Device sets BSY and prepares for Command Packet transfer.

4.

When the Device is ready to accept the Command Packet, the Device sets CoD and clears IO. DRQ shall then be
asserted simultaneous or prior to the de-assertion of BSY. Some Devices will assert INTRQ following the assertion of DRQ. See section 7.1.7.1, "General Configuration Word (0)", on page 63 for command packet DRQ types
and other related timing information.

5.

After detecting DRQ, the host writes the 12 bytes (6 words) of Command to the Data Register.

6.

The Device sets BSY and executes the command.

7.

When the Device is ready to present the status, the Device places the completion status into the Status Register,
and sets IO, CoD, DRDY and clears BSY, DRQ, prior to asserting INTRQ.

8.

After detecting INTRQ, the host reads the Status Resister for the command completion status.

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ATAPI Protocol
Timing of Non-Overlap Packet Command

5.14 Timing of Non-Overlap Packet Command

Write CMD
Read Status
Rd/Wr Data
Less than 50µs
or 3MS if using Interrupt

BSY
I/O
CoD
Byte Count
5µs Maximum

DRQ
Optional use
of Interrupt

INTRQ

Figure 6 - Timing of Command Packet Transfer

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ATAPI Protocol
5.15 Timing of Non-Overlap Data and Status Transfer

Read Status
Rd/Wr Data
Data Transfer

Completion Status

BSY
I/O
CoD
Byte Count
5µs Maximum

DRQ
INTRQ
Flow

Figure 7 - Timing of Data and Status Transfer

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ATAPI Protocol
Control Signal Timing Requirements and Relationships

5.16 Control Signal Timing Requirements and Relationships
The order that the signals change shall adhere to the following conditions:
1.

Upon receiving the A0h ATAPI Packet Command the Device shall have BSY asserted until the next host access
of the Status Register where the device can guarantee that CoD=1 and IO=0.

2.

The Device shall not assert DRQ until CoD and IO are valid for the command or data packet to be transferred and
the device is ready to perform that transfer.

3.

The Device shall clear BSY and set DRQ within the time-out specified by the CMD DRQ Type. See section
7.1.7.1, "General Configuration Word (0)", on page 63 for additional information.

4.

Devices reporting CMD DRQ Type “Accelerated” shall de-assert DRQ within 5us of the last word transferred for
a command or data packet unless Back-to-Back Data Transfers in an overlapped mode are performed.

5.

Devices reporting a CMD DRQ Type other than “Accelerated” shall de-assert DRQ, before asserting INTRQ, following the last word transferred for a command or data packet.

Implementer’s Note: Early ATAPI Devices reporting CMD DRQ Types other than “Accelerated” may not be able to deassert DRQ before the next INTRQ. Host systems should therefore wait until the device asserts INTRQ before testing
DRQ following the transfer of the last data word in a command or data packet.

See section 7.1.7.1, "General Configuration Word (0)", on page 63 for additional DRQ and other timing related information.

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ATAPI Protocol
5.17 Overlapped Command Operation
Devices reporting support for Overlapped commands are capable of improving system performance by releasing the
ATA bus to another device before completing a command in progress. The host system can enable this feature by setting
the OVERLAP bit in the Feature Register when it issues an ATAPI Packet command. The device uses the RELEASE bit
in the ATAPI Interrupt Reason register to notify the host that it has released the ATA bus before it has completed the
command in progress.
•

Releasing the ATA bus to another device is at the discretion of the device processing an Overlapped command. Devices should only Release the ATA Bus, before a command has completed, when the host will not need to service an
Interrupt or DRQ from the device for more than the time specified in words 71 and 72 of the devices identify drive
data. This is typically the cases for seeks on mechanically slower devices such as CD-ROM and Tape.

•

When the host detects a “Release” from a device to which it has sent an overlapped command, the DRV bit may be
changed to select another device and issue a command.

•

Changing the DRV bit while BSY or DRQ are set may cause the currently selected device to abort any command in
progress.

•

The normal protocol for Non-Overlapped commands requires that the command complete before the host can select
another device. This means that the host will not be able to access the Overlapped device again until the non overlapped device completes any command the host may issue to it.

•

To ensure fairness between slower Overlapped and faster Non-Overlapped devices sharing the same ATA channel, the
host should poll the slower Overlapped devices SERVICE bit before issuing each new command to the faster nonOverlapped device.

•

When the host detects that the SERVICE bit in the ATAPI STATUS Register is set, a Service (A2h) command shall
be issued before any task file registers besides ATAPI STATUS are valid.

•

Slower Overlapped devices may release control of the ATA bus several times while processing an overlapped command.

•

DMA Operation for an overlapped command will make use of a new protocol. This “Overlapped DMA protocol” will
cause the ATA bus to be released after a specified number of data bytes have been transferred.

•

When DMA data is to be transferred, the protocol sequence used for PIO will be followed. When data is to be transferred a Service Interrupt will be generated. No data will be transferred until the Service (A2h) command has been received by the Device.

•

The number of bytes that will be transferred is specified in the BYTE COUNT Register after the Service (A2h) command has been processed. After the specified number of bytes is transferred the ATA bus shall either be released or
held busy until data or status are available.

•

At the completion of data transfer or within 5µs, either a Release or a Back-to-back data transfer shall be initiated.

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ATAPI Protocol
Overlapped Command Operation

5.17.1 Release
One of the capabilities that is the foundation for Overlapped operation is Release. There are three different forms of release used in this specification, after the receipt of a Command, after transferring some data and after the receipt of the
Service Command.
This specification will allow the device to implement these release operations either in the Firmware or in Hardware.
Each of these release points has its own complexities. For example before the Task File Registers can be released after
the receipt of a command, the Command and parameter information must be saved. Once the release is performed the
contents of the Task File Registers can no longer be used by the Device. Although this save would seem simple, adding
a complete set of shadow registers is expensive and will not allow the device to perform command queueing that may be
proposed in future versions of this specification. For command queuing there must be separate registers/memory locations for each of the commands that can be queued. Thus if the device supports 16 commands, then 16 back to back commands could be sent to the device by the host faster then the device could process them. The device could have only one
set of shadow registers and only automatically release the Task File Registers when moving the standard set into the
shadow set, but this would incur delays for release when the second command was loaded if the first had not yet been
processed by the device. This would thus cause inconsistent delays until the Task File Registers were released.
This specification assumes the device will consistently unload the information in the Task File Registers. Although holding the BSY longer in some cases would most likely be acceptable from a system performance standpoint, forcing the
driver to poll for varying lengths of time is not. This specification forces the device to report the typical length of time
that the device will require to unload and then Release the Task File Registers. Further to reduce the length of time that
the Driver would have to poll for the Release, this specification has an Interrupt on Release Capability.
The Interrupt on Release capability is enabled by the Host Driver using a SET FEATURES Command. To assist the
Driver in determining if the Interrupt should be enabled the IDENTIFY DRIVE Command returns the length in microseconds that the device will use to Release for both an Overlapped Command and the Service Command. The Driver can
then make its own decision to enable the interrupt. Thus if the Device reports 1000 µs, the Driver could decide that it
wants to poll and not enable the interrupt (Unlikely).
The Release after the transfer of data shall be performed by hardware for all data transfer operations and as such there is
no Interrupt generated after the release when transferring data. An optional Back-to-Back Data Transfer without a Release or IRQ can be used by a device.

5.17.2 Service Command (A2h)
The Arbitration of the Task File Registers is performed by logic outside of the Devices attached to the ATA Cable. The
basic premise is that the Device releases the use of the Task File Registers when it is processing the command and no
longer needs the registers. This of course makes it difficult to place the arguments for the Interrupt into the registers as
the device no longer owns them. The Service command essentially hands the registers back to the device so that the correct parameters can be placed into them. These parameters include the Byte Count, and Interrupt Reason.
The Clearing of Busy after the Service Command shall only occur after the parameters for the Interrupt are loaded into
the Task File Registers. Thus for a hardware implementation of this Clearing of Busy, there should exist a separate set of
information for these parameters e.g. Byte Count, Interrupt Reason, Status. Note, in the future, acceleration of the Service Command will become very important to the overall system performance when using overlap. It is highly recommended that the time required to perform the Clearing of Busy after the SERVICE Command is less than 5µs.
When an overlapped command requests service the Host Driver is responsible for determining which device should be
serviced, and then issuing the Service Command. This causes the device to place information on the reason for the service into the Task File registers.

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ATAPI Protocol

Addr
esses

Register

1F0
1F1
1F1
1F2
1F3
1F4
1F5
1F6
1F7

Data
Error Register
Reserved for ATA Tag
Interrupt Reason
Tag for Command
ATAPI Byte Count LSB
ATAPI Byte Count MSB
Drive Select
Status

3F0
3F1
3F2
3F3
3F4
3F5
3F6
3F7

Floppy A Status
Floppy B Status
Unused
Floppy ID / Tape Control
Floppy Controller Status
Floppy Data Register
Alternate Status
Change / Drive Address

Contents After Service Command Completes

If the Status indicates an Error then this is Valid
Reserved and not used by this Specification.
Contains IO and CoD
Contains the Tag for the command requiring Service
Number of bytes that need to be transferred, both for
PIO or for DMA
Same before and after “Service”
DRQ along with IO, Cod and Release determine the
reason for the Service Request

Unused

Same as Status register
Same before and after “Service”

Table 4 - Registers after the Service Command

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ATAPI Protocol
Overlapped Command Operation

5.17.3 Overlapped Operation, Legal Transitions

Table 5 - Legal Transitions for Overlapped Operation
State From

State To

Reason

Idle

Cmd Packet

Host Issues A0h

Cmd Packet

Release

Command ok, but no
data is ready to be transferred

Cmd Packet

Data Transfer

Data Transfer

Release

Data Transfer

Data Transfer

Command ok and Data
is ready to be Sent/
Received
# of bytes specified by
the Byte Count Register has been transferred
# of bytes specified by
the Byte Count Register has been transferred

Release

Service

Service

Data Transfer

Service

Status

Service Command
issued and Status is
available

Data Transfer

Status

# of bytes specified by
the Byte Count Register has been transferred

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Data or Status is ready
for the Host
Service Command
issued and Data can be
transferred

Sequence
BSY=1, CoD=1, IO=0,
DRQ=1, BSY=0
BSY=1, DRQ=0,
RELEASE=1, CoD=0, IO=0,
BSY=0, INTRQ=1 if Interrupt
on Release After Command
Packet is enabled
BSY=1, DRQ=0, CoD=0,
IO=1/0, RELEASE=0,
DRQ=1, BSY=0, INTRQ=1
RELEASE=1, DRQ=0 (BSY
stays=0, CoD & IO Stay the
same)
BSY=1, DRQ=0, Byte Count =
new count (CoD & IO stay the
same), DRQ=1, BSY=0,
INTRQ=1
SERVICE=1, DMA
READY=0/1, INTRQ=1
BSY=1, IO=1/0, CoD=0, Byte
Count=x, DRQ or DMARQ=1
(DMA READY stays the
same), BSY=0, INTRQ=1 if
Interrupt on Service Completion is enabled
BSY=1, IO=1, CoD=1,
RELEASE=0, DRQ=0,
BSY=0, INTRQ=1 if Interrupt
on Service Completion is
enabled
BSY=1, RELEASE=0, DRQ or
DMARQ=0, CoD=1, IO=1,
BSY=0, INTRQ=1

Notes

The time required by the Device
to perform the Release is specified
in Word 71 of the Identify Drive
Data
The assertion of DRQ shall occur
within the time specified in word
71 of the Identify Drive Data
The Release shall occur within
5µs after transferring the last
word of data
The assertion of DRQ shall occur
within 5µs after transferring the
last word of data from the previous data transfer
Requests that the Host Arbitrate
and Issue the Service Command.

This is not a recommended transition. After transferring the data
the device should set BSY until
the status is available
BSY shall be set within 5µs after
transferring the last word of data
if status will not be available
within the 5µs window

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ATAPI CD-ROM Specification
ATAPI Protocol

Init
IDLE

Cmd Packet

A0 Received

Error or Completion
Not processing
any commands

Accept Command
Packet from
Host
No Data to Transfer

Service
Release

Data Ready to Transfer
Wait for
Service Cmd

Clear BSY
Optional INTRQ
Data Ready

Data Xfer
Service

Set DRQ or DMARQ
and Interrupt

No Data to Transfer
All Data Transferred
Status is Ready
Note: This path is used for Non-data
transfer commands

Back-to-back Data Transfer
within the 5µs limit

Service
Wait for
Service Cmd
All Data Transferred
Status is Ready

Service
Status
Interrupt
with valid
Status

Status is available, Non-data transfer Command
or and Error on the Command Packet

Figure 8 - State Diagram, Overlapped Operation

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ATAPI Protocol
Overlapped Command Operation

Host

Device
ATAPI

Wait for Not Busy
Load Task File with Byte Count & Features
Write A0 (Packet) Command
[Wait for not Busy]

ATA Drive

Set Busy
Read Task File Values
Set Interrupt Reason = Packet
Clear Busy

Write six words of Packet Data

[Wait for Interrupt]

Set Busy
Get Packet Data
Check Command for Validity
Set Interrupt Reason = Release
Clear Busy
Set Interrupt

Check for Release Interrupt
If there are ATA Disk Command(s) available:
One Complete
Command to
an ATA Disk

Set Task File Registers
with Sector Count/Number/Cylinder/Head/DRV
Issue the ATA Command (e.g. Read PIO)
[Wait for Interrupt]
Read the Status
Transfer the Data

Set Busy
Process Command
Set DRQ, Clear Busy, Set Interrupt
Clear DRQ

Reselect the ATAPI Drive
[Wait for Interrupt or New ATA Command]
New
ATA Command

[Ready to Transfer Data]
Set Service Status Bit
Set Interrupt

Read the Status and look for Service Bit
Issue A2h (Service Command)
[Wait for not Busy]

Set Busy
Set Byte Count, Interrupt Reason = Data
Set DRQ and Clear Busy

Read the Interrupt Reason Register and Byte Count
Transfer the Data

[Wait for Interrupt]

Set Busy, Clear DRQ
Set Status, Interrupt Reason = Status
Clear Busy and Set Interrupt

Read the Interrupt Reason Register and look for Status

Figure 9 - ATAPI Overlap, One ATA Device and One ATAPI Device

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ATAPI Protocol
5.17.4 Task File ownership
When BSY or DRQ is set, the Task File Registers are owned by the Device, otherwise the Registers are owned by the
Host. When the Device does not own the Registers, it shall not write to into them. The "Table 6 - Registers Controlled
by BSY & DRQ" on page 45 shows which of the ATA Registers are considered part of the “Owned” Task File Registers.

Logic conventions are:

A = signal asserted, N = signal negated, x = does not matter which it is.
Dark Gray are registers where ownership is controlled by BSY & DRQ.
Light Gray are Registers that are not defined for use by ATA.

Addresses

Functions

CS1FX

CS3FX

DA2

DA1

DA0

A
A
A
A
A
A
A
A
N
N
N
N
N
N
N
N

N
N
N
N
N
N
N
N
A
A
A
A
A
A
A
A

0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1

0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1

0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1

Read (DIOR-)

Write (DIOW-)

Data
Error Register
Features
ATAPI Interrupt Reason / Sector Count
Sector Number
ATAPI Byte Count LSB / Cylinder Low
ATAPI Byte Count MSB / Cylinder High
Drive Select
Status
Command
Floppy A Status
Unused
Floppy B Status
Unused
Unused
Floppy Digital Output
Floppy ID / Tape Control
RESERVED
Floppy Controller Status
RESERVED
Floppy Data Register
Alternate Status
Device Control
Change / Drive Address
Unused

Table 6 - Registers Controlled by BSY & DRQ

5.17.5 Error Handling with Overlapped Commands
An issue can arise with because overlapped commands are enabled on a Command by Command basis. If an overlapped
command is in progress and a non-overlapped command is then received, the Device must abort without any status any
outstanding overlapped command.
In overlapped operation there will be intermediate command status, as well as the final command completion status. The
intermediate status is supplied to indicate if the command was accepted. If the command is not accepted, then there will
be no further status supplied. The intermediate status is the status at the point that the device releases the Task File registers back to the host, prior to executing the command. Thus this status can only relate to the validity of the command and
not any command execution.

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ATAPI Protocol
BIOS and ATAPI Driver Compatibility

5.18 BIOS and ATAPI Driver Compatibility
This section discusses the IDE features and functions that shall be provided by the ATA Device to allow the BIOS and
driver to be content.

5.18.1 Reset Master/Slave Diagnostics Sequence
A Reset Master/Slave Diagnostics Sequence with a Good Status shall be provided or the BIOS will not continue. When
the CD-ROM is the slave device, and it does not respond after the Reset or Diagnostic Commands, the Master Device
will return an Error Condition to the Host Computer and all will die.

5.18.2 SRST Initialization Sequence
The SRST bit in the ATAPI Device Control Register (See “Table 17 - ATAPI Device Control Register (ATA Device Control Register)” on page 57) shall NOT be used by the ATAPI Driver (except for power management when SRST is used
to wake up an ATAPI device). Instead the ATAPI Device Driver shall reset the ATAPI Device utilizing the ATAPI Soft
Reset command (see “6.2 ATAPI Soft Reset Command and Protocol” on page 50). Resetting the ATAPI Device using the
ATA SRST would also reset any ATA hard drive attached, and if there are separate Drivers for an IDE and an ATAPI device, each driver would be resetting the others peripheral without the other driver being aware of the reset.

5.18.2.1 SRST Sequence Device 0
1.

Host sets SRST bit to one.

2.

Device 0 sets BSY within 400 nsec.

3.

Device 0 Posts diagnostic results in the Error Register.

4.

Device 0 waits for the Host to clear SRST to zero.

5.

If Device 0 detected that Device 1 is present during the most recent power on or hardware reset sequence, then
Device 0 waits up to 31 seconds from the time that SRST bit became zero for Device 1 to assert PDIAG-. If PDIAG- is asserted within 31 seconds, Device 0 clears bit 7 of the Error Register to zero, else Device 0 sets bit 7 equal
to one in the Error Register. If Device 1 was not detected in the most recent power up or hardware reset sequence,
then Device 0 clears bit 7 of the Error Register to zero.

6.

Device 0 loads the ATAPI Signature into the Task File Registers.

7.

Device 0 Clears the BSY bit to zero when ready to accept commands within 31 seconds after the SRST bit was
cleared to zero.

5.18.2.2 SRST Sequence Device 1
1.

Host sets SRST bit to one.

2.

Device 1 sets BSY within 400 nsec.

3.

Device 1 negates PDIAG- within 1 msec after SRST is set to one.

4.

Device 1 Posts diagnostic results in the Error Register.

5.

Device 1 waits for the Host to clear SRST to zero.

6.

Device 1 loads the ATAPI Signature into the Task File Registers.

7.

Device 1 Clears the BSY bit to zero when ready to accept commands within 31 seconds after the SRST bit was
cleared to zero.

8.

If Device 1 didn’t post any error, assert PDIAG-, else optionally assert PDIAG-.

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5.18.2.3 Other SRST Related Issues
A value other than 00h in the status register prior to the receipt of the first ATAPI Command Packet from the host may
cause ATAPI Devices to be incorrectly identified by pre-ATAPI host BIOS as an ATA-compatible disk drive.
Initializing the task file upon receipt of an SRST works since only immediate commands will be executing when an ATA
disk driver issues an SRST. To prevent interruption of ATAPI immediate commands which have not finished executing,
the function of the DSC bit (i.e. command complete) shall be maintained. On a warm boot the BIOS and/or drivers may
see a status of 00h or 10h, depending on whether or not an ATAPI immediate command completed at the same time the
system performed the WARM BOOT.
The signature placed in the task file following an SRST shall remain until the ATAPI device receives its first ATAPI
command, i.e., the ATAPI device will look NOT READY (DRDY=0). This will not affect the ATAPI device drivers
ability to send ATAPI commands to the ATAPI device since it is not required to wait for DRDY=1. However, it will prevent ATA-compatible drivers, such as those performing power management, from sending commands to an ATAPI device until the ATAPI device has received its first ATAPI command: ATAPI Packet Command, ATAPI Identify Device,
ATAPI Soft Reset.
ATAPI drivers wishing to use ATA power management commands must poll DRDY and, if it is not set, they must also
look at the Cylinder registers for the ATAPI signature. If the signature is present, the ATAPI driver must issue the ATAPI device an ATAPI command, re-enabling DRDY, before it can issue an ATA Power management command. Operating systems wishing to use a common ATA power management driver must also be changed to perform this detection
and recovery sequence, if they intend to power-manage ATAPI devices.

5.18.3 Special Handling of ATA Read and Identify Drive Commands
ATAPI drivers shall not issue SRST since it may corrupt the state of ATA IDE drives sharing the same cable. Instead,
ATAPI drivers shall use the ATAPI Soft RESET command to initialize an ATAPI device. Note that ATAPI commands
shall not be issued to a device which has not already been identified as an ATAPI device. In order to provide ATAPI
drivers with the ability to force a device to initialize its ATAPI signature (Cylinder High = EBh, Cylinder Low = 14h)
without issuing an SRST, ATAPI devices shall abort the ATA Read and Identify Drive commands and initialize the task
file with the ATAPI signature before clearing BSY.

5.18.4 ATAPI aware BIOS and Driver Considerations
Pre-ATAPI BIOS will not detect or configure ATAPI devices. Some of these BIOS are capable of configuring ATA
hard disks for ATA Mode 3 IORCHDY operation. This places a special burden on ATAPI drivers to detect the presence
of any ATA disk drives sharing the same port address and configure the ATAPI device for a compatible mode of operation.
Note that a special IDE port configuration driver must be provided by the IDE card manufacturer to configure the cards
proprietary IDE configuration control registers. These proprietary IDE card drivers should be loaded before the ATAPI
driver.
During ATAPI device detection, ATAPI device drivers or ATAPI-aware BIOS should verify that Status=00h (Not BSY,
Not RDY) and that the ATAPI signature Cylinder High = EBh, Cylinder Low = 14h are present. If an ATAPI device is
detected, then issue an ATAPI Identify Command to complete the ATAPI detection protocol and re-enable the task file
(DRDY=1). If the device is ready to accept an ATA command, but no ATAPI signature is detected, then issue an ATA

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ATAPI Protocol
BIOS and ATAPI Driver Compatibility

Read or Identify Drive command to the device to force the ATAPI device to initialize its signature. Then wait for BSY=0
and re-verify the presence of the ATAPI signature. If there is still no ATAPI signature present, do not configure the device.
ATAPI-aware BIOS and drivers should give special attention to managing configurations where ATAPI drivers share an
IDE port address (Cable) with ATA IDE drives and their drivers. ATA IDE drivers frequently issue SRSTs to manage errors thereby causing ATAPI devices to clear DRDY as part of their SRST ATAPI signature initialization sequence. If
the ATAPI driver already knows that the device it wishes to issue an ATAPI command to is an ATAPI device, then it
need not take special action since issuing any of the ATAPI commands which do not require DRDY=1, will restore the
ATAPI device’s ability to accept ATA commands. If, however, the ATAPI driver wishes to issue an ATA command to
an ATAPI device which has received an SRST from an ATA IDE driver, it should issue the ATAPI device an ATAPI
Soft Reset to restore the ATAPI device’s ability to accept ATA commands.
Note that “Newer” BIOS detect the presence of a Drive (see "4.3 ATA Compatibility" on page 17) by using the IDENTIFY DRIVE command, but older BIOS use configuration information from outside the IDE/ATA interface. It has also
been discovered that very old BIOS may issue an ATA READ command to detect the presence of an ATA IDE drive.
Therefore, the ATA READ and IDENTIFY DRIVE commands shall be aborted by ATAPI Devices. It has also been discovered that some BIOS look at the status register to detect the presence of an ATA drive.
Implementer’s Note: Implementers of ATAPI drivers which are intended to share a single cable with a disk and disk
driver should ensure that the device has completed any issued commands prior to changing the DRV bit.

5.18.5 Default Timing
It is recommended that ATAPI devices compatible with this specification, support ATA mode 3 timing without requiring the host system to configure the ATAPI device using any set features commands. ATAPI devices should therefore either be fast enough to always supply data at the maximum rate allowed by Mode 3 or the ATAPI device must be shipped
with IORDY enabled.
ATAPI devices shall revert to their default interface configuration on a Power On Reset or a Hardware Reset.
Implementer’s Note: A Non-Overlapped low-speed drive, Mode 0-2, may affect system performance when sharing the
same cable with hard disk drives capable of mode 3 or faster data transfer timing.

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ATAPI Transport Mechanism

6.0 ATAPI Transport Mechanism
The Transport Mechanism provides for the hardware support to connect the host computer to the Peripheral.

6.1 Reset Conditions
There are three types of Reset Condition to which ATAPI Devices shall respond:
•

Power On Reset or Hardware Reset: the Device executes a series of electrical circuitry diagnostics and sets default values, as well as executing the Master Slave Diagnostic Protocol.

•

ATAPI Soft Reset: ATAPI Devices shall reset the interface circuitry according to the Set Features requirement upon receipt of the ATAPI Soft Reset Command.

•

ATA SRST: ATAPI Devices shall provide the normal ATA PDIAG/ DASP sequence and initialize the task file with the ATAPI signature upon detection of SRST. No actual reset of the ATAPI
device will occur, no commands that may be active will be aborted or stopped.

The Reset Conditions above are listed in order of precedence. That is, Power On or Hardware Reset shall take precedence over ATAPI Soft Reset, which shall take precedence over ATA SRST, which shall take precedence over all other
conditions.

6.1.1 Power On or Hardware Reset
Each ATAPI Device, as it is powered on, shall perform appropriate internal reset operations, and internal test operations.
ATAPI Devices upon detection of reset, shall:
1.

Clear all Commands and I/O operations in progress.

2.

Return to Devices default configuration.

3.

Perform the DASP / PDIAG sequence (See "Figure 10 - DASP / PDIAG Sequence after Hardware Reset or Power
On" on page 50).

4.

Return any ATAPI Device operating modes to their appropriate initial conditions, similar to those conditions that
would be found after a normal power-on reset. MODE SELECT conditions shall be restored to their last saved
values if saved values have been established. MODE SELECT conditions for which no values have been saved
shall be returned to their default values.

5.

Initialize the Task File Registers as follows: Status = 00h, Error = 01h, Sector Count = 01h, Sector Number = 01h,
Cylinder Low = 14h, Cylinder High =EBh and Drive/Head = 00h. A value other than 00 in the status register prior
to the receipt of the first ATAPI Command Packet from the host may cause the ATAPI Device to be incorrectly
identified by the host as an ATA compatible disk drive. BSY = 0, following any Reset, indicates to the Host that
the registers within the Task File have been initialized.

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Host Computer

Master (Drive 0)

ATAPI Transport Mechanism
ATAPI Soft Reset Command and Protocol

Slave (Drive 1)

Hardware or Power On Reset
Sets Busy, clears DASP & PDIAG

Sets Busy, clears DASP & PDIAG
Within 1ms assert DASP

Waits up to 450 ms for Slave to assert DASP
Within 30 seconds deassert Busy
and assert PDIAG
Wait up to 31s for PDIAG to be asserted

Clear Busy

After 31 seconds or next command
Deassert DASP

Figure 10 - DASP / PDIAG Sequence after Hardware Reset or Power On

6.2 ATAPI Soft Reset Command and Protocol
ATA specifies a mandatory software reset capability because it provides a recovery mechanism from a class of errors/
problems that are recoverable in no other way. The current CD-ROM drivers invoke this feature at some point in their error recovery procedures today.
The ATA software reset mechanism, SRST, (bit 2 in the Device Control Register) cannot be used for ATAPI Devices,
because resets issued by the ATAPI driver would also reset any attached hard disk and vice versa.
For a software reset to be useful, it must be able to bring the drive’s microprocessor back from a busy or hung condition,
allowing issuance of a diagnostic or some other command. Since the microprocessor is the destination of the reset, we
can’t depend on it as part of the reset path. Therefore, ATAPI Soft Reset shall be detected/decoded by the interface controller circuitry and be routed back to the microprocessor as a hardware signal.
Upon detection of the ATAPI Reset command, shall:
1.

Set BSY. When the reset sequence in the Device is complete the Busy status will be cleared. This will be the only
status returned to the host by the ATAPI Soft Reset command.

2.

Initialize the task file with the same information as after a Power On Reset. See section 6.1.1, "Power On or Hardware Reset", on page 49 for a description of the initialization sequence, with the exception of the DRV bit which
shall remain unchanged.

6.3 ATAPI Implementation of ATA SRST
The ATA software reset mechanism, SRST, (bit 2 in the Device Control Register) cannot be used for ATAPI Devices,
because resets issued by the ATAPI driver would also reset any attached hard disk and vice versa. To solve this ATAPI
defines an ATAPI Soft Reset command using a reserved ATA opcode which could be decoded by the interface controller
hardware.

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ATAPI Transport Mechanism

To maintain Master / Slave compatibility with ATA disk drives and prevent detection of ATAPI Devices by non ATAPIaware BIOS, ATAPI Devices shall implement the following upon receipt of an ATA SRST:
1.

Perform SRST PDIAG sequence see "5.18.2 SRST Initialization Sequence" on page 46.

2.

Initialize the task file with Status = 00h or 10h, Error = According to SRST Sequence, Sector Count = 01h, Sector
Number = 01h, Cylinder Low = 14h, Cylinder High =EBh and Drive/Head = 00h. Note that Device 0 will be seleted after the completion of the SRST sequence.

3.

The functionality of the DRDY and DSC bits shall be restored on the first command following an SRST.

4.

Continue executing commands or play operations.

5.

Leave Mode settings or Set Feature settings unchanged.

6.

If a selected ATAPI Device detects SRST while its own DRQ or BSY is set (1), then the command in progress
shall be stopped.

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ATAPI Transport Mechanism
Physical Connection

6.4 Physical Connection
The ATAPI Devices are selected by the Address field in the Drive Select Register. When the ATAPI Device is attached
along with an ATA Mass Storage Device, the ATAPI Device should be set as Device 1 and respond as a Slave.

Table 7 - Preferred Drive Connection
Primary Cable
Drive 0

Secondary Cable
Drive 1

ATA
ATA

Drive 0

Drive 1

ATAPI

ATA

ATAPI

ATA

ATAPI

ATAPI

Notes
Normal, no ATAPI
Disk and CD-ROM for
enhanced IDE system
Legacy IDE System with
only one cable
Enhanced IDE with CDROM and a tape or two CDROMs

6.5 Single Drive Configurations
There can be either one or two drives attached to the ATA Cable, and thus four configurations are possible. Even though
there are four possible configurations, only three of them are recommended. An ATAPI Peripheral shall detect each of
these three configurations and respond according to "Table 8 - Shadow Registers" on page 52.
There are configurations where there may be only one Master or Slave present on the cable. In this case there will be a
“Shadowing” of the registers for the non-existent device. The following table shows the actions to take.

Table 8 - Shadow Registers
Jumper ->
Master

Slave

CSEL=M

CSEL=S

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Device

Configuration

0
1
1
0
0

Don’t Care
Slave Present
Slave Not Present
Master Present
Master Not Present

1
0
1
1
0
0

Don’t Care
Don’t Care
Slave Present
Slave Not Present
Master Present
Master Not Present

1

Don’t Care

Action
Drive Bus
Float Bus
Shadow
Float Bus
This is not a recommended Configuration.
Float Bus
Drive Bus
Drive Bus
Float Bus
Shadow
Float Bus
This is not a recommended Configuration.
Float Bus
Drive Bus

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ATAPI Transport Mechanism

Table 9 - Shadowing for Single Drive Configurations
Drive 0
Register Description

Drive 1 (Non-existent Slave) Use of the Register
Control Block Registers

Alternate ATAPI Status

This may be either be a complete duplicate of the Drive 0 Status
(Shadowed) or Some of the bits are explicitly for Drive 1 (e.g.
ERROR)

Device Control

Writing to this register writes to Drive 0’s Device Control Register

Command Block Registers
Data

Should not be used for the non-existent slave

ATAPI Error Register

This may be either be a complete duplicate of the Drive 0 ATAPI Error
Register or the Register is explicitly for Drive 1 (Not Shadowed)

ATAPI Features

Writing to this register writes to Drive 0’s ATAPI Features Register

ATAPI Interrupt Reason Register
ATAPI Byte Count Register (bits 0-7)
ATAPI Byte Count Register (bits 8-15)

These are an exact duplicate of Drive 0’s register. Implementer’s
Note: As the Signature is placed in these Registers, both Drive
0, and the non-existent Drive 1 will have an “ATAPI Signature” after a reset condition. To detect that Drive 1 does not
exist will require a command be issued to Drive 1 and detecting
the Abort.

Drive Select

Writing to this register writes to Drive 0’s Drive Select Register

ATAPI Status

This may be either be a complete duplicate of the Drive 0 Status
(Shadowed) or Some of the bits are explicitly for Drive 1 (e.g.
ERROR)

ATA Command

Commands to Drive 1 will be aborted. Implementer’s Note: The
Error bit will need to be set to abort a command to Drive 1, if
the Status and Alternate Status Registers are complete shadows
of Drive 0’s Register, changing the DRV bit and reading the
Status Register will also show an error condition that does not
exist. It is recommended that the ERROR bit not be shadowed,
but a separate bit for the non-existent drive 1.

Implementer’s Note: Drive 0 (Master) is able to determine if Drive 1 (Slave) is present, but Drive 1 can’t determine if
Drive 0 is present. Drive 0 will see the Slave drive assert the DASP- signal during the Reset procedure, which indicates
that the Slave is present.

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ATAPI Transport Mechanism
Register Mapping

6.6 Register Mapping
Communication to or from the Devices is through I/O Registers that route the input or output data to or from registers
(selected) by a code on signals from the host (CS1FX-, CS3FX-, DA2, DA1, DA0, DIOR- and DIOW-).

6.7 ATAPI Register Map (Packet Command)
Logic conventions are:

A = signal asserted, N = signal negated, x = does not matter which it is

Table 10 - I/O Port Functions/Selection Addresses (Compatibility Model)
Addresses
CS1FX

CS3FX

DA2

Functions
DA1

DA0

Read (DIOR-)

Write (DIOW-)

Control Block Registers
N

A

0

0

0

Floppy A Status

Unused

N

A

0

0

1

Floppy B Status

Unused

N

A

0

1

0

Unused

Floppy Digital Output Register

N

A

0

1

1

Floppy ID / Tape Control

RESERVED

N

A

1

0

0

Floppy Controller Status

RESERVED

N

A

1

0

1

N

A

1

1

0

Alternate ATAPI Status

Device Control

N

A

1

1

1

Note1

Not Used

Floppy Data Register

Command Block Registers

1.

A

N

0

0

0

Data

A

N

0

0

1

ATAPI Error Register

ATAPI Features

A

N

0

1

0

ATAPI Interrupt Reason Register

Unused

A

N

0

1

1

Reserved For SAM TAG Byte

A

N

1

0

0

ATAPI Byte Count Register (bits 0-7)

A

N

1

0

1

ATAPI Byte Count Register (bits 8-15)

A

N

1

1

0

Drive Select

A

N

1

1

1

ATAPI Status

ATA Command

This register is obsolete. It is recommended that a device not respond to a read of this address. If a device does
respond, it shall not drive the DDF signal.

With the exception of the Data Register, all the ATAPI registers are referenced using Byte (8 Bit) Read and Writes. The
Data Register is ALWAYS referenced as a 16 bit word.

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Table 11 - ATAPI Status Register (ATA Status Register)
D7

D6

D5

D4

D3

D2

D1

D0

BSY

DRDY

DMA
READY
or DF

SERVICE
or DSC

DRQ

CORR

Reserved

CHECK

Read

DRDY, DSC, CORR and CHECK shall only be valid at the end of the completion of the command.
Bit 7

BSY

Busy is set whenever the drive has access to the Command Block.

Bit 6

DRDY

Indicates that the drive is capable of responding to an ATA command.

Bit 5

DMA READY / DF

This bit indicates that the device is ready to start a DMA data transfer. This
bit is reserved for future more advanced overlap capabilities.
Note that this bit is used for Drive Fault (DF) when Overlapped or Interleaved DMA operation is not enabled.

Bit 4

SERVICE / DSC

This bit signals that the device is requesting service or interrupt. It is set when
the interrupt is requested and does not clear until the Service (A2h) command
is issued.
Note that this bit is used for the DSC function when the overlap function is
not enabled.

Bit 3

DRQ

Data Request - Indicates that the device is ready to transfer a word or byte of
data between the host and the drive. The information in the ATAPI Interrupt
Reason will also be valid during a Packet Command when the DRQ is set.

Bit 2

CORR

Indicates if a Correctable Error occurred.

Bit 0

CHECK

Indicates that an error occurred during execution of the previous command.
The bits in the Error Register contains the Sense Key and Code.

Table 12 - ATAPI Error Register (ATA Error Register)
D7

D6

D5
Sense Key

D4

D3

D2

D1

D0

MCR

ABRT

EOM

ILI

Read

Bits 7-4

Sense Key

The sense key is defined in "Table 140 - Sense Key Descriptions" on page 183.

Bit 3

MCR

Media Change Requested, is used and defined as in the ATA Standard.

Bit 2

ABRT

Aborted Command, is used and defined as in the ATA Standard.

Bit 1

EOM

End Of Media Detected.

Bit 0

ILI

Illegal Length Indication.

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ATAPI Register Map (Packet Command)

Table 13 - ATAPI Feature Register (ATA Feature Register)
D7

D6

D5

D4

D3

D2

Reserved

D1

D0

OVERLAP

DMA

Write

Bit 7-1

Reserved

Reserved for future enhancement.

Bit 0

DMA (Optional)

Any data for the Command will be transferred via the DMA interface. Note
this does not apply for the Command Packet.

Bit 1

OVERLAP (Optional)

The device may release the ATA bus before this command has completed. Release of the ATA bus is at the discretion of the device.

Table 14 - ATAPI Byte Count Register (ATA Cylinder High/Low Register)
D7

D6

D5

D4

D3

D2

D1

D0

Byte Count (Bits 0-7)

R/W

Byte Count (Bits (8-15)

R/W

The Byte Count is used for PIO only. The count shall be set prior to the issuance of the Packet Command. The count
contains the total transfer size for commands that transfer only one group of data (e.g. Mode Sense / Select, Inquiry) For
commands that require multiple DRQ Interrupts (e.g. Read, or Write) the count is set to the desired transfer size. When
any data is to be transferred, the ATAPI Device will set the Byte Count to the amount of data that the Host shall transfer
and then issue the DRQ Interrupt. The contents of this register shall not be changed until the first word is transferred to/
from the data register. Once the data transfer has been started, the device is allowed to change the contents of the byte
count (to set up the next transfer).

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Table 15 - ATAPI Interrupt Reason Register (ATA Sector Count Register)
D7

D6

D5

D4

D3

Reserved

D2

D1

D0

RELEASE

IO

CoD

Read

Bit 0

CoD

Command or Data. When this bit is zero then the information being transferred is user data, when one then the data is Command.

Bit 1

IO

Direction for the Information transfer, where in to the Host is indicated by a
value of one and out to the device is zero.

Bit 2

RELEASE

IO
0
1
1

DRQ
1
1
1

0

1

1

0

CoD
1
Command - Ready to Accept Command Packet Bytes
1
Message (Future) - Ready to Send Message data to Host
0
Data To Host- Send command parameter data (e.g. Read
Data) to the host
0
Data From Host - Receive command parameter data (e.g.
Write Data) from the host
1
Status - Register contains Completion Status

Release indicates that the device has released the ATA bus before completing
the command in progress.

Table 16 - ATAPI Drive Select Register (ATA Drive / Head Select Register)
D7

D6

D5

D4

1

Reserved

1

DRV

Bit 4

DRV

D3

D2

D1

D0

Reserved for SAM LUN

R/W

This bit selects either Device 0 (DRV=0) or 1 (DRV=1).

Table 17 - ATAPI Device Control Register (ATA Device Control Register)
D7

D6

D5
Reserved

D4

D3

D2

D1

D0

1

SRST

nIEN

0

Write

Bit 2

SRST

This bit is the Software Reset. The ATAPI Device shall follow the reset sequence for SRST defined in "6.3 ATAPI Implementation of ATA SRST" on
page 50. There is also a new reset capability for ATAPI Devices utilizing a
RESET COMMAND (see "6.2 ATAPI Soft Reset Command and Protocol" on
page 50).

Bit 1

nIEN

This bit enables/disables the interrupt to the host. When nIEN=0 and the device is selected, INTRQ shall be enabled through a tri-state buffer. When
nIEN=1 or the device is not selected, the INTRQ signal shall be in a high impedance state

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ATAPI CD-ROM Specification
CD-ROM ATA (Task File) Commands

7.0 CD-ROM ATA (Task File) Commands
7.1 ATA (Task File) Command Implementation Requirements
This section details the Commands that the CD-ROM Device shall support from the ATA Standard definition of the commands. All ATAPI commands, other than the “A0” ATAPI Packet Command, shall use the protocol described in the ATA
948 Document.

Table 18 - ATA Command and Status Usage for ATAPI CD-ROM Devices
Command

used Code

Error Register
BBK

Acknowledge Media Change

N

DB

ATAPI Soft Reset

M

08

Boot - Post-boot

N

Boot - Pre-boot

UNC

IDNF

ABRT

Status Register
TKONF

AMNF

DRDY

DWF

DSC

CORR

ERR

V

V

DC

V

V

N

DD

V

V

Check Power Mode

M

E5

V

Door Lock

N

DE

V

V

Door Unlock

N

DF

V

V

Download Microcode

N

92

V

V

Media eject

N

ED

V

V

Special Drive Diagnostic Errors

V

V

V

V

V

V
V

V

Execute Drive Diagnostics

M

90

Format Track

N1

50

V

V

V
V

Identify Drive

N

EC

V

V

Idle

O

E3

V

V

V

V

V

V

V

V

V

Idle Immediate

M

E1

V

Initialize Drive Parameters

N1

91

V

NOP

M

00

V

ATAPI Pkt. Command

M

A0

ATAPI Identify Device

M

A1

V

V

Service

O

A2

V

V

Read Buffer

N

E4

V

V

Read DMA (w/retry)

N

C8

V

V

Read DMA (wo/retry)

N

C9

V

V

Read Long (w/retry)

N

22

V

V

Read Long (wo/retry)

N1

23

V

V

Read Multiple

N

C4

V

V

Read Sector(s) (w/retry)

1

N

20

V

V

Read Sector(s) (wo/retry)

N1

21

V

V

Read Verify Sector(s)
(w/retry)

1

N

40

V

V

Read Verify Sector(S)
(wo/retry)

N1

41

V

V

Recalibrate

N

1x

V

V

working draft ATAPI

Contains Packet Command Status

V
V

V

V

V
V

V
V
V

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CD-ROM ATA (Task File) Commands
ATA (Task File) Command Implementation Requirements

Table 18 - ATA Command and Status Usage for ATAPI CD-ROM Devices (Continued)
Command

used Code

Error Register
BBK

UNC

IDNF

ABRT

Seek

N

7x

V

Set Features

M

EF

V

Set Multiple Mode

N

C6

V

Sleep

M

E6

V

Status Register
TKONF

AMNF

DRDY

DWF

DSC

V

V

V

CORR

ERR

V
V
V
V

V

V

V

Standby

O

E2

V

V

V

V

V

Standby Immediate

M

E0

V

V

V

V

V

Write Buffer

N

E8

V

V

Write DMA (w/retry)

N

CA

V

V

Write DMA (wo/retry)

N

CB

V

V

Write Long (w/retry)

N1

32

V

V

Write Long (wo/retry)

N1

33

V

V

Write Multiple

N

C5

V

V

Write Same

N

E9

V

V

Write Sector(s) (w/retry)

N1

30

V

V

Write Sector(s) (wo/retry)

N1

31

V

V

Write Verify

N

3C

V

V

Invalid Command Code

V

V

V

V

V

V = valid on this command
Y = Used by the CD-ROM ATAPI Drive, as specified by the ATA Standard
N = Not supported by ATAPI CD-ROM Drives
M = Mandatory for ATA
Shaded = Commands utilized by the ATAPI CD-ROM Drive

1.

This command is specified as Mandatory for ATA, but shall NOT be supported by ATAPI Devices

7.1.1 ATAPI Soft Reset
Note: For performance reasons, a soft reset may not force reading of TOC.
See "6.2 ATAPI Soft Reset Command and Protocol" on page 50

7.1.2 Check Power Mode
This command checks the power mode.
If the drive is in, going to, or recovering from the Standby Mode, the drive shall set BSY, set the Sector Count Register to
0x00, Clear BSY, and generate an interrupt.
If the drive is in Idle Mode, the drive shall set BSY, set the Sector Count Register to 0xFF, clear BSY, and generate and
Interrupt.

7.1.3 Execute Drive Diagnostics
This command shall perform the internal diagnostic tests implemented by the drive. The DRV bit is ignored. Both
drives, if present, shall execute this command. See the ATA Standard (X3T9.2/791D) for more information.

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ATAPI CD-ROM Specification
CD-ROM ATA (Task File) Commands
Implementer’s Note: ATAPI device drivers issuing the Execute Diagnostics command will cause all ATA and ATAPI devices to execute a diagnostic command resulting in a device reset. To prevent unwanted resets and or driver compatibility issues, ATAPI drivers should not issue the Execute Diagnostics command. The command is implemented by ATAPI
devices for ATA compatibility only.

7.1.4 Idle Immediate
This command causes the drive to set BSY, enter the Idle Mode, clear BSY, and generate an interrupt. The interrupt is
generated even though the drive may not have fully transitioned to Idle Mode.

7.1.5 NOP
This command enables a host which can only perform 16-bit register accesses to check drive status. The drive shall respond as it does to an unrecognized command by setting Abort in the Error Register, Error in the Status Register, clearing Busy in the Status Register, and asserting INTRQ.

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CD-ROM ATA (Task File) Commands
ATA (Task File) Command Implementation Requirements

7.1.6 Packet Command
See section 5.2, "ATAPI PACKET Command", on page 21.

7.1.7 ATAPI Identify Device
The ATAPI IDENTIFY DEVICE command enables the host to receive parameter information from the drive. The parameter words in the buffer have the arrangement and meaning defined in the table below. All reserved bits or words shall be
zero. Although many of the fields of information returned by the ATAPI Identify Device command are inappropriate for
a CD-ROM drive, the fields that shall be returned with meaningful information are shown in "Table 19 - Identify Drive,
Fields Supported by CD-ROM".
Like all ATAPI commands (A0h, A1h and 08h), this command can be issued, regardless of the state of the DRDY. When
the command is issued, the device sets BSY, stores the required parameter information in the sector buffer, sets DRQ, and
generates an interrupt.
Implementer’s Note: ATAPI devices shall swap bytes for ASCII fields to maintain compatibility with ATA.” For example,
“This Example” would be written as “hTsiE axpmel.”

Table 19 - Identify Drive, Fields Supported by CD-ROM
Word

Bits

0
1
2
3
4
5
6
7-9
10-19
20
21
22
23-26
27-46
47
48
49

50
51
52
53

54 - 56
57-58
59
60-61
62

Page 62

15 - 2
1
0

15 - 8
7-0

Description
General Configuration
Cylinders
Reserved
Heads
Number of unformatted bytes per track - vendor specific
Number of unformatted bytes per sector - vendor specific
Number of sectors per track
Reserved
Serial Number
Vendor specific
Vendor specific
ECC bytes available
Firmware revision (18 ASCII characters)
Model Number (40 ASCII characters)
Multiple Sector Command, Sector Count
Reserved
Capabilities:
LBA bit shall be supported; DMA, IORDY, Overlap and
Standby bits are optional.
Reserved
PIO Cycle Timing
DMA Cycle Timing
Reserved
Fields in words 64-70 valid
Fields in words 54-58 valid
Current Cylinder/Heads/Sectors
Current Capacity
Reserved
User Addressable Sectors
Singleword DMA transfer mode active
Single word DMA transfer modes supported

Used
Mandatory
No
No
No
No
No
No
No
Optional
No
No
No
Mandatory
Mandatory
No
No
Mandatory

No
Mandatory
Mandatory
Mandatory

No
No
No
No
Mandatory

Fixed/Variable
Fixed

Fixed

Fixed

Fixed
Fixed
Fixed
Fixed
Variable

Variable
Fixed

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ATAPI CD-ROM Specification
CD-ROM ATA (Task File) Commands
Table 19 - Identify Drive, Fields Supported by CD-ROM (Continued)
Word
63

Bits
15 - 8
7-0
15 - 8
7-0

64
65
66
67
68
69 - 70
71
72
73
74
75 - 127
128 - 159
160 - 255

Description

Used

Fixed/Variable

Multiword DMA Transfer Mode Active
Multiword DMA Transfer Modes Supported
Reserved
Advanced PIO Transfer Mode Supported
Minimum Multiword DMA Transfer Cycle Time Per Word (ns)
Manufacturer’s Recommended Multiword DMA Transfer Cycle
Time (ns)
Minimum PIO Transfer Cycle Time without Flow Control
Minimum PIO Transfer Cycle Time with IORDY Flow Control
Reserved (for advanced PIO support)
Typical time (µs) for release when processing an overlapped
command
Typical time (µs) for release after receiving the service command
Major Revision Number (0000h or FFFFh Device does not
report version.
Minor Version Number (0000h or FFFFh Device does not report
version.
Reserved
Vendor Unique
Reserved

Mandatory

Variable
Fixed

Mandatory
Mandatory
Optional

Fixed
Fixed
Fixed

Optional
Optional
No
Optional

Fixed
Fixed

Optional

Fixed

Optional

Fixed

Optional

Fixed

Fixed

No
No
No

“Optional” Identify Drive words, which are not supported, shall be set to zero.
The ATAPI Identify Device command shall not delay the transfer of the Identify Drive data by more than 200 ms after
receipt of the command.

7.1.7.1 General Configuration Word (0)
Table 20 - Identify Drive Data - General Configuration (Word 0)
Bit
Byte
0
1

7/15

6/14

5/13

Removable
CMD DRQ Type
Protocol Type
Reserved

4/12

3/11

2/10

Reserved

CMD Packet Size

This field indicates the protocol in use by the device.
0Xb = ATA
10b = ATAPI
11b = Reserved

Bit 13

This is reserved for future enhancement

Bits 12-8 Device Type

Bit 7

Removable

working draft ATAPI

0/8

Device Type

Bits 15-14 Protocol Type

Reserved

1/9

This field indicates the device type.
The peripheral types are described in "Table 40 - Peripheral Device Types" on
page 94.
Indicates that the device has removable media.

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Bits 6-5

CMD DRQ Type

CD-ROM ATA (Task File) Commands
ATA (Task File) Command Implementation Requirements
This field indicates the command packet DRQ type used by this device.
00b = Microprocessor DRQ:
ATAPI devices reporting Microprocessor DRQ assertion shall assert DRQ
within 3ms of receiving the A0h ATAPI Packet Command.
Implementer’s Note: Devices reporting Microprocessor DRQ require the device driver to poll for up to 3ms or accept the granularity of an available timer tick. These issues may result in undesirable system delays when used with
multi-threaded OS drivers.
01b = Interrupt DRQ:
ATAPI devices reporting Interrupt DRQ assertion shall assert INTRQ in
conjunction with the assertion of the command packet DRQ. These devices
shall assert DRQ within 10ms of receiving the A0h ATAPI Packet Command.
10b = Accelerated DRQ:
ATAPI devices reporting Accelerated DRQ assertion shall assert DRQ within
50us of receiving the A0h ATAPI Packet Command.
11b = Reserved for future use.

Bits 4-2

Reserved

This field is unique for each protocol and is reserved for future use.

Bits 1-0

Command Packet Size

This field indicates the size of the command packets used by this device.
00b = 12 bytes (ALL CD-ROM)
01b = 16 bytes (Reserved for SAM Compliant Devices)
1Xb = Reserved for future use.

7.1.7.2 Serial Number (Words 10 - 19)
This optional field shall contain the drive’s serial number formatted as left-justified ASCII, padded with spaces (20h). If
the field is not supported then it shall be filled with spaces.

7.1.7.3 Firmware Revision (Words 23-26)
The contents of this field are vendor-specific, left-justified, and padded with spaces.

7.1.7.4 Model Number (Words 27 - 46)
The contents of this field are vendor-specific, left-justified, and padded with spaces.

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ATAPI CD-ROM Specification
CD-ROM ATA (Task File) Commands
7.1.7.5 Capabilities Word (Word 49)
Table 21 - Identify Drive Data - Capabilities Word (49)
Bit
Byte
0
1

7/15

Reserved
for Interleaved
DMA Supported

6/14

5/13

Reserved
for Proxy
Interrupt
Supported

Overlap
Operation
Supported
(Optional)

4/12

3/11

Vendor Unique
Reserved
IORDY
Supported
(Optional)

2/10

1/9

0/8

IORDY
can be disabled
(Optional)

LBA Supported
(Mandatory)

DMA Supported
(Optional)

Bit 8

DMA Supported

This bit indicates that the Device supports the DMA mode of data transfer.

Bit 9

LBA Supported

Indicates that the Device supports the LBA form of addressing. The ATAPI
Devices shall set this bit to one.

Bit 10

IORDY can be disabled

Is used to indicate a device’s ability to enable or disable the use of IORDY. If
this bit is set to one, then the device supports the disabling of IORDY.

Bit 11

IORDY Supported

This is used to help determine whether a device supports IORDY. If this bit is
set to one, then the device supports IORDY operation. If this bit is zero then
the device may support IORDY (this ensures backward compatibility.)

Bit 13

Overlap Operation Supported This device supports overlapped operations. Both the Release and Service protocol must be supported to report that the Device supports Overlap Operation.

Bit 14

Reserved for Proxy Interrupt

Bit 15

Reserved for Interleaved DMA This device will release BSY after transferring DMA data when DMA is used
for an overlapped command This bit is currently reserved for an interleaved
DMA capability that may be defined in the future.

This device supports a shared interrupt technique. This bit is currently reserved for the Proxy Interrupt technique that may be defined in the future.

7.1.7.6 PIO Data Transfer Cycle Timing (Word 51)
The PIO transfer timing for each ATA device falls into categories which have unique parametric timing specifications. To
determine the proper device timing category, compare the contents of this field with the Cycle Time specified in Figure 6
of the ATA document in Appendix B. The value returned in Bits 15-8 shall fall into one of the categories specified, and if
it does not, then Mode 0 shall be used to serve as the default timing.

7.1.7.7 DMA Data Transfer Cycle Timing (Word 52)
The DMA transfer timing for each ATA device falls into categories which have unique parametric timing specifications.
To determine the proper device timing category, compare the contents of this field with the Cycle Time specified in Figures 8 and 9 of the ATA document in Appendix B. The value returned in Bits 15-8 shall fall into one of the categories
specified, and if it does not, then Mode 0 shall be used to serve as the default timing.

7.1.7.8 Field Validity (Word 53)
Bit 0

When = 1, this bit guarantees that the fields contained in words 54-58 are valid.

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Bit 1

CD-ROM ATA (Task File) Commands
ATA (Task File) Command Implementation Requirements

When = 1, this bit guarantees that the fields contained in words 64-70 are valid.

7.1.7.9 Single Word DMA Transfer (Word 62)
The low order byte identifies by bit all of the modes which are supported, e.g., if Mode 0 is supported, bit 0 is set. The
high order byte contains a single bit set to indicate which mode is active, e.g., if Word 0 is active, bit8 is set.

7.1.7.10 Multi Word DMA Transfer (Word 63)
The low order byte identifies by bit all of the modes which are supported, e.g., if Mode 0 is supported, bit 0 is set. The
high order byte contains a single bit set to indicate which mode is active, e.g., if Word 0 is active, bit8 is set.

7.1.7.11 Enhanced PIO Mode (Word 64)
Bits 7 through 0 of the word 64 of the Identify Drive parameter information is defined as the Advanced PIO Data Transfer Supported Field. This field is bit significant. Any number of bits may be set in this field by the device to indicate
which Advanced PIO Modes that it is capable of supporting. Of these bits, bits 7 through 1 are reserved for future advanced PIO modes. Bit 0, if set, indicates that the device supports PIO Mode 3.

7.1.7.12 Minimum Multi-word DMA Transfer Cycle Time per Word (Word 65)
Word 65 of the parameter information of the IDENTIFY DRIVE command is defined as the Minimum Multi-word
DMA Transfer Cycle Time Per Word. This field defines, in nanoseconds, the minimum cycle time that the device can
support when performing Multi-word DMA transfers on a per word basis.
Any device which supports Multi-word DMA Mode 1 or above shall support this field, and the value in word 65 shall
not be less than 150.
If the device does not support this field, the device shall return a value of zero in this field.

7.1.7.13 Manufacturer’s Recommended Multi-word DMA Transfer Cycle Time (Word 66)
Word 66 of the parameter information of the IDENTIFY DRIVE command is defined as the Manufacturer’s Recommended Multi-word DMA Transfer Cycle Time. This field defines, in nanoseconds, the minimum cycle time per word
during a single sector host transfer while performing a multiple sector READ DMA or WRITE DMA commands over all
locations on the media under nominal conditions. A cycle time less than this value may cause DMARQ to be deasserted
at a rate which may reduce throughput without data corruption.
Any device which supports Multi-word DMA Mode 1 or above shall support this field, and the value in word 66 shall
not be less than the value in word 65.
If the device does not support this field, the device shall return a value of zero in this field.

7.1.7.14 Minimum PIO Transfer Cycle Time Without Flow Control (Word 67)
Word 67 of the parameter information of the IDENTIFY DRIVE command is defined as the Minimum PIO Transfer
Without FLow Control Cycle Time. This field defines, in nanoseconds, the minimum cycle time that, if used by the host,
the device guarantees data integrity during the transfer without utilization of flow control.
Any device which supports PIO Mode 3 or above shall support this field, and the value in word 67 shall not be less than
180.

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ATAPI CD-ROM Specification
CD-ROM ATA (Task File) Commands

If the device does not support this field, the device shall return a value of zero in this field.

7.1.7.15 Minimum PIO Transfer Cycle Time with IORDY Flow Control (Word 68)
Word 68 of the parameter information of the IDENTIFY DRIVE command is defined as the Minimum PIO Transfer
With IORDY Flow Control Cycle Time. This field defines, in nanoseconds, the minimum cycle time that the device can
support while performing data transfers while utilizing IORDY flow control.
Any device which supports PIO Mode 3 or above shall support this field, and the value in word 68 shall not be less than
180. If the device does not support this field, the device shall return a value of zero in this field.

7.1.7.16 Typical Time for the Release After Command Received (Word 71)
Devices reporting support for overlapped operations shall report the typical (3sigma) time in microseconds that the device takes to release the bus after receipt of any A0 packet command. Note that for performance reasons a device may
choose not to release the bus. Host systems may assume that the device has chosen not to release the bus after waiting
three times the typical time reported in this word (See "5.17.1 Release" on page 40).

7.1.7.17 Typical Time for the Clearing of Busy After SERVICE Command (Word 72)
Devices reporting support for overlapped operations shall report the typical (3 sigma) time in microseconds that the device takes to clear Busy after receipt of a Service command (See "5.17.1 Release" on page 40).

7.1.7.18 Major Version Number (Word 73)
If not 0000h or FFFFh, the device claims compliance with the major version(s) as indicated by bits 1 through 2 being
equal to one (ATAPI 1.x and 2.x). Values other than 0000h and FFFFh are bit significant.

7.1.7.19 Minor Version Number (Word 74)
If an implementor claims that the revision of the specification they used to guide their implementation does not need to
be reported or if the implementation was based upon a specification prior to this revision of the standard, word 73 shall
be 0000h or FFFFh. Reported value for this compliance with this specification shall be 9h.

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CD-ROM ATA (Task File) Commands
ATA (Task File) Command Implementation Requirements

7.1.8 Service
The Service command is used to restore the task file of a device which has released the ATA bus while processing an
overlapped command. Unlike all other commands, a device processing an overlapped command which has its service bit
set shall not abort the command in progress. Upon completion of the Service command the device’s task file shall reflect
the correct status of the overlapped command.
Upon receipt of the Service command the device shall clear the SERVICE bit before it de-asserts BSY (See "7.1.8 Service" on page 68).
Completion of the Service Command is different than all other commands. It occurs when the state of the “Task File”
registers has been restored to the state they would be in if no release had occurred. In this case, the Busy bit shall be
cleared.

7.1.9 Set Features
The Set Features command is used to set some interface timing and protocol modes. These modes are set at Post by many
BIOSes. The contents of the ATAPI Features Register indicates the function to be performed.

Table 22 - Contents of the Feature Register for Set Features Command
Bit
Byte
0

7

6

5

4

Set (1)/
Clear (0)
Feature

3

2

1

0

Feature Number

Table 23 - Set Feature Register Definitions
Register
Contents

Set Feature Commands

Support

01h

Enable 8-bit data transfers

No

02h

Enable write cache

03h

Set transfer mode based on value in sector count register

33h

Disable retry

No

44h

Vendor unique length of ECC on read long/write long commands

No

No
Mandatory

54h

Set cache segments to sector count register value

5Dh

Enable Interrupt for Release after the receipt of an Overlapped Command

Mandatory1

5Eh

Enable Interrupt after the completion of A2h Service Command

Mandatory2

55h

Disable read look-ahead feature

66h

Disable reverting to power on defaults

77h

Disable ECC

No

81h

Disable 8-bit data transfers

No

82h

Disable write cache

No

88h

Enable ECC

No

99h

Enable retries

No

AAh

Enable read look-ahead feature

No

ABh

Set maximum prefetch using sector count register value

No

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ATAPI CD-ROM Specification
CD-ROM ATA (Task File) Commands
Table 23 - Set Feature Register Definitions (Continued)
Register
Contents

Set Feature Commands

Support

BBh

4 bytes of ECC apply on read long/write long commands

CCh

Enable reverting to power on defaults

Mandatory1

DDh

Disable Interrupt for Release after the receipt of an Overlapped Command

Mandatory1

DEh

Disable Interrupt after the Completion of A2h Service Command

Mandatory2

1.
2.

No

Mandatory if the device reports more than 50 µs in word 71 of the identify drive data and supports Overlap.
Mandatory if the device reports more than 50 µs in word 72 of the identify drive data and supports Overlap.

If the value in the register is not supported or is invalid, the drive posts an Aborted Command error.
At power on, or after a hardware reset, the default mode is the same as that represented by values greater than 80h.

7.1.9.1 Set Transfer Mode (03h)
A host can choose the transfer mechanism by Set Transfer Mode and specifying a value in the Sector Count Register.
The upper 5 bits define the type of transfer and the low order 3 bits encode the mode value. Since both PIO and DMA
settings can be active simultaneously, the Device shall maintain independent transfer mode settings for both PIO and
DMA.

Table 24 - Feature Number Description for Set Feature Command
Feature Number
03h

Default Setting
Data Transfer Mode. Mode contained in Sector Count Register.
Value in Sector
Count Register
Definition
00000 00x
PIO Default Transfer Mode
00001 xxx
PIO Flow Control Transfer mode x
00010 xxx
Single Word DMA mode x
00100 xxx
Multi-word DMA
00011 xxx
Reserved (For Pseudo DMA mode)

PIO & DMA Mode 0

If a device which supports this specification receives a Set Feature command with a Set Transfer Mode parameter and a
Sector count Register value of 00000 000, it shall set its default PIO transfer mode.
If a device which supports this specification receives a Set Feature command with a Set Transfer Mode parameter and a
Sector Count Register value of 00000 001 and the device supports disabling of IORDY, then the device shall set its default PIO transfer mode and disable IORDY.

7.1.9.2 Enable Interrupt for Release after receipt of Command Packet (5Dh)
A setting of 5Dh will cause the device to issue an interrupt when the device has released the bus to the host.

7.1.9.3 Enable Interrupt After Completion of Service Command (5Eh)
A setting of 5Eh will cause the device to issue an interrupt when the device has finished processing the Service command
(clearing Busy).

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CD-ROM ATA (Task File) Commands
ATA (Task File) Command Implementation Requirements

7.1.9.4 Disable Reverting to Power On Defaults (66h)
A setting of 66h allows settings of greater than 80h which may have been modified since power on to remain at the same
setting after a software reset. At power on, or after a hardware reset, the default mode is the same as that represented by
values greater than 80h.

7.1.9.5 Enable Reverting to Power On Defaults (CCh)
A setting of CCh will cause the Device to revert back to the default for settings of greater than 80h, which may have been
modified since power on, after a software reset.

7.1.9.6 Disable Interrupt for Release after receipt of Command Packet (DDh)
A setting of DDh will cause the device not to issue an interrupt when the device has released the bus to the host.

7.1.9.7 Disable Interrupt After Completion of Service Command (DEh)
A setting DEh will cause the device not to issue an interrupt when the device has finished processing the Service command (clearing Busy).

7.1.10 Sleep
This command is the only way to cause the drive to enter Sleep Mode. The drive is spun down, and when it is stopped,
BSY is cleared, an interrupt is generated, and the interface becomes inactive.
The only way to recover from Sleep mode is with a software reset or a hardware reset.
NOTE: The use of hardware reset to recover from Sleep mode may be incompatible with continued operation of the host system.

A drive shall not power on in Sleep Mode nor remain in Sleep Mode following a reset sequence. If the drive is already
spun down, the spin down sequence is not executed.

7.1.11 Standby Immediate
This command causes the drive to enter the Standby Mode. The drive may return the interrupt before the transition to
Standby Mode is completed.
If the drive has already spun down, the spin down sequence is not executed.
For Standby immediate the drive may return the interrupt before the transition to Standby Mode is completed.
For Sleep, the drive may return the interrupt before the transition to Sleep Mode is completed.

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CD-ROM Model

8.0 CD-ROM Model
CD-ROM devices permit reading data from a rotating media. Writing the media is not currently supported, but will be in
the future (CD-WO and CD-MO). Data transfer can begin with any of the consecutively numbered logical blocks. Data
on CD-ROM devices is addressed the same as for (magnetic) direct-access devices. Some CD-ROM devices support a
separate information stream (e.g. audio and/or video but referred to as audio in this Section) transmitted via a connection
other than the AT Bus. This specification defines commands for controlling these other information streams for CDROM devices.
CD-ROM drives are designed to work with any disc that meets IEC. Many new drives read CD-ROM data discs, digital
audio discs, and audio-combined discs (i.e. some tracks are audio, some tracks are data).

8.1 New Capabilities Since the SCSI-2 Standardization
Unfortunately, the introduction of Photo CDs (with multiple sessions), CD-ROM XA Format (two different format
modes), and CD-I has occurred after the standardization effort. In addition, the SCSI standard did not provide a method
to return the CD-DA data. As is characteristic with “new” functionality, each vendor has devised their own solutions.
This ATAPI Proposal has taken the “Common Command Set (CCS)” approach to the problem and created a minimal
mandatory command set that includes capabilities that are currently addressed by the DRAFT SCSI-3 Multi-media Command standard (MMC).

8.2 CD-ROM Media Organization
The formats written on the CD-ROM and CD-DA (Digital Audio) media require special interfacing considerations.
NOTE This subsection contains a number of terms that have special meanings peculiar to CD-ROM technology or that may be unfamiliar to many
readers of this Specification. The glossary defines these terms.

Discs may contain either audio, data or a mixture of the two. "Table 25 - Example Mixed Mode CD-ROM Disc Layout"
on page 72 gives an example of an audio-combined disc to illustrate the relationship between the logical block addresses
reported and the MSF address encoded on the media.
NOTE: The term “frame” is used in two different ways in the CD-ROM media standard. The intended meaning can only be determined from the context. Whenever possible, this description replaces the larger data unit with the more familiar term sector. The primary exception to this policy is the use
of frame when referring to the MSF address. In the MSF context, one frame (F field unit) equals one sector. On a typical two channel CD-DA media,
each frame (F field unit) is played in 1/75th of a second.

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CD-ROM Media Organization

Table 25 - Example Mixed Mode CD-ROM Disc Layout
Block Description
Lead-in area3
3

Logical
Address
(Decimal)

Absolute
MSF
Address1

Track and
Index

---

---

0/-

---

Audio

---

Mode
Audio or
Data

CD-ROM
Data
Mode2

00/00/00

1/0

Pause

Data

Null

4

00/02/005

1/1

Info

Data

L-EC

4

6000

01/16/005

2/1

Info

Data

L-EC

7500

01/2A/00

2/2

Info

Data

L-EC

Post-gap

9000

02/02/00

2/3

Pause

Data

Null

Pause-silence

9150

02/04/00

3/0

Pause

Audio

---

02/04/007

3/1

Info

Audio

---

02/22/00

3/2

Info

Audio

---

4/1

Info

Audio

---

Pre-gap

1st track data
2nd track data

3rd track audio

---

Sector is
Info or is
Pause

0000

6

9300
1400

6

4th track audio

21975

04/35/007

Pre-gap part 1

30000

06/28/00

5/0

Pause

Audio

---

Pre-gap part 2

30075

06/29/00

5/0

Pause

Data

Null

5th track data

30225

06/2B/00

5/1

Info

Data

L-EC

8

Last information

263999

3A/27/4A

5/1

Info

Data

L-EC

Post-gap

---

3A/28/00

5/2

Pause

Data

Null

58/42/0010

AA/11

Pause

Audio

---

Lead-out track

9

264000

1.
2.

Absolute MSF address repeated in the header field of data blocks.
The CD-ROM data mode is stored in the header of data tracks. This indicates that the block is
part of a data pre-gap or post-gap (null), that this is a data block using the auxiliary field for LEC symbols (ECC - CD-ROM data mode one), or that this is a data block using the auxiliary
field for user data (CD-ROM data mode two).
3. Table of contents information is stored in the sub-channel of lead-in area. The lead-in area is
coded as track zero. Track zero and the initial 150 sector pre-gap (or audio pause) are not accessible with logical addressing.
4. Exact value returned by READ TOC command.
5. Value stored in table of contents with zero tolerance.
6. Value returned by READ TOC command plus or minus 75 blocks.
7. Value stored in table of contents plus or minus 75 sectors.
8. Minimum value returned by READ CD-ROM CAPACITY; exact value depends on encoding of
this track and the lead out track and whether this is derived from the TOC data.
9. Value returned by READ TOC command; exact, if lead-out track is encoded as data, or plus or
minus 75 blocks if encoded as audio.
10. Value stored in table of contents; exact, if lead-out track is coded as data, or plus or minus 75
blocks if coded as audio.
11. Lead-out track number is defined as 0AAh.

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CD-ROM Model
The physical format defined by the CD-ROM media standards provides 2352 bytes per sector. For usual computer data
applications, 2048 bytes are used for user data, 12 bytes for a synchronization field, 4 bytes for a sector address tag field
and 288 bytes - the auxiliary field - for L-EC (CD-ROM data mode 1). In less critical applications, the auxiliary field may
also be used for user data (CD-ROM data Mode 2 / Form 2).

Yellow Book
Mode 1

Sync Header
12

Data

4

2048

EDC

0

4

8

ECC (P&Q)
276

Auxiliary Field (288)

Yellow Book
Mode 2

Sync Header
12

Data
2336

4

Sync Header
XA
Mode 2 Form 1

12

4

Data

8
SubHeader

4

2048

12

4

Data

8
SubHeader

SmallFrame(1)
CD Digital Audio

276

Auxiliary Field (280)

Sync Header
XA
Mode 2 Form 2

EDC ECC (P&Q)

2324

Spare
4
Note that the Spare data is
normally returned with the
user data
SmallFrame(98)

6x4

SubChannel

Figure 11 - CD-ROM Sector Formats
A CD-ROM physical sector size is 2048, 2052, 2056, 2324, 2332, 2336, 2340 or 2352 bytes per sector. These values correspond to the user data plus various configurations of header, subheader and EDC/ECC.
This same area of the CD-ROM or CD audio media may store 1/75th of a second of two channel audio information formatted according to the CD-DA specification. (These audio channels are usually the left and right components of a stereo pair.) An audio only density code value can be used to declare an area of the media to be invalid for data operations.
For data and mixed mode media (those conforming to ISO/IEC 10149), logical block address ZERO shall be assigned to
the block at MSF address 00/02/00. For audio media (those conforming only to IEC 908), logical block address ZERO
shall be assigned to the actual starting address of track 1. This may be approximated by using the starting address of
track 1 contained in the table of contents (TOC) or by assigning logical block address ZERO to the block at MSF address 00/02/00.
Logical addressing of CD-ROM information may use any logical block length. When the specified logical block length
is an exact divisor or integral multiple of the selected number of bytes per CD-ROM sector, the device shall map (one to
one) the bytes transferred from CD-ROM sectors to the bytes of logical blocks. For instance, if 2048 bytes are transferred
from each CD-ROM sector (specified by the CD-ROM density code value), and the logical block length is 512 bytes,
then each CD-ROM sector shall map to exactly four logical blocks. This Specification does not define the mapping of
logical block lengths which do not evenly divide or are not exact multiples of the selected number of bytes per CD-ROM
sector.

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CD-ROM Media Organization

A track may be viewed as a partition of the CD-ROM address space. A CD-ROM media contains from one to ninetynine tracks. All information sectors of a track are required to be of the same type (audio or data) and mode. Each change
in the type of information on the disc requires a change in track number. A disc containing both audio and data would
have at least two tracks, one for audio and one for data.
The tracks of a CD media are numbered consecutively with values between 1 and 99. However, the first information track
may have a number greater than 1. Tracks have a minimum length of 300 sectors including any transition area that is part
of a track.
The CD-ROM media standards require transition areas between tracks encoded with different types of information. In
addition, transition areas may be used at the beginning or end of any track. For audio tracks the transition areas are
called pause areas. For data tracks, transition areas are called pre-gap and post-gap areas. See "Table 25 - Example
Mixed Mode CD-ROM Disc Layout" on page 72 for an example. The IEC 908 and ISO/IEC 10149 standards specify
minimum time durations for these areas. Maximum time durations are not specified.
Transition areas are formatted and the logical address continues to increment through transition areas. Some media (i.e.
discs with only one track) may not have transition areas. The means to determine the location of the transition areas is
vendor or application-specific and is addressed by other standards (e.g. ISO 9660).
CD-ROM is a unique device in the respect that some logical blocks on a disc may not be accessible by all commands.
SEEK commands may be issued to any logical block address within the reported capacity of the disc. READ commands
cannot be issued to logical blocks that occur in some transition areas, or to logical blocks within an audio track. PLAY
commands cannot be issued to logical blocks within a data track.
CD-ROM media have lead-in and lead-out areas. These areas are outside of the user-accessible area as reported in the
READ CD-ROM CAPACITY data. The lead-in area of the media is designated track zero. The lead-out area is designated track 0AAh. The sub-channel Q in the lead-in track contains a table of contents (TOC) of the disc.
NOTE: The READ CD-ROM CAPACITY command returns the logical block address of the last block prior to the lead-out area. This location may be in
a transition area and therefore not a valid address for read operations.

The table of contents gives the absolute MSF location of the first information sector of each track. Control information
(audio/data, method of audio encoding, etc.) for each track is also given in the TOC. However, the TOC does not distinguish between the different modes of data tracks (i.e. CD-ROM Data Mode 1 vs. CD-ROM Data Mode 2).
The MSF locations of the beginning of data tracks in the TOC are required to be accurate; however, the TOC values for
audio tracks have a tolerance of plus or minus 75 sectors. Information from the TOC can be used to reply to a READ
CD-ROM CAPACITY command. When this is done, the drive implementor shall consider the possible tolerances and return a value that allows access to all information sectors.
An index is a partition of a track. Pre-gap areas are encoded with an index value of zero. Pause areas at the beginning of
audio tracks are also encoded with an index value of zero. The first information sector of a track has an index value of
one. Consecutive values up to 99 are permitted. Index information is not contained in the TOC. Not all sectors are encoded with the index value in the Q-sub-channel data (the requirement is 9 out of 10). A sector without an index value is presumed to have the same index as the preceding sector.
Tracks and indexes are not defined to be any particular length, (except for a minimum track length of 300 sectors.) A CD
disc may be created with a single information track that has a single index; or with 99 information tracks, each with 99
indexes.
The sub-channel information which is part of each sector includes a track relative MSF location value giving the distance from the first information sector of the track. On the media, this value decreases during the pre-gap area (sectors
with index values of 0) and increases for the rest of the track. The data, returned by the READ SUB-CHANNEL command with MSF bit set to zero, converts this to a track relative logical block address (TRLBA). The TRLBA is continual-

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CD-ROM Model
ly increasing over the whole track, and pre-gap areas shall return negative values. When the MSF bit in the read subchannel command is set to one, the MSF track relative location value from the media is reported without change.
Note: The purpose of accessing MSF addresses less than 00M 02S 00F is to retrieve information, such as packet size,
from incrementally written discs. This information exists in the track descriptor block in the pre-gap area. Users can read
this information by scanning the area between 00M 01S 00F to 00M 02S 00F. While the media may contain multiple redundant copies of the pre-gap data, the device shall only return one copy. The drive may not be able to read 00M 00S
00F since there is no Sub-Q information before this frame. Refer to CD-ROM Orange book for additional details.

8.3 CD-ROM Physical Data Format
The physical format of CD-ROM and CD-DA media uses a smaller unit of synchronization than the more familiar magnetic or optical recording systems. The basic data stream synchronization unit is a small frame. This is not the same
large frame (sector) as referred to in the MSF unit. Each small frame consists of 588 bits. A sector on CD-ROM media
consists of 98 small frames.
A CD-ROM small frame consists of:
1.

1 synchronization pattern (24+3 bits)

2.

1 byte of sub-channel data (14+3 bits)

3.

24 bytes of data (24 x (14+3) bits)

4.

8 bytes of CIRC code (8 x (14+3) bits) Total: 588 bits.

Data, sub-channel and CIRC bytes are encoded with an 8-bit to 14-bit code; then three merging bits are added. The merging bits are chosen to provide minimum low-frequency signal content and optimize phase lock loop performance.

8.3.1 Frame Format for Audio
Each small frame of an audio track on a two-channel CD-DA or CD-ROM media consists of six digitized 16-bit samples
of each audio channel. These 24 bytes of data are combined with a synchronization pattern, CIRC bytes and a sub-channel byte to make a frame. Each frame takes approximately 136.05 µs to play. This gives a sampling rate of 44.1 kHz for
each channel. The sub-channel information creates the higher level sector grouping for audio tracks.

8.3.2 Sector Format for Data
The data bytes of 98 small frames comprise the physical unit of data referred to as a sector. (98 small frames times 24
bytes per small frame equals 2352 bytes of data per sector.)
A sector that contains CD-ROM Data Mode 1 data has the following format:
1.

12-byte synchronization field

2.

4-byte CD-ROM data header
Absolute M field
Absolute S field
Absolute F field
CD-ROM data mode field

3.

2048-byte user data field

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4.

4-byte error detection code

5.

8 bytes zero

6.

276-byte layered error correction code

CD-ROM Model
CD-ROM Physical Data Format

A sector that contains CD-ROM Data Mode 2 data has the following format:
1.

12-byte synchronization field

2.

4-byte CD-ROM data header
Absolute M field
Absolute S field
Absolute F field
CD-ROM data mode field

3.

2336-byte user data field (2048 bytes of mode 1 data plus 288 bytes of auxiliary data)

NOTE Many drives are capable of returning CD-ROM data mode one data in a CD-ROM data mode two format. This allows the user to investigate
the error detection and error correction codes. However data encoded as CD-ROM data mode two cannot be read as CD-ROM data mode one data.

8.3.3 Sub-channel Information Formats
The sub-channel byte of each frame is assigned one bit for each of the 8 sub-channels, designated P, Q, R, S, T, U, V, W.
Sub-channel P is a simple flag bit that may be used for audio muting control and track boundary determination.
Sub-channel Q has a higher level of structure. All the sub-channel Q bits of a sector define the sub-channel Q information
block. (For audio tracks, decoding the Q sub-channel is the only way to distinguish sector boundaries.)
The sub-channel Q block consists of 98 bits, one bit from each small frame in a sector. Three formats are defined for the
sub-channel Q information block. The first format provides location information and is defined as follows:
1.

2-bit sub-channel synchronization field

2.

4-bit ADR field (defines the format)

3.

4-bit control field (defines the type of information in this sector)

4.

8-bit track number

5.

8-bit index number

6.

24-bit track relative MSF address

7.

8 bits Reserved (0)

8.

24-bit Absolute MSF address

9.

16-bit CRC error detection code

This format is required to exist in at least nine out of ten consecutive sectors.

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CD-ROM Model
The second and third formats are optional. If used, they shall exist in at least one out of 100 consecutive sectors. They include the absolute frame byte of the MSF address to provide location information continuity.
The second format gives the catalogue number of the disc (UPC/EAN bar code number). This information is constant
over the whole media.
The third format gives the International Standard Recording Code (ISRC) for each track. The ISRC is defined in ISO
3901. This format is not present on lead-in or lead-out tracks and may change only after the track number changes.

8.4 CD Audio Error Reporting
PLAY AUDIO commands with the immediate bit set in the audio control mode return status as soon as the command has
been validated (which may involve a seek to the starting address). The playback operation continues and may complete
without notification to the Host Computer. Error termination of audio operations shall be reported to the Host Computer
by returning immediate CHECK CONDITION status to the next command (except for REQUEST SENSE and INQUIRY.) The deferred error sense data is used to indicate that the error is not due to the current command.
The status of the play operation may be determined by issuing a REQUEST SENSE command. The sense key is set to
NO SENSE and the audio status is reported in the additional sense code qualifier field.

8.5 CD-ROM Ready Condition/Not Ready Condition
The ready condition occurs after a cartridge is inserted and the drive has performed its initialization tasks. These may include reading the table of contents from the media. This “Ready” is different from and shall not be confused with the
ATA Ready Status. A check condition status will be returned for the not ready condition only for commands that require
or imply a disc access.
A not ready condition may occur for the following reasons:
1.

There is no cartridge inserted.

2.

The drive is unable to load or unload the cartridge.

3.

The drive is unable to recover the table of contents.

The drive shall spin up and make the disc ready for media accesses when a new disc is detected.
Any media access that occurs when the drive is not spinning shall spin the drive up and not generate an error.

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CD-ROM Model
CD-ROM Address Reporting Formats (MSF bit)

8.5.1 Packet Command Not Ready Status Utilization

Table 26 - Not Ready Error Reporting (by Command)
Command

Opcode

INQUIRY
LOAD / UNLOAD CD
MECHANISM STATUS
MODE SELECT(10)
MODE SENSE(10)
PAUSE/RESUME
PLAY AUDIO
PLAY AUDIO MSF
PLAY CD
PREVENT/ALLOW MEDIUM REMOVAL

12h
A6h
BDh
55h
5Ah
4Bh
45h
47h
BCh
1Eh

READ(10)
READ(12)
READ CD-ROM CAPACITY
READ CD
READ CD MSF
READ HEADER
READ SUB-CHANNEL
READ TOC
REQUEST SENSE
SCAN
SEEK
SET CD SPEED
STOP PLAY / SCAN
START STOP UNIT
TEST UNIT READY

28h
A8h
25h
BEh
B9h
44h
42h
43h
03h
BAh
2Bh
BBh
4Eh
1Bh
00h

May Return Not Ready Error
No
Yes
No
No
No
Yes
Yes
Yes
Yes
See Actions for Lock / Unlock / Eject
on page 136 for Actions allowed
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
No
Yes
Yes
Yes

8.6 CD-ROM Address Reporting Formats (MSF bit)
Several CD-ROM specific commands can return addresses either in logical or in MSF format. The READ HEADER,
READ SUB-CHANNEL and READ TABLE OF CONTENTS commands have this feature.

Table 27 - MSF Address Format
Bit
Byte
0
1
2
3

7

6

5

4

3

2

1

0

Reserved
M Field
S Field
F Field

An MSF bit of zero requests that the logical block address format be used for the CD-ROM absolute address field or for
the offset from the beginning of the current track expressed as a number of logical blocks in a CD-ROM track relative address field.

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CD-ROM Model

An MSF bit of one requests that the MSF format be used for these fields. In certain transition areas, the relative MSF addresses are decreasing positive values. The absolute MSF addresses are always increasing positive values.The M, S, and
F fields are expressed as binary numbers. Sensing Support for CD-Audio Commands
If any commands related to audio operations are implemented, then all the AUDIO commands shall be implemented. To
allow a method for the Host Computer to determine if audio operations are supported, an ATAPI CD-ROM Drive responding to a PLAY AUDIO command which has a transfer length of zero, with CHECK CONDITION status, and setting the sense key to ILLEGAL REQUEST does not support audio operations.

8.7 Error Reporting
If any of the following conditions occur during the execution of a command, the ATAPI CD-ROM Drive shall return
CHECK CONDITION status. The appropriate sense key and additional sense code shall be set. The following list illustrates some error conditions and the applicable sense keys. The list does not provide an exhaustive enumeration of all
conditions that may cause the CHECK CONDITION status.

Table 28 - Error Conditions and Sense Keys
Condition
Invalid logical block address
Unsupported option requested
Attempt to read a blank block
Attempt to play a data block as audio
ATAPI CD-ROM Drive reset or medium change since last command
Self diagnostic failed
Unrecovered read error
Recovered read error
Overrun or other error that might be resolved by repeating the command

Sense Key
ILLEGAL REQUEST
ILLEGAL REQUEST
ILLEGAL REQUEST
ILLEGAL REQUEST
UNIT ATTENTION
HARDWARE ERROR
MEDIUM ERROR / HARDWARE ERROR
RECOVERED ERROR
ABORTED COMMAND

In the case of an invalid logical block address, the sense data information field shall be set to the logical block address of
the first invalid address.
In the case of an attempt to read a blank or previously unwritten block, the sense data information field shall be set to the
logical block address of the first blank block encountered. The data read up to that block shall be transferred.
There are other special error situations for CD-ROM devices. In the following cases the sense key shall be set to ILLEGIAL REQUEST and the additional sense code set to END OF USER AREA ENCOUNTERED ON THIS TRACK:
1.

a post-gap area is encountered (i.e. a block with CD-ROM Data Mode 0);

2.

a pre-gap area is encountered (i.e. a block with index equal to 0);

3.

The information type (Data Mode vs. Audio etc.) changes.

When not performing audio playback, if the logical block address requested is not within a data track, the command shall
be terminated with CHECK CONDITION status. The sense key shall be set to ILLEGIAL REQUEST and the additional
sense code set to ILLEGAL MODE FOR THIS TRACK. This applies to audio-combined and audio media.

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Error Reporting

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ATAPI CD-ROM Specification
Changer Model

9.0 Changer Model
A changer device will perform exactly like a single ATAPI CD-ROM drive. However it will support two (2) new commands, MECHANISM STATUS (BDh) and LOAD/UNLOAD CD (A6h).
A changer device provides a storage area for more than one CD Disc. This storage area contains multiple areas called
slots. Each slot can contain just one Disc. Once a Disc has been placed in to a given slot, it becomes locked in that position. This specification provides no capability to move a Disc from one slot to another. Thus when a Disc has been moved
from a given slot into the playing position, it can only be moved back into the slot that it came from. This shall be followed even if power is lost while a Disc is in the playing position or while it was being moved.
There are two basic types of changer mechanisms, one that has individually addressable eject and load capability and another that uses a cartridge to hold the discs. In the former, individual disc can be changed, while in the later all the stored
discs must be changed at one time.
Any time a Disc/Cartridge is removed or installed from the changer, the device shall generate an Unit Attention Condition. After the host detects the unit attention on a known changer device, the host may issue a MECHANISM STATUS
Command. This will provide the host with information on what disc is present or was changed.

Changer Mechanism
using Individual Disc
Load and Unload
Load/Unload
Command
Eject Command

Changer Mechanism
using Cartridges

CD-ROM Mechanism
Eject Command

Load/Unload
Command

CD-ROM Mechanism

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Changer Model
Initialization

9.1 Initialization
The Changer shall perform it’s initialization routine at power on or receipt of a hardware reset from the host.
“Initializing Changer” is a process that refers to gathering the information that is necessary to respond to the MECHANISM STATUS Command. If a changer is in the process of Initializing when it receives a MECHANISM STATUS Command, it will respond immediately and provide no slot table information (Only the Header).

POR

No Cartridge
Present

Cartridge
Loaded

EJECT Cartridge
Command
Idle but no Disc
Drive will be NOT READY
but the Changer State is
“Ready”
Wait for Disc
Change or
A Load
Command
“Unit Attention”
If a Disc is added
or removed

Reset
(State is Initializing)

Power On
Initialization

Reset and
Load Disc 0

Disc 0
is present

Disc 0
is present

Disc 0 is
not present

Generate
an “Unit Attention”
for the Ready to
Not Ready

Idle
(State is Ready)

EJECT
Single Disc
Command

Read TOC &
Make Disc
Ready to use

“Unit Attention”
If a Disc is added
or removed

Unload Complete
Load
Compete

Move current
Disc from
Playing
Position to
Storage

UNLOAD
Command

Unload
(State is Unload In Progress)

LOAD
Command

Move Specified
Slot into the
Play Position
Load
(State is Load In
rogress)

LOAD
Command

Figure 12 - Changer State Diagram

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Changer Model
9.2 Changer Addressing
Several Changer specific commands use addresses called “Slots”.
If any commands related to Changer operations are implemented, then all the Changer commands shall be implemented.
To determine if an ATAPI Drive is a changer type device, the Loading Mechanism Type field in the Capabilities page
will contain one of the two changer type code (See "10.8.6.4 CD-ROM Capabilities and Mechanical Status Page" on
page 118) for individual disc or cartridge implementations.

9.3 Automatic Load and Unload Operations
After initialization is complete the changer shall have Disc 0 loaded into the play position. This enables drivers which are
not changer aware to work with a changer device as if it were a normal single Disc ATAPI CD-ROM device. This also insures compatibility with Bootable CD. In support of this goal the changer shall also load and unload (Eject) default Disc
0 if the changer supports loading and unloading (Ejecting) individual Discs unless otherwise commanded by the use of
one of the changer specific Load/Unload command.
When a LOAD Command is received and a Disc is present in the Playing position, it shall be unloaded automatically before the specified Load operation is performed.

9.4 Delayed Disc load operation
CD Changer Devices may either move a disc into the playing position immediately upon receipt of a LOAD command,
or delay the loading of the disc until a media access command is received. It is recommended that the device not load
discs into the playing position until data from a disc that is not cached is requested from the host.
Note that Host Drivers should expect to encounter load mechanism delays on media accesses in addition to the spin up
and seek delays normally introduced with these commands.
If the device supports delayed loading and the selected disc is not in the play position, then the following commands
shall move the selected disc into the play position When data that has not been cached has been requested by the host:

Table 29 - Commands that may cause delayed loads to occur
Command
Play Audio (10)
Play Audio MSF
Play CD
Read (10)
Read (12)
Read CD
Read CD MSF
Read CD-ROM Capacity
Read Header
Read Sub-Channel
Read TOC
Scan

If the device supports delayed loading and the selected disc is not in the play position, then the following commands shall
load the selected disc into the play position before execution of the command:

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Changer Model
Prevent / Allow processing

Table 30 - Commands that will cause delayed loads to occur
Command
Seek
Start/Stop Unit (LoEj=1)

If the device supports delayed loading and the selected disc is not in the play position, then the following commands shall
not move the selected disc into the play position:

Table 31 - Commands that should not cause delayed loads to occur
Command
Stop Play / Scan
Start/Stop Unit (LoEj=0)
Test Unit Ready
Inquiry
Mechanism Status
Mode Select
Mode Sense
Prevent / Allow Medium Removal
Request Sense
Set CD Speed

9.5 Prevent / Allow processing
There are two techniques for Prevent / Allow, either all the discs shall be prevented from being ejected by the user or
each disc individually shall be prevented. If the device reports support for Software Slot Selection, then each slot shall
be individually controlled by the Prevent / Allow command. Note that changer devices that use a Cartridge and not individually controlled slots should not report the Software Slot Selection capability.

9.6 Error Reporting
If any of the following conditions occur during the execution of a command, the ATAPI Changer shall return CHECK
CONDITION status. The appropriate sense key and additional sense code shall be set. The following list illustrates
some error conditions and the applicable sense keys. The list does not provide an exhaustive enumeration of all conditions that may cause the CHECK CONDITION status.

Table 32 - Error Conditions and Sense Keys for Changer Mechanisms
Condition
Invalid Slot Number
Unsupported option requested
Load or Unload to invalid slot or no Disc in source location
ATAPI CD-ROM Drive reset or medium change since last command
Self diagnostic failed

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Sense Key
ILLEGAL REQUEST
ILLEGAL REQUEST
ILLEGAL REQUEST
UNIT ATTENTION
HARDWARE ERROR

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ATAPI CD-ROM Specification
Changer Model

In the case of an invalid Slot number, the sense data information field shall be set to the Slot number of the first invalid
address.
Attempts to eject a Disc if the changer type is cartridge and there is a Disc in the playing position shall be rejected with
a Sense Key 05, (ILLEGIAL REQUEST) Sense Code 01 (MECHANICAL POSITIONING OR CHANGER ERROR).

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Error Reporting

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ATAPI CD-ROM Specification
CD-ROM Packet Commands

10.0 CD-ROM Packet Commands
10.1 Packet Command Implementation Requirements
The first byte of all ATAPI CD-ROM Drive Command Packets shall contain an operation code as defined in this Specification. ATAPI CD-ROM Drives shall implement all commands with mandatory operation codes.

10.1.1 Reserved
Reserved bits, fields, bytes, and code values are set aside for future standardization. Their use and interpretation may be
specified by future extensions to this or other standards. A reserved bit, field, or byte shall be set to zero, or in accordance
with a future extension to this standard. The recipient shall not check reserved fields.

10.1.2 Operation Code Types
The operation code types are defined in Table 33 - below.

Table 33 - Operation Code Types
Operation
Code Type
M
O
V
R

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Description
Mandatory - Commands so designated shall be implemented in order to meet the minimum requirement of this Specification.
Optional - Commands so designated, if implemented, shall be implemented as defined in this Specification.
Vendor-specific - Operation codes so designated are available for vendor defined commands. See the
vendor specifications where compatibility is desired.
Reserved - Operation codes so designated shall not be used. They are reserved for future extensions to
this Specification.

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CD-ROM Packet Commands
ATAPI Command Packet Description

10.2 ATAPI Command Packet Description
An ATAPI command is communicated by sending a Command Packet to the ATAPI CD-ROM Drive. For several commands, the Command Packet is accompanied by a list of parameters sent upon receiving an interrupt following the Command Packet being sent. See the specific commands for detailed information.
The Command Packet always has an operation code as its first byte.
For all commands, if there is an invalid parameter in the Command Packet, then the ATAPI Device shall abort the command without altering the medium.

Table 34 - Typical Command Packet for Most Commands
Bit
Byte
0
1
2
3
4
5
6
7-8

7

6

5

4

3

2

1

0

Operation Code
Reserved

Reserved

(MSB)
Logical Block Address (if required)
(LSB)
Reserved
Transfer Length (if required) or
Parameter List Length (if required) or
Allocation Length (if required)(LSB)
Reserved
Reserved
Reserved

(MSB)

9
10
11

Table 35 - Typical Command Packet for Some Extended Commands
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

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7

6

5

4

3

2

1

0

Operation Code
Reserved

Reserved

(MSB)
Logical Block Address (if required)
(LSB)
(MSB)
Transfer Length (if required) or
Parameter List Length (if required) or
Allocation Length (if required)
(LSB)
Reserved
Reserved

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ATAPI CD-ROM Specification
CD-ROM Packet Commands
10.2.1 Operation Code
The operation code of the Command Packet has a group code field and a command code field. The three-bit group code
field provides for eight groups of command codes. The five-bit command code field provides for thirty-two command
codes in each group. Thus, a total of 256 possible operation codes exist. Operation codes are defined in the subsequent
sections.

Table 36 - Operation Code
Bit

7

6
Group Code

5

4

3

2

1

0

Command Code

Note that the Group / Command code fields have been kept for backward compatibility and are not used by ATAPI.

10.2.2 Logical Block Address
The logical block address shall begin with block zero and be contiguous up to the last logical block.

10.2.3 Transfer Length
The Transfer Length Field specifies the amount of data to be transferred, usually the number of blocks. For several commands the transfer length indicates the requested number of bytes to be sent as defined in the command description. For
these commands the Transfer Length Field may be identified by a different name. See the following descriptions and the
individual command descriptions for further information.
In commands that use multiple bytes for the transfer length, a transfer length of zero indicates that no data transfer shall
take place. A value of one or greater indicates the number of blocks that shall be transferred.

10.2.4 Parameter List Length
The Parameter List Length is used to specify the number of bytes to be sent to the Drive. This field is typically used in
Command Packets for parameters that are sent to a Drive (e.g. mode parameters, diagnostic parameters, etc.). A parameter length of zero indicates that no data shall be transferred.

10.2.5 Allocation Length
The Allocation Length Field specifies the maximum number of bytes that a Host Computer has allocated for returned data. An allocation length of zero indicates that no data shall be transferred. The Drive shall terminate the data transfer
when allocation length bytes have been transferred or when all available data have been transferred to the Host Computer, whichever is less. The allocation length is used to limit the maximum amount of data (e.g. sense data, mode data,
etc.) returned to a Host Computer. When data is truncated, no error is generated, except for the Mechanism Status Command that shall generate a Parameter List Length Error.

10.3 Status
A Status byte shall be sent from the Drive to the Host Computer at the completion of each command unless the command is terminated by one of the following events:
1.

A hard reset condition.

2.

An unexpected event.

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CD-ROM Packet Commands
Immediate Command Processing Considerations

Status is normally presented at the end of a command, but in some cases may occur prior to transferring the Command
Packet.
For a description of the Status Byte see "Table 11 - ATAPI Status Register (ATA Status Register)" on page 55.

10.4 Immediate Command Processing Considerations
Immediate commands are a class of commands which return completion status to the host system before they are finished
executing the command. The purpose of immediate commands is to allow the host to execute more than one command at
a time on the same IDE cable. An example of a typical overlapped cd-rom command execution would be to Play audio
while accessing data from a disk drive on the same cable. In this example the host system would issue a Play Audio command. The ATAPI CD-Rom device would accept the command, and interrupt the host to return status. The host system is
now free to issue additional commands to any other device at the same IDE port address including the ATAPI device executing the immediate command.
ATAPI devices use the DSC bit to indicate the completion status of the seek operation of immediate commands. No INTRQ is issued by these device when the DSC bit is set, so it the responsibility of the ATAPI driver to poll this bit to determine the completion status of the immediate command. See also"5.6 Immediate Command Operation" on page 23.

10.5 Command Processing Considerations and Exception Conditions
The following sections describe some exception conditions and errors associated with command processing and the sequencing of commands.

10.5.1 Parameter Rounding
Certain parameters sent to an ATAPI CD-ROM Drive with various commands contain a range of values. ATAPI CDROM Drives may choose to implement only selected values from this range. When the ATAPI CD-ROM Drive receives
a value that it does not support, it either rejects the command (CHECK CONDITION status with ILLEGAL REQUEST
sense key) or it rounds the value received to a supported value. The ATAPI CD-ROM Drive shall reject unsupported values unless rounding is permitted in the description of the parameter.
Rounding of parameter values, when permitted1, shall be performed as follows - An ATAPI CD-ROM Drive that receives a parameter value that is not an exact supported value shall adjust the value to one that it supports and shall return
CHECK CONDITION status with a sense key of RECOVERED ERROR. The additional sense code shall be set to
ROUNDED PARAMETER. The Host Computer is responsible for issuing an appropriate command to learn what value
the ATAPI CD-ROM Drive has selected.

10.6 Unit Attention Condition
The ATAPI CD-ROM Drive shall generate a unit attention whenever the ATAPI CD-ROM Drive has been reset by a hard
reset condition, or by a power-on reset. The ATAPI CD-ROM Drive shall also generate a unit attention condition whenever one of the following events occurs:
1.

A removable Disc or Cartridge may have been changed.

2.

The version or level of microcode has been changed.

1. Generally, the ATAPI CD-ROM Drive should adjust maximum-value fields down to the next lower supported
value than the one specified by the Host Computer. Minimum-value fields should be rounded up to the next higher
supported value than the one specified by the Host Computer. In some cases, the type of rounding (up or down)
is explicitly specified in the description of the parameter.

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ATAPI CD-ROM Specification
CD-ROM Packet Commands
3.

INQUIRY or Packet Identify Drive Data has been changed.

4.

The mode parameters in effect for the Host Computer have been restored from non-volatile memory.

5.

Any other event occurs that requires the attention of the Host Computer.

6.

Any Disc or Cartridge has been manually moved within a Changer.

The ATAPI CD-ROM Drive may queue unit attention conditions. After the first unit attention condition is cleared, another unit attention condition may exist (e.g. a power on condition followed by a microcode change condition).
The unit attention condition shall persist, until the Host Computer clears the condition as described in the following paragraphs.
If an INQUIRY command is received from an Host Computer with a pending unit attention condition, the ATAPI CDROM Drive shall perform the INQUIRY command and shall not clear the unit attention condition.
If a REQUEST SENSE command is received from a Host Computer with a pending unit attention condition, then the
ATAPI CD-ROM Drive shall either:
1.

report any pending sense data and preserve the unit attention condition, or,

2.

report the unit attention condition, may discard any pending sense data, and clear the unit attention condition.

If an Host Computer issues a command other than INQUIRY or REQUEST SENSE while a unit attention condition exists for that Host, the ATAPI CD-ROM Drive shall not perform the command and shall report CHECK CONDITION
status unless a higher priority status as defined by the ATAPI CD-ROM Drive is also pending (e.g. BUSY).

10.7 Commands and Parameters
The ATAPI CD-ROM commands are derived from the SCSI CD-ROM command set.
With the exception of the CD-ROM MSF addressing technique, the interface uses logical rather than physical addressing
for all data blocks. Each Device may be interrogated to determine how many blocks it contains.
Commands are classified as mandatory, optional, or vendor-specific. ATAPI CD-ROM drives are required to implement
all mandatory commands and may implement other commands as well. ATAPI CD-ROM Drives contain commands that
facilitate the writing of self-configuring software drivers that can discover all necessary attributes without prior knowledge of specific peripheral characteristics (such as storage capacity).

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CD-ROM Packet Commands
ATAPI Packet Commands for CD-ROM Devices

10.8 ATAPI Packet Commands for CD-ROM Devices

Table 37 - Packet Commands Supported by CD-ROM Drives
Command Description
INQUIRY
LOAD/UNLOAD CD
MECHANISM STATUS
MODE SELECT (10)
MODE SENSE (10)
PAUSE/RESUME
PLAY AUDIO (10)
PLAY AUDIO MSF
PLAY CD
PREVENT/ALLOW MEDIUM REMOVAL
READ (10)
READ (12)
READ CD-ROM CAPACITY
READ CD
READ CD MSF
READ HEADER
READ SUB-CHANNEL
READ TOC
REQUEST SENSE
SCAN
SEEK
SET CD SPEED
STOP PLAY / SCAN
START STOP UNIT
TEST UNIT READY
Reserved for future use

Opcode
12h
A6h
BDh
55h
5Ah
4Bh
45h
47h
BCh
1Eh
28h
A8h
25h
BEh
B9h
44h
42h
43h
03h
BAh
2Bh
BBh
4Eh
1Bh
00h
BFh

Type
M
O**
M
M
M
O*
O*
O*
O
M
M
M
M
M
M
M
M
M
M
O
M
O
M
M
M

Reference
section 10.8.1 on page 93
section 10.8.2 on page 97
section 10.8.3 on page 99
section 10.8.4 on page 103
section 10.8.5 on page 105
section 10.8.7 on page 123
section 10.8.8 on page 125
section 10.8.9 on page 128
section 10.8.10 on page 131
section 10.8.11 on page 135
section 10.8.12 on page 137
section 10.8.13 on page 139
section 10.8.14 on page 141
section 10.8.15 on page 143
section 10.8.16 on page 155
section 10.8.17 on page 157
section 10.8.18 on page 161
section 10.8.19 on page 169
section 10.8.20 on page 179
section 10.8.21 on page 187
section 10.8.22 on page 191
section 10.8.23 on page 193
section 10.8.24 on page 195
section 10.8.25 on page 197
section 10.8.26 on page 199

Key: M = command implementation is mandatory.
O = command implementation is optional.
* = indicates a PLAY command. If any of the PLAY commands (indicated by an * in the type column) are implemented, all the PLAY commands shall be implemented by the ATAPI CD-ROM Drive.
** = indicates a Changer command. If any of the Changer commands (indicated by an ** in the type column)
are implemented, all the Changer commands shall be implemented by the ATAPI CD-ROM Drive. Note that
currently only the Load/Unload command has been defined.

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ATAPI CD-ROM Specification
INQUIRY Command
10.8.1 INQUIRY Command
The INQUIRY command requests that information regarding parameters of the ATAPI CD-ROM Drive be sent to the
Host Computer. An option allows the Host Computer to request additional information about the ATAPI CD-ROM Drive.

Table 38 - INQUIRY Command
Bit
Byte

7

6

0
1
2
3
4
5
6
7
8
9
10
11

5

4

3

Operation code (12h)
Reserved
Reserved
Reserved
Allocation Length
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved

2

1

0

Reserved

The INQUIRY command shall return CHECK CONDITION status only when the ATAPI CD-ROM Drive cannot return the requested INQUIRY data. The INQUIRY data should be returned even though the peripheral device may not be
ready for other commands.
If an INQUIRY command is received with a pending unit attention condition (i.e. before the ATAPI CD-ROM Drive reports CHECK CONDITION status), the ATAPI CD-ROM Drive shall perform the INQUIRY command and shall not
clear the unit attention condition.

10.8.1.1 Standard INQUIRY Data
The standard INQUIRY data contains 36 required bytes, followed by a variable number of vendor-specific parameters.
Bytes 56 through 95, if returned, are reserved for future standardization.

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ATAPI Packet Commands for CD-ROM devices
INQUIRY Command

Table 39 - INQUIRY Data Format
Bit
Byte
0
1
2
3
4
5
6
7
8
15
16
31
32
35
36
55
56
95

7

6

5

4

3

2

1

0

Reserved
Peripheral Device Type
RMB
Reserved
ISO Version
ECMA Version
ANSI Version (00)
ATAPI Version
Response Data Format
Additional Length (Number of bytes following this one)
Reserved
Reserved
Reserved
Vendor Identification
Product Identification
Product Revision Level
Vendor-specific
Reserved
Vendor Specific Parameters

96
n

The device-type fields identifies the device. It is defined in "Table 40 - Peripheral Device Types" on page 94.

10.8.1.2 Using the INQUIRY Command
The INQUIRY command may be used by a Host Computer to determine the configuration of the ATAPI CD-ROM
Drive. ATAPI CD-ROM Drives respond with information that includes their type and Specification level and may include the vendor’s identification, model number and other useful information.

Table 40 - Peripheral Device Types
Code
00h
01h - 04h
05h
06h
07h
08h - 1Eh
1Fh

Description
Direct-access device (e.g. magnetic disk)
Reserved
CD-ROM device
Reserved
Optical memory device (e.g. some optical disks)
Reserved
Unknown or no device type

The Peripheral Device Type shall be set to 05h to indicate a CD-ROM Device.
A Removable Medium Bit (RMB) of zero indicates that the medium is not removable. A RMB bit of one indicates that
the medium is removable. CD-ROM Devices should always report “Removable”.

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ATAPI CD-ROM Specification
INQUIRY Command

The usage of non-zero code values in the ISO version and ECMA version fields are defined by the International Organization for Standardization and the European Computer Manufacturers Association, respectively.
The ANSI-approved version field must contain a zero to comply with this version of the Specification.
The ATAPI Version field must contain 02h to comply with this version of the Specification.
A response data format value of 01h indicates that the data shall be in the format specified in this Specification. Response data format values greater than one are reserved.
The Additional Length field shall specify the length in bytes of the parameters. If the allocation length of the Command
Packet is too small to transfer all of the parameters, the additional length shall not be adjusted to reflect the truncation.
ASCII data fields shall contain only graphic codes (i.e. code values 20h through 7Eh). Left-aligned fields shall place any
unused bytes at the end of the field (highest offset) and the unused bytes shall be filled with space characters (20h).
Right-aligned fields shall place any unused bytes at the start of the field (lowest offset) and the unused bytes shall be
filled with space characters (20h).
The Vendor Identification field contains 8 bytes of ASCII data identifying the vendor of the product1. The data shall be
left aligned within this field.
The Product Identification field contains 16 bytes of ASCII data as defined by the vendor. The data shall be left-aligned
within this field.
The Product Revision Level field contains 4 bytes of ASCII data as defined by the vendor. The data shall be left-aligned
within this field.

Table 41 - Recommended Sense Key, ASC and ASCQ for Inquiry Command Errors
Sense Key

ASC

05

20

05

24

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET

1. It is intended that this field provide a unique vendor identification of the manufacturer of the ATAPI CD-ROM
Drive. In the absence of a formal registration procedure, X3T9.2 maintains a list of vendor identification codes in
use. Vendors are requested to voluntarily submit their identification codes to X3T9.2 to prevent duplication of
codes.

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INQUIRY Command

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ATAPI CD-ROM Specification
LOAD/UNLOAD CD Command
10.8.2 LOAD/UNLOAD CD Command
The LOAD / UNLOAD command requests that the ATAPI CD-ROM Drive changer load or unload a Disc. New Load /
Unload Commands issued before the changer posts STATE= (00) READY, will cause the changer to abort the Load /
Unload command in progress and begin processing the new Load / Unload CD command.

Table 42 - Load / Unload Command
Bit
Byte

7

6

0
1
2
3
4
5
6
7
8
9
10
11

Reserved

5

4

3

2

Operation code (A6h)
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
SLOT
Reserved
Reserved
Reserved

1

0

Immed

LoUnlo

Start

An immediate (Immed) bit of one indicates that the target shall return status as soon as the command descriptor block has
been validated. An Immed bit of zero indicates that the status shall not be returned until the operation has been completed.
A Start bit of one requests the Device be made ready for use. A Start bit of zero requests that the Device be stopped (media cannot be accessed by the Host Computer).

Table 43 - Load/Unload or Optional Selection Operations
LoUnlo

Start

0
0
1
1

0
1
0
1

Operation to be Performed
Abort any Prior Changer Command (Stop)
Reserved
Unload Media. The SLOT Parameter is ignored for this operation.

Either Move the Disc in the selected SLOT to the play position or select the
SLOT specified for use with future Media Access Commands

The SLOT field indicates the Slot to be loaded. Changers compatible with the Bootable CD-ROM specification should
always initialize (Load) Slot 0 on Power On or Bus Device Reset.
Any attempt to Load or Unload a Disc when the Drive does not support that capability shall result in an error condition
being reported to the Host (Sense key 05 ILLEGAL REQUEST, Sense Code 24 INVALID FIELD IN COMMAND
PACKET.)
Loading when the slot does not contain a Disc will be rejected with a Sense Key 02 (NOT READY) and Sense Code 3A
(MEDIUM NOT PRESENT). When this error is returned there are two possible actions by the CD Changer Device. If
the device reports Software Slot Selection (SSS) = 1, then the slot specified shall be selected for use. If the device reports

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ATAPI Packet Commands for CD-ROM devices
LOAD/UNLOAD CD Command

SSS = 0 then the previously used slot shall continue to selected for use.
If the drive is capable of caching data then a delayed load of a disc into the playing position can be supported.
If delayed loading of a disc into the playing position is supported, the device SHALL have previously cached the TOC
data from that disc. If the device has not read the TOC for a disc that is being loaded into the playing position, then delayed loading SHALL not be performed and the disc SHALL be loaded into the playing position immediately. If Caching
of TOC data has been performed and the loading of the Disc into the playing position is delayed, then the drive SHALL
report that the Disc is ready, even though the Disc is not spinning and installed in the playing position. In all cases the behavior seen by the host (other than a longer subsequent media access latency) shall not be different between delayed and
immediate loading of a disc.
Note that an UNIT ATTENTION Condition shall not be generated when discs are loaded or unloaded from the playing
position.
Unloading when the Play Position does not contain a Disc will be rejected with a Sense Key 05 (ILLEGAL REQUEST)
and Sense Code 24 (INVALID FIELD IN COMMAND) for the Slot Byte.

Table 44 - recommended Sense Key, ASC and ASCQ for Load / Unload CD
Sense
Key

ASC

02

05

05

20

05

24

05

01

06

28

06

29

Page 98

ASCQ

Description of Error
MEDIA LOAD OR EJECT FAILED
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
MECHANICAL POSITIONING OR CHANGER ERROR
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

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ATAPI CD-ROM Specification
MECHANISM STATUS Command
10.8.3 MECHANISM STATUS Command
The MECHANISM STATUS command requests that the ATAPI CD-ROM Drive respond with the current status of the
CD Device, including any Changer Mechanism that adheres to this specification. This command is intended to provide
information to the Host about the current operational state of the Device. The CD Devices take operational direction from
both the Host and the user (Person). Movement of media in/out of the device as well as Play type operations are at the
whim of the user. This command has been provided to allow the Host to know what as transpired at the user level.

Table 45 - MECHANISM STATUS Command
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

7

MSB

6

5

4

3

2

1

0

Operation code (BDh)
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Allocation Length
LSB
Reserved
Reserved

The Allocation Length field specifies the maximum length in bytes of the Slot Table Data that shall be transferred from
the ATAPI CD-ROM Drive to the Host Computer. A parameter list length of zero indicates that no data shall be transferred. This condition shall not be considered as an error.
The ATAPI CD-ROM Drive shall terminate the command with CHECK CONDITION status if the parameter list length
results in the truncation of any Mechanism Status header, or Slot Table page. The sense key shall be set to ILLEGAL
REQUEST, and the additional sense code shall be set to PARAMETER LIST LENGTH ERROR. Note: In the future,
this error may be removed.

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ATAPI Packet Commands for CD-ROM devices
MECHANISM STATUS Command

The Mechanism Status List contains a header, followed by zero or more fixed-length Slot Tables. If the device does not
support the changer commands, then the number of slot tables returned to the host shall be zero.

Table 46 - Mechanism Status Parameter List
Bit
Byte

7

6

5

0-7
8-n

4

3

2

1

0

2

1

0

Mechanism Status Header
Slot Table(s)

Each Slot Table contains the a slot number and status information.

Table 47 - Mechanism Status Header
Bit
Byte

7

0
1
2
3
4
5
6
7
8-n

Fault

6

5

4

3

Changer State
CD Mechanism State

Current Slot
Reserved

MSB
Current LBA
LSB
MSB

Number of Slots Available
Length of Slot Table(s)
LSB
Slot Tables (0-n)

Bit 0-4

Current Slot

This field indicates the current Changer Slot selected. Changers compatible
with a Bootable CD-ROM specification/standard, should always initialize
(Load) Slot 0 on Power On or Bus Device Reset. This value shall only be
changed when a Load Command is processed. Operations initiated by a user
shall not cause this value to change. If the device is not a changer, then this
field is reserved.

Bit 5-6

Changer State

This field indicates the current state of the changer. If the device is not a
changer, then this field is reserved.
0h = Ready
1h = Load in Progress
2h = Unload in Progress
3h = Initializing

Bit 7

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Fault

This bit indicates that the changer failed to complete the operation reported in
the Changer State field. If the device is not a changer, then this bit is reserved.

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ATAPI CD-ROM Specification
MECHANISM STATUS Command
Bit 7-5

CD Mechanism State

This field encodes the current operation of CD Mechanism. If the device is
not a changer, then this field is reserved.
0h
1h
2h
3h
4-6h
7h

Idle
Active with Audio Port in use (i.e. Playing Audio, Paused)
Audio Scan in progress
Active with Host, Composite or Other Ports in use (i.e. READ,
PLAY CD, SCAN during a PLAY CD)
Reserved
No State Information Available

The Current LBA value returns the location that was last used while reading or playing. Once a Read or Play operation
has been completed the value of this field may be undefined. While a Read or Play is in progress this field will contain
the LBA of the current block being processed.
The Number of Slots Available field shall return the number of physical Slots that the device supports.
The Length of Slot Tables field specifies the length in bytes of the all the slot information that follows (e.g. for a 2 slot
device this value would be 8).

Table 48 - Slot Table Response format
Bit
Byte
0

7

6

5

4

3

Disc
Present
(Optional)

2

1

0
Change
(Mandatory)

1
2
3

Reserved
Reserved
Reserved

Bit 0

Change

Change indicates that the Disc in that slot has been changed since the last
time the Disc was loaded.

Bit 7

Disc Present

This bit reports the presence of a Disc in a Slot, or if the Disc for a given Slot
is in the Playing Position. A value of 1 indicates the Disc is present, and 0 indicates that it is not.

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SDP=0

Changer devices may not support the capability of reporting the presence of a
Disc in each of the slots after reset or a cartridge change. In this case the Device must report this in the capabilities mode page (See "10.8.6.4 CD-ROM
Capabilities and Mechanical Status Page" on page 118 “Supports Disc
Present Reporting bit (SDP)”). In this case the device shall report that ALL
Discs are present, until the device can determine that there is no Disc present
(i.e. when a Load Command is processed for an empty slot).

SDP=1

If the Changer device does support the reporting of the Disc Present then this
bit shall be valid for all slots. It is not acceptable for the device to actually load
and unload each slot to compute this information.

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MECHANISM STATUS Command

Table 49 - Recommended Sense Key, ASC and ASCQ for Mechanism Status
Sense
Key

ASC

05

01

05

1A

05

20

05

26

06

28

06

29

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ASCQ

Description of Error
MECHANICAL POSITIONING OR CHANGER ERROR
PARAMETER LIST LENGTH ERROR
INVALID COMMAND OPERATION CODE
INVALID FIELD IN PARAMETER LIST
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

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ATAPI CD-ROM Specification
MODE SELECT Command
10.8.4 MODE SELECT Command
The MODE SELECT command provides a means for the Host Computer to specify medium, or peripheral device parameters to the ATAPI CD-ROM Drive. Host Computers shall issue MODE SENSE prior to each MODE SELECT to determine supported pages, page lengths, and other parameters.

Table 50 - Mode Select Command
Bit
Byte

7

0
1
2
3
4
5
6
7
8
9
10
11

6

Reserved

5

4

3

Operation code (55h)
1
Reserved
Reserved
Reserved
Reserved
Reserved
Parameter List Length (MSB)
Parameter List Length (LSB)
Reserved
Reserved
Reserved

2

Reserved

1

0

SP

A Save Pages (SP) bit of zero indicates the ATAPI CD-ROM Drive shall perform the specified MODE SELECT operation, and shall not save any pages. An SP bit of one indicates that the ATAPI CD-ROM Drive shall perform the specified MODE SELECT operation, and shall save to a non-volatile vendor-specific location all the savable pages. If an
ATAPI CD-ROM Drive supports saved pages, it shall save only one copy of the page. The SP bit is optional, even when
mode pages are supported by the ATAPI CD-ROM Drive. Pages that are saved are identified by the parameter savable
bit that is returned in the page header by the MODE SENSE command. If the PS bit is set in the MODE SENSE data
then the page shall be savable by issuing a MODE SELECT command with the SP bit set. If the ATAPI CD-ROM
Drive does not implement saved pages and the SP bit is set to one, the command shall be terminated with CHECK CONDITION status. The sense key shall be set to ILLEGAL REQUEST, and the additional sense code set to INVALID
FIELD IN COMMAND PACKET.
The Parameter List Length field specifies the length in bytes of the mode parameter list that shall be transferred from the
Host Computer to the ATAPI CD-ROM Drive after the Command Packet is transferred. A parameter list length of zero
indicates that no data shall be transferred. This condition shall not be considered as an error.
The ATAPI CD-ROM Drive shall terminate the command with CHECK CONDITION status if the parameter list length
results in the truncation of any mode parameter header, or mode page. The sense key shall be set to ILLEGAL REQUEST, and the additional sense code shall be set to PARAMETER LIST LENGTH ERROR.
The mode parameter list for the MODE SELECT and MODE SENSE commands is defined in "10.8.6 Mode Select/
Sense Parameters" on page 108.
The ATAPI CD-ROM Drive shall terminate the MODE SELECT command with CHECK CONDITION status, set the
sense key to ILLEGAL REQUEST, set the additional sense code to INVALID FIELD IN PARAMETER LIST, and
shall not change any mode parameters for the following conditions:
1.

If the Host Computer sets any field (except for reserved fields) that is reported as not changeable by the ATAPI
CD-ROM Drive to a value other than its current value.

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ATAPI Packet Commands for CD-ROM devices
MODE SELECT Command

2.

If the Host Computer sets any unreserved field in the mode parameter header to an unsupported value.

3.

If an Host Computer sends a mode page with a page length not equal to the page length returned by the MODE
SENSE command for that page.

4.

If the Host Computer sends an unsupported value for a mode parameter and rounding is not implemented for that
mode parameter.

If the Host Computer sends a value for a mode parameter that is outside the range supported by the ATAPI CD-ROM
Drive and rounding is implemented for that mode parameter, the ATAPI CD-ROM Drive may either:
1.

round the parameter to an acceptable value and terminate the command;

2.

terminate the command with CHECK CONDITION status, the sense key set to ILLEGAL REQUEST, and set the
additional sense code to INVALID FIELD IN PARAMETER LIST.

An ATAPI CD-ROM Drive may alter any mode parameter in any mode page (even those reported as non-changeable)
as a result of changes to other mode parameters1.
The ATAPI CD-ROM Drive validates the non-changeable mode parameters against the current values that existed for
those mode parameters prior to the MODE SELECT command.

Table 51 - Recommended Sense Key, ASC and ASCQ for Mode Select Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

06

2A

05

26

05

00

ASCQ

01
11

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED
MODE PARAMETER CHANGED
INVALID FIELD IN PARAMETER LIST
PLAY OPERATION IN PROCESS

1. If the current values calculated by the ATAPI CD-ROM Drive affect the Host Computer’s operation, the Host
Computer shall issue a MODE SENSE command after each MODE SELECT command.

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ATAPI CD-ROM Specification
MODE SENSE Command
10.8.5 MODE SENSE Command
The MODE SENSE command provides a means for an ATAPI CD-ROM Drive to report parameters to the Host Computer. It is a complementary command to the MODE SELECT command.

Table 52 - Mode Sense command
Bit
Byte

7

6

0
1
2
3
4
5
6
7
8
9
10
11

5

Reserved
PC

4

3

2

Operation code (5Ah)
Reserved
Reserved
Page Code
Reserved
Reserved
Reserved
Reserved
Allocation Length (MSB)
Allocation Length (LSB)
Reserved
Reserved
Reserved

1

0

Reserved

The Page Control (PC) field defines the type of mode parameter values to be returned in the mode pages. See sections
"10.8.5.1 Current Values" - "10.8.5.4 Saved Values" below.

Table 53 - Page Control Field
Code
00b
01b
10b
11b

Type of Parameter
Current values
Changeable values
Default values
Saved values

Section
10.8.5.1 on page 106
10.8.5.2 on page 106
10.8.5.3 on page 106
10.8.5.4 on page 106

NOTE The Page Control field only affects the mode parameters within the mode pages, however the PS bit, Page Code and Page Length fields shall
return current values since they have no meaning when used with other types. The mode parameter header shall return current values. (see also
"10.8.6 Mode Select/Sense Parameters" on page 108)

The Page Code specifies which mode page(s) to return1. See "Table 56 - Mode Page Codes for CD-ROM" on page 108
for a description of the Mode pages.
A Host Computer may request any one or all of the supported mode pages from an ATAPI CD-ROM Drive. If a Host
Computer issues a MODE SENSE command with a page code value not implemented by the ATAPI CD-ROM Drive,
the ATAPI CD-ROM Drive shall return CHECK CONDITION status and shall set the sense key to ILLEGAL REQUEST and the additional sense code to INVALID FIELD IN COMMAND PACKET.
A Page Code of 3Fh indicates that all mode pages implemented by the ATAPI CD-ROM Drive shall be returned to the
Host Computer. If the mode parameter list exceeds 65536 bytes for a MODE SENSE command, the ATAPI CD-ROM
Drive shall return CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST and the addition1. Mode pages shall be returned in ascending page code order except for mode page 00h.

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MODE SENSE Command

al sense code set to INVALID FIELD IN COMMAND PACKET.
Mode page 00h, if implemented, shall be returned after all other mode pages.

10.8.5.1 Current Values
A PC field value of 0h requests that the ATAPI CD-ROM Drive return the current values of the mode parameters. The
current values returned are:
1.

the current values of the mode parameters established by last successful MODE SELECT command.

2.

the saved values of the mode parameters if a MODE SELECT command has not successfully completed since the
last power-on, hard RESET condition.

3.

the default values of the mode parameters, if saved values, are not available or not supported.

10.8.5.2 Changeable Values
A PC field value of 1h requests that the ATAPI CD-ROM Drive return a mask denoting those mode parameters that are
changeable. In the mask, the fields of the mode parameters that are changeable shall be set to all one bits and the fields of
the mode parameters that are non-changeable (i.e. defined by the ATAPI CD-ROM Drive) shall be set to all zero bits.
An attempt to change a non-changeable mode parameter (via MODE SELECT) results in an error condition.
.
The Host Computer shall issue a MODE SENSE command with the PC field set to 1h and the Page Code field set to
3Fh to determine which mode pages are supported, which mode parameters within the mode pages are changeable, and
the supported length of each mode page prior to issuing any MODE SELECT commands.

10.8.5.3 Default Values
A PC field value of 2h requests that the ATAPI CD-ROM Drive return the default values of the mode parameters. Parameters not supported by the ATAPI CD-ROM Drive shall be set to zero. Default values are accessible even if the device is not ready.

10.8.5.4 Saved Values
A PC field value of 3h requests that the ATAPI CD-ROM Drive return the saved values of the mode parameters. Implementation of saved page parameters is optional. Mode parameters not supported by the ATAPI CD-ROM Drive shall be
set to zero. If saved values are not implemented, the command shall be terminated with CHECK CONDITION status,
the sense key set to ILLEGAL REQUEST and the additional sense code set to SAVING PARAMETERS NOT SUPPORTED.
The method of saving parameters is vendor-specific. The parameters are preserved in such a manner that they are retained when the ATAPI CD-ROM Drive is powered down. All savable pages can be considered saved when a MODE
SELECT command issued with the SP bit set to one has returned a “good” status.
Note: As CD-ROM devices do not have writable media and the media is removable, most will not support Saved Values. It is recommended that the
Host software not make use of saved pages.

10.8.5.5 Initial Responses
After a power-up condition or hard reset condition, the ATAPI CD-ROM Drive shall respond in the following manner:
1.

If default values are requested, report the default values.

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ATAPI CD-ROM Specification
MODE SENSE Command
2.

If saved values are requested, report valid restored mode parameters, or restore the mode parameters and report
them. If the saved values of the mode parameters are not able to be accessed from the non-volatile, vendorspecific location, terminate the command with CHECK CONDITION status and set the sense key set to NOT
READY. If saved parameters are not implemented, respond as defined in "10.8.5.4 Saved Values" on page 106.

If current values are requested and the current values of the mode parameters have not been sent by the Host Computer
(via a MODE SELECT command), the ATAPI CD-ROM Drive may return either the default or saved values as defined
above. If current values have been sent, the current values shall be reported.

Table 54 - Recommended Sense Key, ASC and ASCQ for Mode Sense Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

05

1A

05

39

working draft ATAPI

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED
PARAMETER LIST LENGTH ERROR
SAVING PARAMETERS NOT SUPPORTED

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Mode Select/Sense Parameters

10.8.6 Mode Select/Sense Parameters
This section describes the pages used with MODE SELECT and MODE SENSE commands.
The Mode Parameter List contains a header, followed by zero or more variable-length pages.

Table 55 - Mode Parameter List
Bit
Byte

7

6

5

0-n
0-n

4

3

2

1

0

Mode Parameter Header
Page(s)

Each mode page contains a page code, a page length, and a set of mode parameters.

Table 56 - Mode Page Codes for CD-ROM
Page code

Description

00h
01h
02h - 0Ch
0Dh
0Eh
2Ah
0Fh - 1Fh
20h-29h, 2Bh-3Eh
3Fh

Section

Vendor-specific (does not require page format)
Read error recovery page
Reserved
CD-ROM page
CD-ROM audio control page
CD-ROM Capabilities & Mechanical Status Page
Reserved
Vendor-specific (page format required)
Return all pages (valid only for the MODE SENSE command)

Type

10.8.6.3 on page 114

M

10.8.6.2 on page 113
10.8.6.1 on page 111
10.8.6.4 on page 118

M
M
M

Table 57 - Mode Page Format
Bit
Byte
0
1
2
n

7
PS/
Reserved

6

5

4

3

Reserved

2

1

0

Page Code
Page Length (n-1)
Mode Parameters

When using the MODE SENSE command, a Parameters Savable (PS) bit of one indicates that the mode page can be
saved by the ATAPI CD-ROM Drive in a non-volatile, vendor-specific location. A PS bit of zero indicates that the supported parameters cannot be saved. When using the MODE SELECT command, the PS bit is reserved.
The Page Code field identifies the format and parameters defined for that mode page.
When using the MODE SENSE command, if Page Code 00h (vendor-specific page) is implemented, the ATAPI CDROM Drive shall return that page last in response to a request to return all pages (page code 3Fh). When using the

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ATAPI CD-ROM Specification
Mode Select/Sense Parameters
MODE SELECT command, this page shall be sent last.
The Page Length field specifies the length in bytes of the mode parameters that follow. If the Host Computer does not
set this value to the value that is returned for the page by the MODE SENSE command, the ATAPI CD-ROM Drive
shall terminate the command with CHECK CONDITION status. The sense key shall be set to ILLEGAL REQUEST
with the additional sense code set to INVALID FIELD IN PARAMETER LIST. The ATAPI CD-ROM Drive is permitted to implement a mode page that is less than the full page length defined in this Specification, provided no field is truncated and the Page Length field correctly specifies the actual length implemented.
The mode parameters for each page are defined here. Mode parameters not implemented by the ATAPI CD-ROM Drive
shall be set to zero.

Table 58 - Mode Parameter Header
Bit
Byte

7

0
1
2
3
4
5
6
7

6

5

MSB

4

3

2

1

0

Mode Data Length
LSB
Medium Type
Reserved
Reserved
Reserved
Reserved

When using the MODE SENSE command, the mode data length field specifies the length in bytes of the following data
that is available to be transferred. The mode data length is the total byte count of all data following the mode data length
field. When using the MODE SELECT command, this field is reserved.

Table 59 - CD-ROM Media Type Codes
Code
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h - 0Fh
10h
11h
12h
13h
14h
15h
16h
17h

working draft ATAPI

Medium Type Description
Door closed / caddy inserted, medium type unknown
120 mm CD-ROM data only, door closed or caddy inserted
120 mm CD-DA audio only, door closed or caddy inserted
120 mm CD-ROM data and audio combined, door closed or caddy inserted
120 mm CD-ROM Hybrid disc (Photo CD), door closed or caddy inserted
80 mm CD-ROM data only, door closed or caddy inserted
80 mm CD-DA audio only, door closed or caddy inserted
80 mm CD-ROM data and audio combined, door closed or caddy inserted
80 mm CD-ROM Hybrid disc (Photo CD), door closed or caddy inserted
Reserved
Door closed / caddy inserted, medium type (CD-R) size unknown
120 mm CD-ROM (CD-R) data only, door closed or caddy inserted
120 mm CD-DA (CD-R) audio only, door closed or caddy inserted
120 mm CD-ROM (CD-R) data and audio combined, door closed or caddy inserted
120 mm CD-ROM (CD-R) Hybrid disc (Photo CD), door closed or caddy inserted
80 mm CD-ROM (CD-R) data only, door closed or caddy inserted
80 mm CD-DA (CD-R) audio only, door closed or caddy inserted
80 mm CD-ROM (CD-R) data and audio combined, door closed or caddy inserted

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Mode Select/Sense Parameters

Table 59 - CD-ROM Media Type Codes (Continued)
Code
18h
19h - 1Fh
20h
21h
22h
23h
24h
25h
26h
27h
28h
29h - 2Fh
30h
31h
32h - 34h
35h
36h - 6Fh
70h
71h
72h
73h - 7Fh
80h - FFh

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Medium Type Description
80 mm CD-ROM (CD-R) Hybrid disc (Photo CD), door closed or caddy inserted
Reserved
Door closed / caddy inserted, medium type (CD-E) size unknown
120 mm CD-ROM (CD-E) data only, door closed or caddy inserted
120 mm CD-DA (CD-E) audio only, door closed or caddy inserted
120 mm CD-ROM (CD-E) data and audio combined, door closed or caddy inserted
120 mm CD-ROM (CD-E Hybrid disc), door closed or caddy inserted
80 mm CD-ROM (CD-E) data only, door closed or caddy inserted
80 mm CD-DA (CD-E) audio only, door closed or caddy inserted
80 mm CD-ROM (CD-E) data and audio combined, door closed or caddy inserted
80 mm CD-ROM (CD-E) Hybrid disc, door closed or caddy inserted
Reserved
Door closed / caddy inserted, medium type unknown
120 mm (HD) door closed or caddy inserted
Reserved
80 mm (HD) door closed or caddy inserted
Reserved
Door closed, no disc present
Door open or no caddy inserted
Door closed or caddy inserted, medium format error
Reserved
Vendor-specific

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ATAPI CD-ROM Specification
Mode Select/Sense Parameters
10.8.6.1 CD-ROM Audio Control Parameters Page
The CD-ROM Audio Control Parameters Page sets the playback modes and output controls for subsequent PLAY AUDIO commands and any current audio playback operation.

Table 60 - CD-ROM Audio Control Mode Page Format
Bit
Byte
0

7
PS

6

5

Reserved

4

3

2

1

0

Immed

SOTC

Reserved

(Mandatory)
Always 1

(Mandatory)
Default 0

Page Code (0Eh)

(Optional)

1
2

3
4
5
6
7
8
9
10
11
12
13
14
15

Page Length (0Eh)
Reserved

Reserved
Reserved
Reserved
Logical Block Per Second of Audio Playback
Default 75
Reserved

CDDA Output Port 0 Channel Selection
Output Port 0 Volume (Mandatory) Default FFh
Reserved
CDDA Output Port 1 Channel Selection
Output Port 1 Volume (Mandatory) Default FFh
Reserved
CDDA Output Port 2 Channel Selection
Output Port 2 Volume (Optional) Default 00h
Reserved
CDDA Output Port 3 Channel Selection
Output Port 3 Volume (Optional) Default 00h

The Parameters Savable (PS) bit is only used with the MODE SENSE command. The PS bit is optional. This bit is reserved with the MODE SELECT command. A PS bit of one indicates that the ATAPI CD-ROM Drive is capable of saving the page in a non-volatile vendor-specific location.
The Immediate Bit (Immed) is used for information purposes only; the audio commands will always send completion
status as soon as the playback operation has been started. This bit shall always be set to 1.
A Stop On Track Crossing (SOTC) bit of zero indicates the ATAPI CD-ROM Drive shall terminate the audio playback
operation when the transfer length is satisfied. Multiple tracks shall be played as necessary. Periods of time encoded as
audio pause/silence at the beginning of tracks, (index 0) shall also be played. A SOTC bit of one indicates the ATAPI
CD-ROM Drive shall terminate the audio playback operation when the beginning of a following track is encountered.
The SOTC bit is mandatory.
The CDDA Output Port Channel Selection field specifies the Red Book audio channels from the disc to which a specific
output port shall be connected. More than one output port may be connected to an audio channel. More than one audio
channel may be connected to an output port.

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Mode Select/Sense Parameters

Table 61 - CDDA Output Port Channel Selection Codes
Code
0000b
0001b
0010b
0011b
0100b
1000b

Description
Output port muted
Connect audio channel 0 to this output port
Connect audio channel 1 to this output port
Connect audio channel 0 and audio channel 1 to this output port
Connect audio channel 2 to this output port
Connect audio channel 3 to this output port

The Output Port Volume Control indicates the relative volume level for this audio output port. The value used is specified as an attenuation of the normal volume level. A value of zero indicates the minimum volume level (Mute), and a value of FFh indicates maximum volume (No attenuation) level. It is recommended that the MUTE and volume functions
should be supported on a per channel basis. The attenuation used shall be as specified in "Table 62 - Attenuation Levels
for Audio". All values not shown in the table shall be valid, with the attenuation selected by interpolating using the
known table values.
It is recommended that the Drive support at least 16 volume levels. The actual attenuation levels for any given Binary attenuation value shall be given by the following equation: 20 Log (Binary Level / 256)
Note: Audio channel volume control regarding channel selection of MUTE vs. Volume Level setting of 0. It is recommend that drives allow the setting
of the Channel Selection fields to MUTE and also allow the setting of the Volume Level field to 0. It is up to the drive to determine how to shut off the
volume, either via muting circuitry or via the volume control.

.

Table 62 - Attenuation Levels for Audio
Binary Level
FFh
F0h
E0h
C0h
80h
40h
20h
10h
0Fh
0Eh
0Ch
08h
04h
02h
01h
00h

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Attenuation
0db (On)
-0.56
-1.16
-2.50
-6.00
-12.0
-18.0
-24.0
-24.6
-25.2
-26.6
-30.0
-36.0
-42.1
-48.0
Mute (Off)

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ATAPI CD-ROM Specification
Mode Select/Sense Parameters
10.8.6.2 CD-ROM Device Parameters Page
The CD-ROM Device parameters page specifies parameters that affect all CD-ROM data types.

Table 63 - CD-ROM Parameters Page Format
Bit
Byte
0

1
2
3
4
5
6
7

7

6

PS
(Optional)
Default 0

5

4

3

Reserved

2

1

0

Page Code (0Dh)

Page Length (06h)
Reserved
Reserved
MSB
MSB

Inactivity Time Multiplier
Number of MSF - S Units per MSF - M Unit
Default 60 (3Ch)
Number of MSF - F Units per MSF - S Unit
Default 75 (4Bh)

LSB
LSB

The Parameters Savable (PS) bit is only used with the MODE SENSE command. This bit is reserved with the MODE
SELECT command. A PS bit of one indicates that the ATAPI CD-ROM Drive is capable of saving the page in a nonvolatile vendor-specific location. The PS bit is optional.
The Inactivity Timer Multiplier specifies the length of time that the drive shall remain in the hold track state after completion of a seek or read operation.
NOTE Higher values in this parameter may have an adverse effect on the drive MTBF, in some implementations.

Table 64 - Inactivity Time Multiplier Values
Inactivity Timer
Multiplier
0h
1h
2h
3h
4h
5h
6h
7h

Minimum Time
in Hold Track
State
Vendor-specific
125 ms
250 ms
500 ms
1s
2s
4s
8s

Inactivity Timer

Minimum Time in

Multiplier

Hold Track State

8h
9h
Ah
Bh
Ch
Dh
Eh
Fh

16s
32s
1 min
2 min
4 min
8 min
16 min
32 min

The number of S units per M unit field gives the ratio of these MSF address values. For media conforming to the CDROM and CD-DA Specification, this value is 60.
The number of F units per S unit field gives the ratio of these MSF address values. For media conforming to the CDROM and CD-DA Specification, this value is 75.

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Mode Select/Sense Parameters

10.8.6.3 Read Error Recovery Parameters Page
The Read Error Recovery Parameters Page specifies the error recovery parameters the ATAPI CD-ROM Drive shall use
during any command that performs a data read operation from the media (e.g. READ, READ TOC, etc.).

Table 65 - Read Error Recovery Parameters Page Format
Bit
Byte
0

7

6

PS
(Optional)
Default 0

5

Reserved

Reserved

3

2

1

0

DTE

DCR

Page Code (01h)

1
2
3
4
5
6
7

4

TB

Page Length (06h)
Error Recovery Parameter, Default 0
RC
Reserved
PER
Read Retry Count
Reserved
Reserved
Reserved
Reserved

The Parameters Savable (PS) bit is only used with the MODE SENSE command. This bit is reserved with the MODE
SELECT command. A PS bit of one indicates that the ATAPI CD-ROM Drive is capable of saving the page in a nonvolatile vendor-specific location. The PS bit is optional.
NOTE The implementation of error recovery procedures for CD-ROM devices is markedly different from those used for magnetic medium disk drives.
At least one level of error correction (i.e. CIRC) is required to transfer the data stream. Therefore, the performance of the drive may differ substantially from what would be expected by sending the same error recovery parameters to a magnetic medium device.

A Transfer Block (TB) bit of one indicates that a data block that is not recovered within the recovery limits specified,
shall be transferred to the Host Computer before CHECK CONDITION status is returned. A TB bit of zero indicates that
such a data block shall not be transferred to the Host Computer. The TB bit does not affect the action taken for recovered
data.
A Read Continuous (RC) bit of one indicates that the CD-ROM drive shall transfer the entire requested length of data
without adding delays to perform error recovery procedures. This implies that the CD-ROM drive may send data that is
erroneous or fabricated in order to maintain a continuous flow of data. A RC bit of zero indicates that error recovery operations that cause delays are acceptable during the data transfer.
A Post Error (PER) bit of one indicates that the CD-ROM drive shall report recovered errors. A PER bit of zero indicates
that the CD-ROM drive shall not report recovered errors. Error recovery procedures shall be performed within the limits established by the error recovery parameters.
A Disable Transfer on Error (DTE) bit of one indicates that the CD-ROM drive shall terminate the data transfer to the
Host upon detection of a recovered error. A DTE bit of zero indicates that the CD-ROM drive shall not terminate the
data transfer upon detection of a recovered error.
A Disable Correction (DCR) bit of one indicates that error correction codes shall not be used for data error recovery. A
DCR bit of zero allows the use of error correction codes for data error recovery.
The correlation of the error recovery parameter and the bit settings defined for CD-ROM devices is given in "Table 66 Error Recovery Bit Settings" on page 115. The interpretation of these bit settings for CD-ROM devices is given in "Table
67 - CD-ROM Error Recovery Descriptions" on page 115. If the error recovery parameter is set to any other value, the

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ATAPI CD-ROM Specification
Mode Select/Sense Parameters
command shall be terminated with CHECK CONDITION status. The sense key shall be set to ILLEGAL REQUEST
and the additional sense code set to INVALID FIELD IN PARAMETER LIST.

Table 66 - Error Recovery Bit Settings
Error Recovery
Parameter
00h
01h
04h
05h
06h
07h
10h
11h
14h
15h

Bit Settings
76543210

Error Recovery
Parameter

Bit Settings
76543210

20h
RR10R000
21h
RR10R001
24h
RR10R100
25h
RR10R101
26h
RR10R110
27h
RR10R111
30h
RR11R000
31h
RR11R001
34h
RR11R100
35h
RR11R101
NOTE Reserved bits shall be set to zero.

RR00R000
RR00R001
RR00R100
RR00R101
RR00R110
RR00R111
RR01R000
RR01R001
RR01R100
RR01R101

Table 67 - CD-ROM Error Recovery Descriptions
Code
00h

01h

04h

05h

Error Recovery Description
The maximum error recovery procedures available are used. If an error occurs which is uncorrectable with the error correction codes (ECC) on the media, data transfer is terminated with CHECK CONDITION status. The block with the error
is not transferred. The sense key is set to MEDIUM ERROR. The information bytes give the address of the block where
the unrecovered error was detected. Recovered errors are not reported.
Only retries of the read operation and CIRC are used (layered error correction is not used). Only CIRC unrecovered data
errors are reported. If a CIRC unrecovered data error occurs, data transfer is terminated with CHECK CONDITION status.
The block with the error is not transferred. The sense key is set to MEDIUM ERROR. The information bytes give the
address of the block where the unrecovered error was detected. Recovered errors are not reported.
The maximum error recovery procedures available are used. Recovered data errors are reported. If a recovered data error
occurs, data transfer is not terminated. However, when the data transfer has completed CHECK CONDITION status is
reported. The sense key is set to RECOVERED ERROR. The information bytes give the address of the last block where a
recovered data error was detected. If a data error occurs that is uncorrectable with the ECC information available on the
media, data transfer is terminated and CHECK CONDITION status is reported. The block with the error is not transferred.
The sense key is set to MEDIUM ERROR. The information bytes give the address of the block where the uncorrectable
error was detected.
Only retries of the read operation and CIRC are used (layered error correction is not used). Recovered data errors are
reported. If a recovered data error occurs, data transfer is not terminated. However, when the data transfer has completed
CHECK CONDITION status is reported. The sense key is set to RECOVERED ERROR. The information bytes give the
address of the last block where a CIRC recovered data error was detected. If an unrecovered data error occurs, data transfer is terminated and CHECK CONDITION status is reported. The block with the error is not transferred. The sense key is
set to MEDIUM ERROR. The information bytes give the address of the block where the unrecovered error was detected.

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Mode Select/Sense Parameters

Table 67 - CD-ROM Error Recovery Descriptions
Code
06h

07h

10h

11h

14h

15h

20h

21h

24h

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Error Recovery Description
The maximum error recovery procedures are used. Recovered data errors are reported. If a recovered data error occurs data
transfer is terminated and CHECK CONDITION status is reported. The block with the recovered error is not transferred.
The sense key is set to RECOVERED ERROR. The information bytes give the address of the block where the recovered
data error was detected. If a data error occurs that is uncorrectable with the ECC information on the medium, data transfer
is terminated with CHECK CONDITION status. The block with the error is not transferred. The sense key is set to
MEDIUM ERROR. The information bytes give the address of the block where the uncorrectable error was detected.
Only retries of the read operation are used (layered error correction is not used) and CIRC recovered data errors are
reported. If a CIRC recovered data error occurs, data transfer is terminated with CHECK CONDITION status. The block
with the recovered error is not transferred. The sense key is set to RECOVERED ERROR. The information bytes give the
address of the block where the recovered data error was detected. If a CIRC unrecovered data error occurs, data transfer is
terminated with CHECK CONDITION status. The block with the error is not transferred. The sense key is set to
MEDIUM ERROR. The information bytes give the address of the block where the unrecovered error was detected.
If data transfer can be maintained, the maximum error recovery procedures available are used. (RC = 1.) If an error occurs
which is uncorrectable with the error correction codes (ECC) on the media, or is uncorrectable in time to maintain data
transfer, the data transfer is not terminated. However, when the data transfer has completed, CHECK CONDITION status
is reported. The sense key is set to MEDIUM ERROR. The information bytes give the address of the block where the first
unrecovered error was detected. Recovered errors are not reported.
If data transfer can be maintained, retries of the read operation and CIRC are used (layered error correction is not used).
(RC = 1.) Only CIRC unrecovered data errors are reported. If a CIRC unrecovered data error occurs, data transfer is not
terminated. However, when the data transfer has completed, CHECK CONDITION status is reported. The sense key is set
to MEDIUM ERROR. The information bytes give the address of the block where the first unrecovered error was detected.
Recovered errors are not reported.
If data transfer can be maintained, the maximum error recovery procedures available are used. (RC = 1.) Recovered data
errors are reported. If a recovered data error occurs, data transfer is not terminated. However, when the data transfer has
completed, CHECK CONDITION status is reported. The sense key is set to RECOVERED ERROR. The information
bytes give the address of the block where a recovered data error was detected. If an data error occurs that is uncorrectable
with the ECC information available on the media, or is uncorrectable in time to maintain data transfer, the data transfer is
not terminated. However, when the data transfer has completed CHECK CONDITION, status is reported. The sense key is
set to MEDIUM ERROR. The information bytes give the address of the block where the first uncorrectable error was
detected. Reporting unrecovered errors takes precedence over reporting recovered errors.
If data transfer can be maintained, retries of the read operation and CIRC are used (layered error correction is not used).
(RC = 1.) Recovered data errors are reported. If a recovered data error occurs, data transfer is not terminated. However,
when the data transfer has completed CHECK CONDITION status is reported. The sense key is set to RECOVERED
ERROR. The information bytes give the address of the block where a CIRC recovered data error was detected. If an unrecovered data error occurs, data transfer is not terminated. However, when the data transfer has completed CHECK CONDITION status is reported. The sense key is set to MEDIUM ERROR. The information bytes give the address of the block
where the first unrecovered error was detected. Reporting unrecovered errors takes precedence over reporting recovered
errors.
The maximum error recovery procedures available are used. If an error occurs which is uncorrectable with the error correction codes (ECC) on the media, data transfer is terminated with CHECK CONDITION status. The block with the error
is transferred. The sense key is set to MEDIUM ERROR. The information bytes give the address of the block where the
unrecovered error was detected. Recovered errors are not reported.
Only retries of the read operation and CIRC are used (layered error correction is not used). Only CIRC unrecovered data
errors are reported. If a CIRC unrecovered data error occurs data transfer is terminated with CHECK CONDITION status.
The block with the error is transferred. The sense key is set to MEDIUM ERROR. The information bytes give the address
of the block where the unrecovered error was detected. Recovered errors are not reported.
The maximum error recovery procedures available are used. Recovered data errors are reported. If a recovered data error
occurs data transfer is not terminated. However, when the data transfer has completed, CHECK CONDITION status is
reported. The sense key is set to RECOVERED ERROR. The information bytes give the address of the last block where a
recovered data error was detected. If a data error occurs that is uncorrectable with the ECC information available on the
media data transfer is terminated and CHECK CONDITION status is reported. The block with the error is transferred. The
sense key is set to MEDIUM ERROR. The information bytes give the address of the block where the uncorrectable error
was detected.

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ATAPI CD-ROM Specification
Mode Select/Sense Parameters
Table 67 - CD-ROM Error Recovery Descriptions
Code
25h

26h

27h

30h
31h
34h
35h

Error Recovery Description
Only retries of the read operation and CIRC are used (layered error correction is not used). Recovered data errors are
reported. If a recovered data error occurs, data transfer is not terminated. However, when the data transfer has completed,
CHECK CONDITION status is reported. The sense key is set to RECOVERED ERROR. The information bytes give the
address of the last block where a CIRC recovered data error was detected. If an unrecovered data error occurs, data transfer is terminated and CHECK CONDITION status is reported. The block with the error is transferred. The sense key is set
to MEDIUM ERROR. The information bytes give the address of the block where the unrecovered error was detected.
The maximum error recovery procedures are used. Recovered data errors are reported. If a recovered data error occurs,
data transfer is terminated and CHECK CONDITION status is reported. The block with the recovered error is transferred.
The sense key is set to RECOVERED ERROR. The information bytes give the address of the block where the recovered
data error was detected. If a data error occurs that is uncorrectable with the ECC information on the media, data transfer is
terminated with CHECK CONDITION status. The block with the error is transferred. The sense key is set to MEDIUM
ERROR. The information bytes give the address of the block where the uncorrectable error was detected.
Only retries of the read operation are used (layered error correction is not used). CIRC recovered data errors are reported.
If a CIRC recovered data error occurs, data transfer is terminated with CHECK CONDITION status. The block with the
recovered error is transferred. The sense key is set to RECOVERED ERROR. The information bytes give the address of
the block where the recovered data error was detected. If a CIRC unrecovered data error occurs, data transfer is terminated
with CHECK CONDITION status. The block with the error is transferred. The sense key is set to MEDIUM ERROR. The
information bytes give the address of the block where the unrecovered error was detected.
Same as code 10H.
Same as code 11H.
Same as code 14H.
Same as code 15H.

The Read Retry Count field specifies the number of times that the controller shall attempt its read recovery algorithm.
A CIRC Recovered Data Error is defined as a block for which the CIRC based error correction algorithm was unsuccessful for a read attempt, but on a subsequent read operation no error was reported. The number of subsequent read operations is limited to the read retry count. Layered error correction was not used.
A CIRC Unrecovered Data Error is defined as a block for which the CIRC based error correction algorithm was unsuccessful on all read attempts up to the read retry count. Layered error correction was not used.
An L-EC Recovered Data Error is defined as a block for which the CIRC based error correction algorithm was unsuccessful, but the layered error correction was able to correct the block within the read retry count.
An L-EC Uncorrectable Data Error is defined as a block which could not be corrected by layered error correction within
the read retry count.

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ATAPI Packet Commands for CD-ROM devices
Mode Select/Sense Parameters

10.8.6.4 CD-ROM Capabilities and Mechanical Status Page
The Capabilities Page is read only and may not be set with Mode Select.

Table 68 - CD-ROM Capabilities and Mechanical Status Page Format
Bit
Byte

7

6

0
1
2
3
4

PS

Reserved

5

Reserved

5

Reserved

Multi
Session
UPC

4

3

2

Page Code (2Ah)
Page Length (12h)
Method 2

Reserved
Reserved
Mode 2
Mode 2
Form 2
Form 1
ISRC
C2 Pointers

Digital
Port(2)
R-W Deinterleaved

Digital
Port(1)
R-W Supported

1

0

CD-E Rd
CD-E Wr
Composite

CD-R Rd
CD-R Wr
AudioPlay

DAAccu

CD DA

Lock
State
Separate
Channel
Mute

Lock

& corrected

6

Loading Mechanism Type

7

8
9
10
11
12
13
14
15
16
17
18
19

Reserved

Reserved

Eject
S/W Slot
Selection
(SSS)

Prevent
Jumper
Supports
Disc
Present
(SDP)

Separate
volume

(MSB)
Maximum Speed Supported (in KBps)

(LSB)

Number of Volume Levels Supported

(LSB)

Buffer Size supported by Drive (in KBytes)

(LSB)

Current Speed Selected (in KBps)
Reserved
Length
LSBF
Reserved
Reserved

(LSB)

(MSB)
(MSB)
(MSB)

Reserved

RCK

BCK

Reserved

Media Function Capabilities:
If CD-R Read Field is set to one, the drive shall support the read function of CD-R disc (Orange Book Part II).
If CD-E Read Field is set to one, the drive shall support the read function of CD-E disc (Orange Book Part III).
If Method 2 is set to one, the drive shall support the read function of CD-R media written using fixed packet tracks using
Addressing Method 2.
If CD-R Write Field is set to one, the drive shall support the write function of CD-R disc (Orange Book Part II).
If CD-E Write Field is set to one, the drive shall support the write function of CD-E disc (Orange Book Part III).
The individual capabilities of the drive are specified by bytes 4 through 7. Each of the bits indicate if that specific capability is supported. A value of zero indicates that the capability is NOT supported; a value of one indicates the capability
IS supported.

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Mode Select/Sense Parameters

Bit 0

Audio Play

The drive is capable of Audio Play operation. This also indicates that the
drive is capable of overlapping Play and other commands such as reading of
the Sub-channel information.

Bit 1

Composite

The drive is capable of delivering a composite Audio and Video data stream.

Bit 2

Digital Port(1)

The drive supports digital output (IEC958) on port 1

Bit 3

Digital Port(2)

The drive supports digital output(IEC958) on port 2

Bit 4

Mode 2 Form 1

The drive is capable of reading sectors in Mode 2 Form 1 (XA) format.

Bit 5
Bit 6

Mode 2 Form 2
Multi Session

The drive is capable of reading sectors in Mode 2 Form 2 format.
The drive is capable of reading multiple session or Photo-CD discs.

Bit 8

CD-DA Commands
Supported

Red Book audio can be read using the READ-CD command.

Bit 9

CD-DA Stream is Accurate

This bit indicates that the drive supports an advanced feature that allows it to
return to an audio location without losing place to continue the READ CD-DA
command.
0
The drive is incapable of accurately restarting the CD-DA read operation, and a BUFFER OVERFLOW error shall be reported whenever a
loss of streaming occurs. This error will be fatal and the command will
have to be repeated from the beginning.
1
The drive can continue from a loss of streaming condition and no error
will be generated.

Bit 10

R-W Supported

The commands that return Sub-channel data can return the combined R-W information.

Bit 11

R-W De-interleaved &
Corrected

This indicates that the R-W sub-channel data will be returned de-interleaved
and error corrected.

Bit 12

C2 Pointers are Supported

Bit 13

ISRC

This indicates that the drive supports the C2 Error Pointers. This also indicates that the drive is capable of returning the C2 Error Pointers and C2 Block
Error flags in the READ CD command.
The drive can return the International Standard Recording Code Information.

Bit 14

UPC

The drive can return the Media Catalog Number (UPC)

Bit 16

Lock

The PREVENT/ALLOW command is capable of actually locking the media
into the drive.

Bit 17

Lock State

This indicates the current state of the drive.
0
The drive is currently in the allow (Unlocked) state. Media may be inserted or ejected.
1
The drive is currently in the prevent (Locked) state. Media loaded in
the drive may not be removed via a soft or hard eject. If the drive is
empty, media may not be inserted if the Prevent Jumper is not present.
If the jumper is present, then media may be inserted.

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Mode Select/Sense Parameters

Bit 18

Prevent Jumper

This indicates the state of the (Optional) Prevent/Allow Jumper.
0
Jumper is present. Drive will power up to the allow state. Locking the
drive with the Prevent/Allow Command shall NOT prevent the insertion of media.
1
Jumper is not present. Drive will power up to the Prevent State
(Locked). The drive will not accept new media or allow the ejection of
media already loaded until an allow command is issued.

Bit 19

Eject Command

The drive can eject the disc via the normal START/STOP command with the
LoEj bit set. If the mechanism is a Changer that uses a Cartridge, then this bit
indicates that the Cartridge can be ejected.

Bit 20

Reserved

Reserved

Bit 23-21 Loading Mechanism Type

This field specifies the type of disc loading the drive supports.
23 22 21
0 0 0 Caddy type loading mechanism
0 0 1 Tray type loading mechanism
0 1 0 Pop-up type loading mechanism
0 1 1 Reserved
1 0 0 Changer with individually changeable discs
1 0 1 Changer using a Cartridge Mechanism
1 1 0 Reserved
1 1 1 Reserved

Bit 24

Separate Volume Levels

The audio level for each channel can be controlled independently.

Bit 25

Separate Channel Mute

The mute capability for each channel can be controlled independently.

Bit 26

Supports Disc Present (SDP)

This bit indicates that the Device contains an embedded changer, and that after
a reset condition or if a cartridge is changed, it can report the exact contents
of the slots. The response to the MECHANISM STATUS command will contain valid Disc is Present status information for all slots.

Bit 27

Software Slot Selection (SSS) This bit controls the behavior of the LOAD/UNLOAD command when trying
to load a Slot with no Disc present (see "Table 43 - Load/Unload or Optional
Selection Operations" on page 97).

The Maximum Speed Supported field indicates the actual maximum data rate that the drive supports. This value is re-

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Mode Select/Sense Parameters
turned as the number of kilobytes per/second (Speed/1000) that the data is read from the drive.

Table 69 - Example Data Rates
Speed

Data Rate

X1
X2
X2.2
X3
X4
X8
X16

176 KBytes/second
353 KBytes/second
387 KBytes/second
528 KBytes/second
706 KBytes/second
1.4 MBytes/second
2.8 MBytes/second

Note that these are the raw data rates and do not reflect any overhead resulting from headers, error correction data, etc. It
is also important to understand that the reported data rate is a theoretical maximum and the actual data rates to the host
will be lower. The data rates are dynamic and will change as the drive changes its speed.
The Number of Volume Levels Supported field returns the number of discrete levels. If the drive only supports turning
audio on and off, the Number of Volume Levels field shall be set to 2.
The Buffer Size Supported field returns the number of bytes of buffer dedicated to the data stream returned to the Host
Computer. This value is returned in Kbytes (Size/1024). If the drive does not have a buffer cache, the value returned
shall be zero.
The Current Speed Selected field indicates the actual data rate that the drive is currently using. This value is returned as
the number of kilobytes per/second (Speed/1000) that the data is read from the drive.

Byte 17 is used to describe the format of the drives digital output.
Bit 1

BCKF

Set if data valid on the falling edge of the BCK signal. Clear if data valid on
the rising edge of the BCK signal

Bit 2

RCK

Set if HIGH on LRCK indicates left channel. Clear if HIGH on LRCK indicates right channel.

Bit 3

LSBF

Set if LSB first. Clear if MSB first.

Bit 4-5

Length

00
01
10
11

working draft ATAPI

32 BCKs
16 BCKs
24 BCKs
24 BCKs (I2S)

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ATAPI CD-ROM Specification
PAUSE/RESUME Command
10.8.7 PAUSE/RESUME Command
The PAUSE/RESUME command requests that the device stop or start an audio play operation. This command is used
with PLAY AUDIO commands that are currently executing.

Table 70 - PAUSE/RESUME Command
Bit
Byte

7

6

0
1
2
3
4
5
6
7
8
9
10
11

5

4

3

2

1

Operation Code (4Bh)
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved

0

Resume

A Resume bit of zero causes the drive to enter the hold track state with the audio output muted after the current block is
played. A Resume bit of one causes the drive to release the pause/scan and begin play at the block following the last
block played/scanned.
If an audio play operation cannot be resumed and the resume bit is one, the command is terminated with CHECK CONDITION status. If the resume bit is zero and an audio play operation cannot be paused, (no audio play operation has
been requested, or the requested audio play operation has been completed), the command is terminated with CHECK
CONDITION status. See "Figure 15 - Stop Play/Play Audio/Audio Scan/Pause/Resume Sequencing" on page 196 for additional information.
It shall not be considered an error to request a PAUSE when a pause is already in effect or to request a RESUME when a
play operation is in progress.

Table 71 - Recommended Sense Key, ASC and ASCQ for Pause/Resume Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
3A

0B

B9

working draft ATAPI

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

MEDIUM NOT PRESENT
PLAY OPERATION ABORTED

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ATAPI CD-ROM Specification
PLAY AUDIO Command
10.8.8 PLAY AUDIO Command
The PLAY AUDIO command requests that the ATAPI CD-ROM Drive begin an audio playback operation. The command function and the output of audio signals shall be as specified by the settings of the mode parameters, including the
SOTC bit.

Table 72 - PLAY AUDIO Command
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

7

6

5

4

3

2

1

0

Operation Code (45h)
Reserved
MSB
Starting Logical Block Address
LSB
MSB

Reserved
Transfer Length
LSB
Reserved
Reserved
Reserved

This command responds with immediate status, allowing overlapped commands. This command shall set the DSC bit
upon command completion. See also "10.4 Immediate Command Processing Considerations" on page 90.
If any commands related to audio operations are implemented then the PLAY AUDIO (10) command shall be implemented to allow a method for the Host Computer to determine if audio operations are supported. An ATAPI CD-ROM
Drive responding to a PLAY AUDIO (10) command that has a transfer length of zero with CHECK CONDITION status
and setting the sense key to ILLEGAL REQUEST does not support audio play operations.
The Starting Logical Block Address field specifies the logical block at which the audio playback operation shall begin.
PLAY AUDIO commands with a starting logical block address of FFFF FFFFh shall implement audio play from the current location of the optics. PLAY AUDIO commands with a starting LBA address of 0000 0000h shall begin the audio
play operation at 00m 02s 00f.
The Transfer Length Field specifies the number of contiguous logical blocks that shall be played. A Transfer Length
Field of zero indicates that no audio operation shall occur. This condition shall not be considered an error.
If the starting address is not found, if the address is not within an audio track, or if a not ready condition exists, the command shall be terminated with CHECK CONDITION status.
If the CD-ROM information type (data vs. audio) changes within the transfer length, the command shall be terminated
with a CHECK CONDITION and the sense key shall be set to ILLEGAL REQUEST and the additional sense code set to
END OF USER AREA ENCOUNTERED ON THIS TRACK.
If the logical block address requested is not within an audio track, the command shall be terminated with CHECK CONDITION status. The sense key shall be set to ILLEGAL REQUEST and the additional sense code set to ILLEGAL
MODE FOR THIS TRACK.

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ATAPI Packet Commands for CD-ROM devices
PLAY AUDIO Command

Table 73 - Recommended Sense Key, ASC and ASCQ for Play Audio Command Errors
Sense Key

ASC

ASCQ

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
3A

00
01
02
03

02

06

00

03

02

05

21

05

63

05

64

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED
LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

MEDIUM NOT PRESENT
NO REFERENCE POSITION FOUND (media may be upside down)
NO SEEK COMPLETE
LOGICAL BLOCK ADDRESS OUT OF RANGE
END OF USER AREA ENCOUNTERED ON THIS TRACK
ILLEGAL MODE FOR THIS TRACK OR INCOMPATIBLE MEDIUM

10.8.8.1 Play Audio with Immediate Packet Commands
The PLAY AUDIO and AUDIO SCAN commands will continue to play while other commands are processed by the
drive. Some commands can be accepted without disrupting the audio operations, while others will cause the Play operation to stop. The following section describes the operation of other commands while playing audio.
A PLAY AUDIO and AUDIO SCAN command will be terminated when any of the commands in "Table 74 - Commands That Will Stop a Play or Scan Operation" are received.

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PLAY AUDIO Command

Table 74 - Commands That Will Stop a Play or Scan Operation
Opcode(s)

Command Description

A6h
4Bh
45h
47h
B4h
28h
A8h
BCh
44h
D5h
2Bh
DAh
1Bh

LOAD / UNLOAD CD
PAUSE/RESUME
PLAY AUDIO (10)
PLAY AUDIO MSF
PLAY CD
READ (10)
READ (12)
READ CD
READ HEADER
READ CD MSF
SEEK
SET CD-ROM SPEED
START/STOP UNIT

ATA commands other than A2, A0 will stop play or scan.
The CD-ROM drive should accept and perform the commands specified in "Table 74 - Commands That Will Stop a Play
or Scan Operation" without terminating an AUDIO PLAY command already in progress. See "Figure 15 - Stop Play/
Play Audio/Audio Scan/Pause/Resume Sequencing" on page 196 for additional information.

Table 75 - Commands That Will Not Stop a Play or Scan Operation
Opcode
ANY

Command Description

12h
BDh
55h

When it generates an Illegal Field in Command Packet CHECK CONDITION.
INQUIRY
MECHANISM STATUS
MODE SELECT

5Ah
1Eh
25h
42h

MODE SENSE
PREVENT/ALLOW MEDIA REMOVAL
READ CD-ROM CAPACITY
READ SUB-CHANNEL

43h

READ TOC

03h
D8h

REQUEST SENSE
SCAN

00h

TEST UNIT READY

working draft ATAPI

Action Taken
Will terminate normally
The Inquiry data will be returned
Will execute normally
The Mode Select will be accepted and executed as long as no
Media or Mode information is changed. If parameters that affect
the play are changed, the Mode Select will terminate with a
CHECK CONDITION without being executed.
Will execute normally
Will execute normally
Will execute normally
Only the current position information (Format Code 01h) will be
supported while the play is in progress. If any other type of information is requested the READ SUB-CHANNEL will not be executed and a CHECK CONDITION will be generated.
Only drives that cache the TOC will be able to respond to this command while the play is in progress. If the drive does not support
caching the TOC, the command will not be executed and a
CHECK CONDITION will be generated.
Will execute normally
SCAN command will be executed and the PLAY command will
resume at completion of the scan
Will execute normally

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ATAPI Packet Commands for CD-ROM devices
PLAY AUDIO MSF Command

10.8.9 PLAY AUDIO MSF Command
The PLAY AUDIO MSF command requests that the ATAPI CD-ROM Drive begin an audio playback operation. The
command function and the output of audio signals shall be as specified by the settings of the mode parameters including
the SOTC bit described on page 111.

Table 76 - PLAY AUDIO MSF Command
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

7

6

5

4

3

2

1

0

Operation Code (47h)
Reserved
Reserved
Starting M Field
Starting S Field
Starting F Field
Ending M Field
Ending S Field
Ending F Field
Reserved
Reserved
Reserved

This command responds with immediate status, allowing overlapped commands. This command shall set the DSC bit
upon command completion. See also "10.4 Immediate Command Processing Considerations" on page 90.
The Starting M field, the Starting S field, and the Starting F field specify the absolute MSF address at which the audio
play operation shall begin. The Ending M field, the Ending S field, and the Ending F field specify the absolute MSF address where the audio play operation shall end. All contiguous audio sectors between the starting and the ending MSF
address shall be played.
If the Starting Minutes, Seconds and Frame Fields are set to FFh, the Starting address is taken from the Current Optical
Head location. This allows the Audio Ending address to be changed without interrupting the current playback operation.
A Starting MSF address equal to an ending MSF address causes no audio play operation to occur. This shall not be considered an error. If the Starting MSF address is greater than the Ending MSF address, the command shall be terminated
with CHECK CONDITION status. The sense key shall be set to ILLEGAL REQUEST.
If the starting address is not found, if the address is not within an audio track, or if a not ready condition exists, the command shall be terminated with CHECK CONDITION status.
See "10.8.8.1 Play Audio with Immediate Packet Commands" on page 126 for information on overlapped commands
during an Audio Playback.

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ATAPI CD-ROM Specification
PLAY AUDIO MSF Command

Table 77 - Recommended Sense Key, ASC and ASCQ for Play Audio MSF Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
3A

00
01
02
03

02

06

00

03

02

05

21

05

63

05

64

working draft ATAPI

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED
LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

MEDIUM NOT PRESENT
NO REFERENCE POSITION FOUND (media may be upside down)
NO SEEK COMPLETE
LOGICAL BLOCK ADDRESS OUT OF RANGE
END OF USER AREA ENCOUNTERED ON THIS TRACK
ILLEGAL MODE FOR THIS TRACK OR INCOMPATIBLE MEDIUM

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ATAPI Packet Commands for CD-ROM devices
PLAY AUDIO MSF Command

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ATAPI CD-ROM Specification
PLAY CD Command
10.8.10 PLAY CD Command
The PLAY CD command provides one standard, universal way of sending digital CD data to an external device (e.g. an
IEC958 or EBU port).

Table 78 - PLAY CD Command (LBA Form)
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

7

6

5

4

3

2

Operation Code (BCh)
Expected Sector Type

Reserved

1

0

MSF (0)

Reserved

MSB
Starting Logical Block Address
LSB
MSB
Transfer Length in Blocks

SPEED

Reserved

Port 2
Reserved

Port 1

Composite

LSB
Audio

2

1

0

MSF (1)

Reserved

Composite

Audio

Table 79 - PLAY CD Command (MSF Form)
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

7

6

5

Reserved

SPEED

Reserved

4

3

Operation code (B4h)
Expected Sector Type
Reserved
Starting M Field
Starting S Field
Starting F Field
Ending M Field
Ending S Field
Ending F Field
Reserved
Port 2
Port 1
Reserved

The Expected Sector Type field is used to check the sector type only. If the Requested Sector(s) do not match the specified type, the command will be terminated with a CHECK CONDITION. The Sector that does not match will not be
transferred to output port. The sense key shall be set to ILLEGAL MODE FOR THIS TRACK.
Implementer’s Note: The Expected Sector Type is used to generate an error and terminate the transfer when the sectors
found on the media, do not match the type desired. This field has NO control of the actual number of bytes transferred.

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ATAPI Packet Commands for CD-ROM devices
PLAY CD Command

Table 80 - PLAY CD, Expected Sector Type Field Definition
Expected
Sector
Type

Definition

000b

Any Type
(Mandatory)

001b

CD DA
(Mandatory)
Mode 1
(Mandatory)

010b

011b

Mode 2
(Mandatory)

100b

Mode 2 Form 1
(Mandatory)
Mode 2 Form 2
(Mandatory)

101b

110b 111b

Description
No checking of the Sector Type will be performed. The device shall always terminate a command, at the sector where a transition between CD-Rom and CD-DA
occurs.
Only Red Book (CD-DA) sectors shall be allowed. An attempt to read any other
format shall result in the reporting of an error.
Only Yellow Book sectors which have a “user” data field of 2048 bytes shall be
allowed. An attempt to read any other format shall result in the reporting of an
error.
Only Yellow Book sectors which have a “user” data field of 2336 bytes shall be
allowed. An attempt to read any other format shall result in the reporting of an
error.
Only Green Book sectors which have a “user” data field of 2048 shall be allowed.
An attempt to read any other format shall result in the reporting of an error.
Only Green Book sectors which have a “user” data field of 2324 shall be allowed.
An attempt to read any other format shall result in the reporting of an error. Note
that the spare data is included in the user data making the size 2324+4= 2328.
Reserved

See also, CD-ROM Sector Formats on page 73.

Table 81 - PLAY CD, Field Definition
Flag
Audio
Composite
Port 1
Port 2
SPEED

Page 132

Value
0
1
0
1
0
1
0
1
0
1

Description
Analog Audio Channel is Disabled
Analog Audio Channel is Enabled
Composite Video port is Disabled
Composite Video port is Enabled
Digital Port 1 is Disabled
Digital Port 1 is Enabled
Digital Port 2 is Disabled
Digital Port 2 is Enabled
Speed will be set to x1 for the operation
The Speed used will be the best possible

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ATAPI CD-ROM Specification
PLAY CD Command

Table 82 - Recommended Sense Key, ASC and ASCQ for PLAY CD Command Errors
Sense
Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

03

02

05

21

05

64

05

00

0B

BF

working draft ATAPI

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00

11

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT
NO SEEK COMPLETE
LOGICAL BLOCK ADDRESS OUT OF RANGE
ILLEGAL MODE FOR THIS TRACK OR INCOMPATIBLE MEDIUM
PLAY OPERATION IN PROGRESS
LOSS OF STREAMING

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ATAPI Packet Commands for CD-ROM devices
PLAY CD Command

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ATAPI CD-ROM Specification
PREVENT/ALLOW MEDIUM REMOVAL Command
10.8.11 PREVENT/ALLOW MEDIUM REMOVAL Command
The PREVENT/ALLOW MEDIUM REMOVAL command requests that the ATAPI CD-ROM Drive enable or disable
the removal of the medium. The prevention of media removal (when implemented) shall be accomplished through the
use of a Locking Mechanism. The locking mechanism is optional and an error shall be returned if a command to prevent
medium removal is issued (Sense key 05 ILLEGAL REQUEST, Sense Code 24 INVALID FIELD IN COMMAND
PACKET).

Table 83 - PREVENT ALLOW MEDIUM REMOVAL Command
Bit
Byte

7

6

5

0
1
2
3
4
5
6
7
8
9
10
11

4

3

Operation Code (1Eh)
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved

2

1

0

Prevent

The prevention of medium removal shall begin when the Host Computer issues a PREVENT/ALLOW MEDIUM REMOVAL command with a prevent bit of one (medium removal prevented). The prevention of medium removal shall terminate:
1.

after the Host Computer has issued a PREVENT ALLOW MEDIUM REMOVAL command with a prevent bit of
zero (Unlock), and the ATAPI CD-ROM Drive has successfully performed a synchronize cache operation; or

2.

upon a hard RESET condition; or

3.

if the drive does not support a locking mechanism.

While a prevention of medium removal condition is in effect (Locked) the ATAPI CD-ROM Drive shall inhibit mechanisms that normally allow removal of the medium by an operator. This is also the case for changers.
The default state of the drive at power on is unlocked, unless the drive supports a prevent/allow jumper and the jumper is
in the prevent state (See "10.8.6.4 CD-ROM Capabilities and Mechanical Status Page" on page 118.)
This command will affect the actions of the START/STOP UNIT command (See "10.8.25 START/STOP UNIT Command" on page 197) and other mechanisms external to this specification (manual ejection / media removal systems.)

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ATAPI Packet Commands for CD-ROM devices
PREVENT/ALLOW MEDIUM REMOVAL Command

Table 84 - Actions for Lock / Unlock / Eject
Operation
Unlock
(Prevent = 0)
Lock
(Prevent = 1)
Lock when the
drive does not
support a Locking Mechanism
Eject
(START/STOP
UNIT command with LoEj
set)
Manual Eject

Locked /
Unlocked
Unlocked
Locked
Unlocked

If Drive Not Ready
(No Media)

If Drive Ready
(Media Present)

Locked
Would
always be
Unlocked

No Error
No Error, Now media may be inserted
No Error, Drive door locked and will not
allow media to be inserted
No Error
Error:
05 ILLEGAL REQUEST, 24 INVALID
FIELD IN COMMAND PACKET

No Error
No Error, Now media may be removed
No Error, Drive door locked and will not allow
media to be removed
No Error
Error:
05 ILLEGAL REQUEST, 24 INVALID
FIELD IN COMMAND PACKET

Unlocked

No Error and Tray is opened

Locked

Error:
02 Not ready, 53 Media Removal Prevented

No Error:
Media Ejects
Error:
02 Not ready, 53 Media Removal Prevented

Unlocked
Locked

Tray opens (If tray exists)
No operation occurs

Media is Ejected
No operation, Media stays locked in drive

Table 85 - Recommended Sense Key, ASC and ASCQ for Prevent/Allow Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
3A

00
01
02
03

02

53

02

Page 136

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED
LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

MEDIUM NOT PRESENT
MEDIA REMOVAL PREVENTED

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ATAPI CD-ROM Specification
READ (10) Command
10.8.12 READ (10) Command
The READ (10) command requests that the ATAPI CD-ROM Drive transfer data to the Host Computer. The most recent
data value written in the addressed logical block shall be returned.

Table 86 - READ (10) Command
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

7

6

5

4

3

2

1

0

Operation Code (28h)
Reserved
MSB
Logical Block Address
LSB
MSB

Reserved
Transfer Length
LSB
Reserved
Reserved
Reserved

The Transfer Length field specifies the number of contiguous logical blocks of data that shall be transferred. A transfer
length of zero indicates that no logical blocks shall be transferred. This condition shall not be considered an error. Any
other value indicates the number of logical blocks that shall be transferred.
Although the CD-ROM is capable of returning a variety of data, this command shall only return the “User Data” portion
of the sector. This field is always 2048 bytes in length for Mode 1 and Mode 2 Form 1 sectors, which are the only sector
types allowed. For all other sector types, the device shall set the ILI bit in the Request Sense Standard Data and return a
“ILLEGAL MODE FOR THIS TRACK” error if any read to them using this command is attempted.

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ATAPI Packet Commands for CD-ROM devices
READ (10) Command

Table 87 - Recommended Sense Key, ASC and ASCQ for READ (10) Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

03

02

05

21

05

64

03

11

05

03

11

06

01

17

01

01

18

01

01

18

04

Page 138

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT
NO SEEK COMPLETE
LOGICAL BLOCK ADDRESS OUT OF RANGE
ILLEGAL MODE FOR THIS TRACK OR INCOMPATIBLE MEDIUM
L-EC UNCORRECTABLE ERROR
CIRC UNRECOVERED ERROR
RECOVERED DATA WITH RETRIES
RECOVERED DATA WITH ERROR CORRECTION & RETRIES
APPLIED
RECOVERED DATA WITH L-EC

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ATAPI CD-ROM Specification
READ (12) Command
10.8.13 READ (12) Command
The READ (12) command requests that the ATAPI CD-ROM Drive transfer data to the Host Computer. The most recent
data value written in the addressed logical block shall be returned.

Table 88 - READ (12) Command
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

7

6

5

4

3

2

1

0

Operation Code (A8h)
Reserved
MSB
Logical Block Address
LSB
MSB
Transfer Length
LSB
Reserved
Reserved

The Transfer Length field specifies the number of contiguous logical blocks of data that shall be transferred. A transfer
length of zero indicates that no logical blocks shall be transferred. This condition shall not be considered an error. Any
other value indicates the number of logical blocks that shall be transferred.
Although the CD-ROM is capable of returning a variety of data, this command shall only return the “User Data” portion
of the sector. This field is always 2048 bytes in length for Mode 1 and Mode 2 Form 1 sectors, which are the only sector
types allowed. For all other sector types, the device shall set the ILI bit in the Request Sense Standard Data and return a
“ILLEGAL MODE FOR THIS TRACK” error if any read to them using this command is attempted.

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ATAPI Packet Commands for CD-ROM devices
READ (12) Command

Table 89 - Recommended Sense Key, ASC and ASCQ for READ (10) Command Errors
Sense
Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

03

02

05

21

05

64

03

11

05

03

11

06

01

17

01

01

18

01

01

18

04

Page 140

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT
NO SEEK COMPLETE
LOGICAL BLOCK ADDRESS OUT OF RANGE
ILLEGAL MODE FOR THIS TRACK OR INCOMPATIBLE MEDIUM
L-EC UNCORRECTABLE ERROR
CIRC UNRECOVERED ERROR
RECOVERED DATA WITH RETRIES
RECOVERED DATA WITH ERROR CORRECTION & RETRIES
APPLIED
RECOVERED DATA WITH L-EC

working draft ATAPI

ATAPI CD-ROM Specification
READ CD-ROM CAPACITY Command
10.8.14 READ CD-ROM CAPACITY Command
The READ CD-ROM CAPACITY command provides a means for the Host Computer to request information regarding
the capacity of the Device. The general function of the CD-ROM version of READ CAPACITY is the same but the exact
definition of the returned logical block address is modified to allow returning a possibly inexact value (but one with a
known error boundary) based on CD-ROM table of contents data. This error boundary occurs when the last track is an
audio track, and could cause the last block to be +/- 75 sectors from the actual end of the track. This error is a tolerance
in the addressing of Audio data built into the Media specifications for CD-ROM. For many CD-ROM devices, this implementation allows a quicker response.

Table 90 - READ CD-ROM CAPACITY Command
Bit
Byte

7

6

5

0
1
2
3
4
5
6
7
8
9
10
11

4

3

2

1

0

1

0

Operation code (25h)
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved

Eight bytes of READ CD-ROM CAPACITY data shall be returned to the Host Computer.

Table 91 - READ CAPACITY DATA
Bit
Byte
0
1
2
3
4
5
6
7

7

6

5

4

3

MSB

Logical Block Address

MSB

Block Length in Bytes
(Length reported shall be 2048d)

2

LSB

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LSB

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ATAPI Packet Commands for CD-ROM devices
READ CD-ROM CAPACITY Command

Table 92 - Recommended Sense Key, ASC and ASCQ for Read Capacity Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

Page 142

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT

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ATAPI CD-ROM Specification
READ CD Command
10.8.15 READ CD Command
The READ CD command (Family) provides one standard, universal way of accessing CD data. Rather than breaking the
types of data into several related commands, this command is generic to all CD data types.
This command returns any of the CD data streams, including the headers, EDC and ECC, ROM data and CD-DA data.
Each type of data is enabled via the use of flags. These flags indicate which information from the CD is to be returned in
the data stream. If a flag is cleared, then that particular information will not be returned. If all the flags are cleared, no
data will be returned to the host and this condition is not treated as an error.

Table 93 - READ CD Command
Bit
Byte
0
1
2
3
4
5
6
7
8
9

7

6

5

4

3

2

1

Operation Code (BEh)
Expected Sector Type
Starting Logical Block Address

Reserved
MSB

0

Reserved

LSB
MSB

Transfer Length in Blocks

Synch
Field

Flag Bits
User Data
EDC &
ECC

LSB

10
11

Header(s) Code
Reserved

Error Flag(s)

Reserved

Sub-Channel Data Selection Bits
Reserved

The Expected Sector Type field is used to limit the amount of information returned to the Host. If the Requested Sector(s)
do not match the specified type, the command will be terminated with a CHECK CONDITION. The Sector that does not
match will not be transferred to the Host. The sense key shall be set to ILLEGAL MODE FOR THIS TRACK.
Implementer’s Note: The Expected Sector Type is used to generate an error and terminate the transfer when the sectors
found on the media, do not match the type desired. This field has NO control of the actual number of bytes transferred.

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ATAPI Packet Commands for CD-ROM devices
READ CD Command

Table 94 - READ-CD, Expected Sector Type Field Definition
Expected
Sector
Type

Definition

000b

Any Type
(Mandatory)

001b

CD DA
(Optional)
Mode 1
(Mandatory)

010b

011b

Mode 2
(Mandatory)

100b

Mode 2 Form 1
(Mandatory)
Mode 2 Form 2
(Mandatory)

101b

110b 111b

Description
No checking of the Sector Type will be performed. The device shall always terminate a command, at the sector where a transition between CD-Rom and CD-DA
occurs.
Only Red Book (CD-DA) sectors shall be allowed. An attempt to read any other
format shall result in the reporting of an error.
Only Yellow Book sectors which have a “user” data field of 2048 bytes shall be
allowed. An attempt to read any other format shall result in the reporting of an
error.
Only Yellow Book sectors which have a “user” data field of 2336 bytes shall be
allowed. An attempt to read any other format shall result in the reporting of an
error.
Only Green Book sectors which have a “user” data field of 2048 shall be allowed.
An attempt to read any other format shall result in the reporting of an error.
Only Green Book sectors which have a “user” data field of 2324 shall be allowed.
An attempt to read any other format shall result in the reporting of an error. Note
that the spare data is included in the user data making the size 2324+4= 2328.
Reserved

See also, CD-ROM Sector Formats on page 73.

The Synch Field Bit, when set to one indicates that the Synch Field from the sector will be included in the data stream.
Note that the data fields that are requested to be included in the data stream shall be contiguous. The Synch Field information (if selected) will be the first information in the data stream; all other fields will follow.
The Header(s) Code is an encoded field that indicates the Header / Subheader information to be placed in the data stream.

Table 95 - READ CD, Header(s) Code Field Definition
Header(s)
Code
00b
01b
10b
11b

Definition
None
HdrOnly
SubheaderOnly

All Headers

Description
None of the header data shall be placed in the data stream.
Only the Mode 1 or Form 1 4-byte header will be returned in the data stream.
Only the Mode 2 Form 1 or 2 Subheader will be placed into the data stream.
Both the Header and Subheader will be placed in the data stream.

The User Data Flag, when set to one, indicates that the Data part of a CD Sector shall be returned in the data stream.
When set to 1, the whole user data will be returned to the host. Note that the setting of the Mode Select Density Code
does not apply to this command, and the physical user data will be returned. If the current track is an Audio Track then
the Audio Data will be returned, else the normal CD-ROM data will be returned. The possible data lengths are 2048,
2336, 2328 and 2352.
The EDC and ECC Flag, when set to one, indicates that the EDC and ECC (L-EC) field shall be included in the data

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ATAPI CD-ROM Specification
READ CD Command
stream. For Mode 1 CDs this will include the 8 bytes of pad data.
Error Flag(s) is an encoded field that indicates which (if any) of the C2 and/or Block Error data will be included in the
data stream. All the field types are mandatory. If the drive does not support the C2 pointers (as reported in the Mode
sense Capabilities page) the data returned shall be zero filled.

Table 96 - READ CD, Error Flag(s) Field Definition
Error
Flags

Definition

00b
01b

None
C2 Error Flag data

10b

C2 & Block Error Flags

11b

Reserved

Description
No Error information will be included in the data stream.
The C2 Error Flag (Pointer) bits (2352 bits or 294 bytes) will be included in the data
stream. When the C2 Error pointer bits are included in the data stream, there will be
one bit for each byte in error in the sector (2352 total). The bit ordering is from the
most significant bit to the least significant bit in each byte. The first bytes in the sector
will be the first bits/bytes in the data stream.
Both the C2 Error Flags (2352 bits or 294 bytes) and the Block Error Byte will be
included in the data stream. The Block Error byte is the OR of all the C2 Error Flag
bytes. So that the data stream will always be an even number of bytes, the Block Error
byte will be padded with a byte (undefined). The Block Error byte will be first in the
data stream followed by the pad byte.
Reserved for future enhancement.

The Sub-Channel Data Selection bits indicate which CD Sub-Channel information is to be included in the data stream,
the Q information and/or the “Raw” Sub-channel information (All eight channels, one byte from each of the small
frames.) If the bit is set, then that Sub-channel data will be included in the data stream to the Host.

Table 97 - READ CD, Sub-channel Data Selection Field Definition
Sub-channel
Data
Selection
000b
001b
010b
011b
100b
101b - 111b

Definition
No Sub-channel Data
RAW
Q
Reserved
R-W
Reserved

Description

Type

No Sub-channel data will be transferred
Raw Sub-channel data will be transferred
Q data will be transferred

Mandatory
Optional
Optional

R-W data will be transferred

Optional

Support of Sub-channel data is optional. In the case of R-W the drive may return the data de-interleaved and error-corrected, RAW or padded with zeros depending on the R-W Supported and R-W de-interleaved and error-corrected bits in
the CD-ROM capabilities and mechanical status page. Changing the DCR bit using Mode Select for page 1 (Read error
recovery page) will affect error correction of subcode data. The inclusion of the sub-channel data will only be valid for
Audio sectors.
If the Starting Logical Block Address is set to FFFFFFFFh and the only information requested to be placed in the data
stream is the Sub-channel data and there is currently a PLAY AUDIO command in process, the actual address used will
be from the current location (of the Play). If the drive is not playing audio, the drive will respond with a CHECK CONDITION with a sense key/ASC/ASCQ of 05h/B9h/00h (Play Not in Progress).

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ATAPI Packet Commands for CD-ROM devices
READ CD Command

Table 98 - Formatted Q-subcode Data (A Total of 16 Bytes)
Byte
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

Description
Control (4 M.S. bits), ADR (4 L.S. bits)
Track number
Index number
Min
Sec
Frame
Reserved (00h)
AMin
Asec
AFrame
CRC* or 00h (hex)
CRC* or 00h (hex)
00h (pad)
00h (pad)
00h (pad)
00h (pad)

* CRC is optional

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READ CD Command
Table 99 - Number of Bytes Returned Based on Data Selection Field
Data to be transferred
User Data
User Data + EDC/ECC
Header Only
Header Only + EDC/ECC
Header & User Data
Header & User Data + EDC/ECC
Sub Header Only
Sub Header Only + EDC/ECC
Sub Header & User Data
Sub Header & User Data + EDC/ECC
All Headers Only
All Headers Only + EDC/ECC
All Headers & User Data
All Headers & User Data + EDC/ECC
Sync & User Data
Sync & User Data + EDC/ECC
Sync & Header Only
Sync & Header Only + EDC/ECC
Sync & Header & User Data
Sync & Header & User Data + EDC/ECC
Sync & Sub Header Only
Sync & Sub Header Only + EDC/ECC
Sync & Sub Header & User Data
Sync & Sub Header & User Data + EDC/ECC
Sync & All Headers Only
Sync & All Headers Only + EDC/ECC
Sync & All Headers & User Data
Sync & All Headers & User Data + EDC/ECC
Repeat All Above and Add
Error Flags
Repeat All Above and Add
Block & Error Flags

Flag
Bits

CD-DA

Mode 1

Mode 2
non XA

Mode 2
Form 1

Mode 2
Form 2

10h
18h
20h
28h
30h
38h
40h
48h
50h
58h
60h
68h
70h
78h
90h
98h
A0h
A8h
B0h
B8h
C0h
C8h
D0h
D8h
E0h
E8h
F0h
F8h
02h

2352
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
(10h)
294

2048
2336
4
Illegal
2052
2344
8
Illegal
(10h)
(10h)
12
Illegal
(30h)
(30h)
Illegal
Illegal
16
Illegal
2064
2344
Illegal
Illegal
(10h)
(10h)
24
Illegal
2064
2352
294

2336
(10h)
4
Illegal
2340
(30h)
8
Illegal
(10h)
(10h)
12
Illegal
(30h)
(30h)
Illegal
Illegal
16
Illegal
2352
(30h)
Illegal
Illegal
(10h)
(10h)
24
Illegal
2352
(F0h)
294

2048
2336
4
Illegal
Illegal
Illegal
8
Illegal
2056
2344
12
Illegal
2060
2340
Illegal
Illegal
16
Illegal
Illegal
Illegal
Illegal
Illegal
Illegal
Illegal
24
Illegal
2072
2352
294

2328
(10h)
4
Illegal
Illegal
Illegal
8
Illegal
2336
(50h)
12
Illegal
2340
2340
Illegal
Illegal
16
Illegal
Illegal
Illegal
Illegal
Illegal
Illegal
Illegal
24
Illegal
2352
(F0h)
294

04h

296

296

296

296

296

The lengths of the data returned from the READ CD command vary based on the type of sector that is being read and
the requested fields to be returned to the Host. Many combinations are possible, but most are not very useful. Table 99,
“Number of Bytes Returned Based on Data Selection Field,” on page 147 specifies how the drive responds to many of the
requests possible. Requests for transfers not specified by this table shall not be supported and treated as Illegal. Illegal
values will cause the command to be aborted with a CHECK Condition, Sense Key 05, ASC 24 (INVALID FIELD IN
COMMAND PACKET).
The Values in () indicate that the amount of data is the same as the Flag byte setting specified by the contents of the parenthesis.
Values that are shaded are most useful to the host and shall return the number of bytes specified if supported.
See "Figure 11 - CD-ROM Sector Formats" on page 73 for a description of the data available for each sector type.

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ATAPI Packet Commands for CD-ROM devices
READ CD Command

Table 100 - Recommended Sense Key, ASC and ASCQ for Read CD Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

03

02

05

21

05

64

05

00

0B

BF

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ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00

11

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT
NO SEEK COMPLETE
LOGICAL BLOCK ADDRESS OUT OF RANGE
ILLEGAL MODE FOR THIS TRACK OR INCOMPATIBLE MEDIUM
PLAY OPERATION IN PROGRESS
LOSS OF STREAMING

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ATAPI CD-ROM Specification
READ CD Command

The CD-DA audio data includes 16 bits of information for each channel, and will be formatted as follows when an audio
track is read.

Table 101 - CD-DA (Digital Audio) Data Block Format
Bit
Byte

7

6

5

0
b7

b6

b5

b15

b14

b13

b7

b6

b5

b15

b14

b13

1
2
3

4

3

Cell 1 (1st of 588)
Left Channel (Lower Byte)
b4
b3
Left Channel Upper Byte
b12
b11
Right Channel (Lower Byte)
b4
b3
Right Channel Upper Byte
b12
b11

2

1

0

b2

b1

b0

b10

b9

b8

b2

b1

b0

b10

b9

b8

b2

b1

b0

b10

b9

b8

b2

b1

b0

b10

b9

b8

.
.
.
2348
b7

b6

b5

b15

b14

b13

b7

b6

b5

b15

b14

b13

2349
2350
2351

Left Channel (Lower Byte)
b4
b3
Left Channel Upper Byte
b12
b11
Right Channel (Lower Byte)
b4
b3
Right Channel Upper Byte
b12
b11

If the CD-ROM Drive does not support the CD-DA Stream-Is-Accurate capability (See "10.8.6.4 CD-ROM Capabilities
and Mechanical Status Page" on page 118) then the Digital Audio data must be read as a continuous stream. If while
streaming the drive must stop, there will be a non-recoverable error generated (Sense Key 0Bh ABORTED Command,
Sense Code BFh LOSS OF STREAMING). This is due to the 1 second uncertainty of the address (There is no header in
CD-DA Data). Reissuing the command may not return exactly the same data as the previous try. When the drive supports the Stream Accurate capability, there will be no error, only some time delay for rotational latency.

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ATAPI Packet Commands for CD-ROM devices
READ CD Command

Data

Sync Header

EDC

ECC
(P&Q)

C2 Error Flags
Block Error Flags

SubHeader

SmallFrame(1)

SmallFrame(98)

CD Digital Audio

C2 Error Flags
Block Error Flags
SmallFrame(1)

SmallFrame(98)

Raw Sub-channel

CD Digital Audio

C2 Error Flags
Block Error Flags
SmallFrame(1)

SmallFrame(98)

Q-Formatted

CD Digital Audio

C2 Error Flags
Block Error Flags
SmallFrame(1)

SmallFrame(98)

R-W de-interleaved and
error-corrected

CD Digital Audio

C2 Error Flags
Block Error Flags

Figure 13 - Read CD Data Stream Order

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ATAPI CD-ROM Specification
READ CD Command
10.8.15.1 Description of Sub-channels R-W
Sync
Sync
p Q R-W

98 Bytes

.
.
.

96 Bytes (RAW)

p Q R-W
96 six-bit symbols
12Q

4 pad

Formatted Q

Sec. 5.1.6 Red Book

(How to cook Packet Data)

PACKET
Synch

2

PACKET
Synch

4 Groups of 24 words

24

24

PACK PACK

24

24

PACK

PACK

2

1

2

24

24

PACK PACK

Mode & EDC/ECC User Data
Item
Parity Q0/1

1

4 Groups of 24 words

16

24

24

PACK

PACK

EDC/ECC
Parity P0-P3

4

Instruction

Note: the sizes shown are in 6 bit words.

Figure 14 - Read CD Sub-channel, R-W (100b)

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ATAPI Packet Commands for CD-ROM devices
READ CD Command

Table 102 - R-W Raw
Bit
Byte

7

6

5

4

0
1
...
95

3

2

1

0

P2W (0)
P2W (1)
...
P2W (95)

R-W Raw is returned in the format and order found on the media. It is the responsibility of the device driver to deinterleave and perform error detection and correction on the RAW data to make it usable to higher level applications.

Table 103 - R-W De-Interleaved & Error Corrected
Bit
Byte
0
1
...
23
24
25
...
47
48
49
...
71
72
73
...
95

7

6

P
P

Q
Q

P
P
P

Q
Q
Q

P
P
P

Q
Q
Q

P
P
P

Q
Q
Q

P

Q

5

4

3

2

1

0

PACK1(0)
PACK1(1)
...
PACK1(23)
PACK2(0)
PACK2(1)
...
PACK2(23)
PACK3(0)
PACK3(1)
...
PACK3(23)
PACK4(0)
PACK4(1)
...
PACK4(23)

Drives that can not return P or Q code with PACK data will return 0 in the unsupported P or Q bits. Each PACK is generated after 2 contiguous Sub Channel data frames consisting of 24 bytes with 6 bits of PACK data per byte.Each 96 byte
Packet consists of 4 PACKs of 24 bytes each.
The basic RAW format is shown in "Figure 14 - Read CD Sub-channel, R-W (100b)" on page 151. The data is synchronized with the subcode synch patterns S0 and S1. Each group of 6 bits (R-W) is called a “symbol”. The symbol following
the synchs S0 and S1 is the first symbol of the first pack in a packet. The packs following the sync bytes in R~W data
must be from the same block and in chronological order.
To guard the data in the subcoding channels R-W, a (24,20) Reed-Solomon Error Correction Code is used. To improve
the burst error correction capability, eight-way interleaving is added to this error correction system.
The first two symbols in a pack have additional protection with a (4,2) Read-Solomon Error Correction Code. The first
symbol of a pack contains a mode-switch of 3 bits and a 3-bit subdivision of mode, called “item”. The defined mode-item

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ATAPI CD-ROM Specification
READ CD Command
combinations are defined in the following table.

Table 104 - Sub-channel R-W, Allowed Mode/Item Combinations
Mode

Item

000b (0d)
001b (1d)

000b (0d)
000b (0d)
001b (1d)
111b (7d)
000b (0d)
All Others

Description
The ZERO mode
The LINE GRAPHICS mode
The TV GRAPHICS mode
The USER mode
Reserved for future use

The R-W information is returned as part of the “raw” sub-channel data. The lower 6 bits of each of the bytes contain the
R-W data. This data follows the format shown in "Figure 14 - Read CD Sub-channel, R-W (100b)" on page 151. If the Q
information needs to be taken from the raw data, then it shall be deinterleaved according the Red book formats.

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READ CD Command

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ATAPI CD-ROM Specification
READ CD MSF Command
10.8.16 READ CD MSF Command
The READ CD command (Family) provides one standard, universal way of accessing CD data. Rather than breaking the
types of data into several related commands, this command is generic to all CD data types.
This command returns any of the CD data streams, including the headers, EDC and ECC, ROM data and CD-DA data.
Each type of data is enabled via the use of flags. These flags indicate which information from the CD is to be returned in
the data stream. If a flag is cleared, then that particular information will not be returned. If all the flags are cleared, no
data will be returned to the host and this condition is not treated as an error.

Table 105 - READ CD MSF Command
Bit
Byte

7

0
1
2
3
4
5
6
7
8
9

6

5

Reserved

Synch
Field
10
11

Header(s) Code
Reserved

4

3

2

1

0

Operation code (B9h)
Expected Sector Type
Reserved
Reserved
Starting M Field
Starting S Field
Starting F Field
Ending M Field
Ending S Field
Ending F Field
Flag Bits
User Data
EDC &
Error flag(s)
Reserved
ECC
Sub-Channel Data Selection Bits
Reserved

The Starting M field, the Starting S field, and the Starting F field specify the absolute MSF address at which the Read operation shall begin. The Ending M field, the Ending S field, and the Ending F field specify the absolute MSF address
where the Read operation shall end. All contiguous sectors between the starting and the ending MSF address shall be
read.
A starting MSF address equal to an ending MSF address prevents a read operation. This shall not be considered an error.
If the starting MSF address is greater than the ending MSF address, the command shall be terminated with CHECK
CONDITION status. The sense key shall be set to ILLEGAL REQUEST.
If the starting address is not found, or if a not ready condition exists, the command shall be terminated with CHECK
CONDITION status.
See "10.8.15 READ CD Command" on page 143 for a description of Expected User Data Type, Flag Bits and Sub-channel Data Selection Bits.

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ATAPI Packet Commands for CD-ROM devices
READ CD MSF Command

Table 106 - Recommended Sense Key, ASC and ASCQ for Read CD MSF Command Errors
Sense
Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

03

02

05

21

05

64

05

00

0B

BF

Page 156

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00

11

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT
NO SEEK COMPLETE
LOGICAL BLOCK ADDRESS OUT OF RANGE
ILLEGAL MODE FOR THIS TRACK OR INCOMPATIBLE MEDIUM
PLAY OPERATION IN PROGRESS
LOSS OF STREAMING

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ATAPI CD-ROM Specification
READ HEADER Command
10.8.17 READ HEADER Command
The READ HEADER command requests that the device return the CD-ROM Data Block Address Header of the requested logical block.

Table 107 - READ HEADER Command
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

7

6

5

4

3

2

Operation code (44h)
Reserved
Logical Block Address

MSB

1

0

MSF

Reserved

LSB
Reserved
Allocation Length

MSB

LSB
Reserved
Reserved
Reserved

See "8.6 CD-ROM Address Reporting Formats (MSF bit)" on page 78 for a description of the MSF bit.
The Logical Block Address field specifies the logical block at which the read header operation shall begin.
See the READ (10) command for exception handling.
The READ HEADER data format below defines the format for the returned CD-ROM data block address header of the
requested logical block.

Table 108 - READ HEADER LBA Data Format
Bit
Byte
0
1
2
3
4
5
6
7

7

MSB

working draft ATAPI

6

5

4

3

2

1

0

CD-ROM Data Mode
Reserved
Reserved
Reserved
Absolute CD-ROM Address

LSB

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ATAPI Packet Commands for CD-ROM devices
READ HEADER Command

Table 109 - READ HEADER MSF Data Format
Bit
Byte

7

6

5

4

3

2

1

0

CD-ROM Data Mode
0

0

ADR

1
2
3
4
5
6
7

Reserved
Reserved
Reserved
Reserved
M
S
F

The CD-ROM Data Mode field specifies the CD-ROM data mode of the logical blocks in this sector of data. The values
in this field are defined in "Table 110 - CD-ROM Data Mode Codes" on page 158.

Table 110 - CD-ROM Data Mode Codes
CD-ROM Data Mode
00h
01h
02h
03h - FFh

User Data Field Contents
(2048 Bytes)
All bytes zero
User data
User data
Reserved

Auxiliary Field Contents
(288 bytes)
All bytes zero
L-EC symbols
User data
Reserved

If the MSF bit is zero, the Absolute Address field gives the logical block address of the first logical block in the physical
sector where the data for the requested logical block address is found. If the MSF bit is one, the Absolute Address field
gives the MSF address of the sector where the data for the requested logical block address is found.

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READ HEADER Command
Table 111 - Recommended Sense Key, ASC and ASCQ for Read Header Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

03

02

05

21

05

64

working draft ATAPI

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT
NO SEEK COMPLETE
LOGICAL BLOCK ADDRESS OUT OF RANGE
ILLEGAL MODE FOR THIS TRACK OR INCOMPATIBLE MEDIUM

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READ HEADER Command

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ATAPI CD-ROM Specification
READ SUB-CHANNEL Command
10.8.18 READ SUB-CHANNEL Command
The READ SUB-CHANNEL command requests that the ATAPI CD-ROM Drive return the requested sub-channel data
plus the state of play operations.

Table 112 - READ SUB-CHANNEL Command
Bit
Byte

7

6

5

0
1

4

3

2

Operation code (42h)
Reserved

1

0

MSF

Reserved

(Mandatory)

2

Reserved

SubQ

Reserved

(Mandatory)

3
4
5
6
7
8
9
10
11

Sub-channel Data Format
Reserved
Reserved
Track Number
Allocation Length

MSB

LSB
Reserved
Reserved
Reserved

Sub-channel data returned by this command may be from the last appropriate sector encountered by a current or previous media accessing operation. When there is no current play operation, the ATAPI CD-ROM Drive may access the media to read the sub-channel data. The ATAPI CD-ROM Drive is responsible for ensuring that the data returned are
current and consistent.
See "8.6 CD-ROM Address Reporting Formats (MSF bit)" on page 78 for a description of the MSF bit. Support for the
MSF bit is mandatory.
The sub Q bit set to one requests that the ATAPI CD-ROM Drive return the Q sub-channel data. The sub Q bit set to zero
requests that no sub-channel data be returned. This shall not be considered an error. Support for the SubQ bit is mandatory. When the sub Q bit is Zero, only the Sub-Channel data header is returned.

Table 113 - Sub-channel Data Header Format
Bit
Byte

7

6

5

4

3

2

1

0

Sub Channel Data Header
0
1
2
3

Reserved
Audio Status
Sub-channel Data Length

The sub-channel data format field specifies the returned sub channel data. If this field is 01h, 02h or 03h, the requested
sub-Q data item is returned.

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ATAPI Packet Commands for CD-ROM devices
READ SUB-CHANNEL Command

Table 114 - Sub-channel Data Format Codes
Format Code

Support
Requirement

Returned data

00h
01h
02h
03h
04h - EFh
F0h - FFh

Reserved
CD-ROM current position
Media catalogue number (UPC/bar code)
Track international standard recording code (ISRC)
Reserved
Vendor-specific

Reserved
Mandatory
Mandatory
Mandatory
Optional

The track number field specifies the track number from which the ISRC code is transferred. This field shall have a value
from 01h to 63h (99d), and is valid only when the sub-channel data format is 03h. If this field is nonzero for all sub-channel data formats other than 03h the drive will terminate the command with a check condition (INVALID REQUEST / INVALID FIELD IN COMMAND PACKET).

10.8.18.1 CD-ROM Current Position Data Format

Table 115 - CD-ROM Current Position Data Format (Format Code 01h)
Bit
Byte

7

6

5

4

3

2

1

0

Sub Channel Data Header
0
1
2
3

Reserved
Audio Status
Sub-channel Data Length

MSB

LSB

CD-ROM Current Position Data Block
4
5
6
7
8
9
10
11
12
13
14
15

Sub Channel Data Format Code (01h)
ADR

MSB

Control
Track Number
Index Number
Absolute CD-ROM Address
See "Table 27 - MSF Address Format" on page 78
LSB

MSB

Track Relative CD-ROM Address

LSB

The Audio Status field indicates the status of play operations. The audio status values are defined in "Table 116 - Audio
Status Codes" on page 163. Audio status values 13h and 14h return information on previous audio operations; they are
returned only once after the condition has occurred. If another play operation is not requested, the audio status returned
for subsequent READ SUB-CHANNEL commands is 15h.

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READ SUB-CHANNEL Command

Table 116 - Audio Status Codes
Status
00h
11h
12h
13h
14h
15h

Description
Audio status byte not supported or not valid
Play operation in progress
Play operation paused
Play operation successfully completed
Play operation stopped due to error
No current audio status to return

The Sub-channel Data Length specifies the length in bytes of the following sub-channel data block. A sub-channel data
length of zero indicates that no sub-channel data block is included in the returned data. Sub-channel data length does not
include the sub channel header.
The Sub-Q Channel Data Block consists of control data (bytes 4 - 5), current position data (bytes 6 - 15) and identification data (bytes 16 - 47). The control data and current position data is obtained from the Q sub-channel information of the
current block. Identification data may be reported that was obtained from a previous block. If identification data is reported, the data shall be valid for the sector addressed by the current position data.
1.

If an play operation is proceeding in the background, position data for the last sector played shall be reported.

2.

In other cases, for instance after a READ command, the ATAPI CD-ROM Drive may either report position data
for the last sector processed for that operation or may report position data from the sector at the current read head
position.

The ADR field gives the type of information encoded in the Q sub-channel of this block, as shown in the following table.

Table 117 - ADR Sub-channel Q Field
ADR code
0h
1h
2h
3h
4h - Fh

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Description
Sub-channel Q mode information not supplied
Sub-channel Q encodes current position data (i.e. track, index, absolute address, relative address)
Sub-channel Q encodes media catalogue number
Sub-channel Q encodes ISRC
Reserved

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READ SUB-CHANNEL Command

Table 118 - Sub-channel Q Control Bits
Bit
0
1
2
3

Equals zero
Audio without pre-emphasis
Digital copy prohibited
Audio track
Two-channel audio

Equals one
Audio with pre-emphasis
Digital copy permitted
Data track
Four-channel audio

The Track Number field specifies the track from which ISRC data is read. This field must have a value between 01h and
63h and is valid only when the sub-channel data format field is 03h. In this case, the ATAPI CD-ROM Drive returns
ISRC data for this track.
The Index Number specifies the index number in the current track.
The Absolute CD-ROM Address field gives the current location relative to the logical beginning of the media. If the
MSF bit is zero, this field is a logical block address. If the MSF bit is one, this field is an absolute MSF address.
The Track Relative CD-ROM Address field gives the current location relative to the logical beginning of the current
track. If the MSF bit is zero, this field is a track relative logical block address. (If the current block is in the pre-gap area
of a track, this will be a negative value, expressed as a twos-complement number.) If the MSF bit is one, this field is the
relative MSF address from the Q sub-channel.

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10.8.18.2 Media Catalogue Number Data Format
A Media Catalogue Valid (MCVal) bit of one indicates that the media catalogue number field is valid. A MCVal bit of
zero indicates that the media catalogue number field is not valid.
The Media Catalogue Number field contains the identifying number of this media according to the uniform product code
values (UPC/EAN bar coding) expressed in ASCII. Non-zero values in this field are controlled by the Uniform Product
Code Council1) and the European Article Number Council2. A value in this field of all ASCII zeros indicates that the media catalog number is not supplied.
If media catalogue number data is found, the MCVal bit is set to one. If MCN data is not detected, the MCVal bit is set
to zero to indicate the Media Catalogue Number field is invalid.
Media catalogue number data returned by this command with sub-channel data format field code 02h may be from any
block that has UPC bar code Q sub-channel data. (This code is constant anywhere in every applicable disc.)
The CD-ROM Drive may either return the UPC information that it has previously read (Cached data) or may scan for the
information. As the UPC is only guaranteed to be contained in 1 out of 100 sectors and errors may be encountered, the
time required to return the UPC data could be several seconds.

Table 119 - Media Catalogue Number Data Format (Format Code 02h)
Bit
Byte

7

6

5

4

3

2

1

0

Sub Channel Data Header
0
1
2
3

MSB

Reserved
Audio Status
Sub-channel Data Length
LSB

Media Catalogue Number Data Block
4
5
6
7
8
9
23

MCVal

Sub Channel Data Format Code (02h)
Reserved
Reserved
Reserved
Reserved
Media Catalogue Number (UPC/Bar Code)
(See "Table 120 - UPC Format" on page 166)

1. The Uniform Product Code Council is located at 8163 Old Yankee Road, Suite J, Dayton, Ohio 45459.
2. The European Article Number Council is located at Rue des Colonies, 54-BTE8, 1000 Brussels, Belgium.

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Table 120 - UPC Format
Bit
Byte
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23

7

6

5

MCVal

4

3

2

1

0

Reserved
N1 (Most significant)
N2
N3
N4
N5
N6
N7
N8
N9
N10
N11
N12
N13
Zero
AFrame (Binary)

N1 through N13 shall be retrieved from the Q channel in mode 2. The data shall be encoded as ASCII characters (i.e. if
N1 of the UPC is 01bcd, then N1 of the above field shall be 49d or 31h).

10.8.18.3 Track International Standard Recording Code Data Format
The Track ISRC field contains the identifying number of this media according to the ISRC standards (DIN-31-621).

Table 121 - Track International Standard Recording Code Data Format
Bit
Byte

7

6

5

4

3

2

1

0

Sub Channel Data Header
0
1
2
3

Reserved
Audio Status
Sub-channel Data Length

Track ISRC Data Block
4
5
6
7
8
9
23

Page 166

Sub Channel Data Format Code (03h)
ADR (03)

TCVal

Control

Reserved
Reserved
Reserved
Track International Standard Recording Code (ISRC)

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ATAPI CD-ROM Specification
READ SUB-CHANNEL Command
If ISRC data is detected, the TCVal bit is set to one. If ISRC data is not detected, the TCVal bit is set to zero to indicate
the ISRC field is invalid.
Track ISRC data returned by this command with sub-channel data format field 03h may be from any block in the specified track that has ISRC data. When ADR field is 3 (0011), it is used to assign a unique number to an audio track. This is
done by means of the ISRC which is 12 characters long (represented by I1 to I12.) The ISRC can only change immediately after the TNO has been changed.

Table 122 - Raw ISRC Format on the CD-ROM Disc
S0,
S1

Control

ADR

I1 I2

I3 I4 I5

3

00:
zero:

00

I6 I7 I8 I9 I10 I11 I12

zero

A Frame

CRC

ISRC 60 bits

These 2 bits are zero.
These 4 bits are zero.

I1, I2 are the country code; I3, I4, I5 are the owner code; I6, I7 are the year of recording; I8, I9, I10, I11, I12 are the serial number of the recording. AFrame is the absolute frame number.
Note: The information returned for the ISRC may be returned as is from the media, or in some cases it may be converted
to ASCII. It is recommeded that the drive convert the information to ASCII.

Table 123 - ISRC Format of Data Returned to Host
Bit
Byte
8
9
10
11
12
13

7

6

5

TCVal

4

3

working draft ATAPI

1

0

Reserved
I1 (Country Code)
I2
I3 (Owner Code)
I4
I5

Note: The shaded Bits are used if the
drive converts the data returned to ASCII

14
15
16
17
18
19
20
21
22
23

2

I6 (Year of Recording)
I7
I8 (Serial Number)
I9
I10
I11
I12
Zero
AFrame
Reserved

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Table 124 - Recommended Sense Key, ASC and ASCQ for Read Sub-channel Command Errors
Sense Key

ASC

ASCQ

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

03

02

05

21

05

64

05

00

11

05

00

12

05

00

13

05

00

14

05

00

15

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT
NO SEEK COMPLETE
LOGICAL BLOCK ADDRESS OUT OF RANGE
ILLEGAL MODE FOR THIS TRACK OR INCOMPATIBLE MEDIUM
PLAY OPERATION IN PROGRESS
PLAY OPERATION PAUSED
PLAY OPERATION SUCCESSFULLY COMPLETED
PLAY OPERATION STOPPED DUE TO ERROR
NO CURRENT AUDIO STATUS TO RETURN

10.8.18.4 Caching of Sub-Channel Data
Sub-channel Q data shall be cached by the drive while playing audio. This is necessary so that the Read Sub-channel or
Read CD commands can access the Sub-Channel Q data while executing an immediate command. The device shall generate an error if the data is not in the cache.
Read Sub-channel will return the “Current” data, while Read CD will will return the specified data and remove any previous (older) data from the cache.
Using “FFFFFFFF” on Read CD will work just like Read Sub-channel.

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READ TOC Command
10.8.19 READ TOC Command
The READ TOC command requests that the ATAPI CD-ROM Drive transfer data from the table of contents to the Host
Computer. Some drives will cache the TOC data and will be able to return it during an Play command. Drives that do not
cache the data will generate an error and not complete the command.

Table 125 - READ TOC Command
Bit
Byte

7

6

0
1

5

4

3

2

Operation code (43h)
Reserved

1

0

MSF

Reserved

(Mandatory)

2
3
4
5
6
7
8
9
10
11

Reserved

Format
Reserved
Reserved
Reserved
Starting Track / Session Number
Allocation Length

MSB

LSB
Format

Reserved
Reserved
Reserved

See "8.6 CD-ROM Address Reporting Formats (MSF bit)" on page 78 for a description of the MSF bit. Support for the
MSF bit is mandatory.
To identify the multi-session CD TOC, the most significant 2 bits of the byte at offset 9 (Format) have been assigned to
identify this information. For handling multi-session and/or the Kodak PhotoCD, format 01b can be used. For drives that
do not support multi-session, the First session number should be equal to the Last session number in the returned TOC
information. Format field definition: When Format in Byte 2 is zero, then Byte 9 is used. Other values for this field are
reserved for definition in MMC.
Note: The Format field in Byte 9 is a vendor-specific area and will be removed in subsequent versions of this specification. Functionality is moving to Byte 2.
00b Mandatory

This mode is a backward compatible mode where the starting track field specifies the starting track number for which the data shall be returned. If this value is zero, the table of contents data shall begin with the first track on the
medium. The data are returned in contiguous ascending track number order.

01b Mandatory

Multi-session mode and returns the first session number, last session number
and last session address. In this format the Starting Track is reserved.

10b Mandatory

Returns all Sub-channel Q data in the lead in (TOC) area, starting from a specified session number as specified in the Session Number Field. In this mode,
the drive will support Q Subcode Point field values of A0h, A1h, A2h; Track
Numbers of B0h, B1h, B2h, B3h, B4h and C0h.

11b

Reserved

The Starting Track Field specifies the starting track number for which the TOC data will be returned. The data is re-

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turned in contiguous ascending order. Valid values for the starting track field are 0h to 63h. A value of AAh requests that
the starting address of the lead out area be returned. If this value is zero, the table of contents data will begin with the first
track on the disc.
If the starting track field is not valid for the currently installed medium, the command shall be terminated with CHECK
CONDITION status. The sense key shall be set to ILLEGAL REQUEST and the additional sense code set to INVALID
FIELD IN COMMAND PACKET.
NOTE The maximum TOC data length possible on currently available CD-ROM media is 804 bytes, or 100 TOC track descriptors.

Table 126 - Read TOC Data Format (With Format Field = 00b)
Bit
Byte
0
1
2
3

7

6

5

MSB

4

3

2

1

0

TOC Data Length
LSB
First Track Number
Last Track Number

TOC Track Descriptors
0
1
2
3
4
5
6
7

Reserved
ADR

MSB

Control
Track Number
Reserved
Absolute CD-ROM Address
See "Table 27 - MSF Address Format" on page 78
LSB

The TOC Data Block contains a four-byte header followed by zero or more TOC track descriptors.
The TOC Data Length specifies the length in bytes of the following TOC data that is available to be transferred to the
Host. The TOC Data Length Value does not include the TOC Data Length field itself.
The First Track Number field indicates the first track number in the table of contents. Valid track numbers are from 01d
to 99d (63h).
The Last Track Number field indicates the last track number in the table of contents before the lead-out track number.
The First Track Number is not required to be one. A disc may start at any valid track number. The track numbers between the First Track Number and the Last Track Number are required to be in contiguous ascending order, except for
the lead-out track.
The ADR field gives the type of information encoded in the Q sub-channel of the block where this TOC entry was found.
The possible ADR values are defined in "Table 117 - ADR Sub-channel Q Field" on page 163.
The Control field indicates the attributes of the track. The possible Control field values are defined in "Table 133 - Values
for Control Field in Sub-channel Q" on page 176.
The Track Number field indicates the track number for which the data in the TOC track descriptor is valid. A track number of 0AAh indicates that the track descriptor is for the start of the lead-out area.

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READ TOC Command
The Absolute CD-ROM Address contains the address of the first block with user information for that track number as
read from the table of contents. If the MSF bit in the READ TOC is zero, the absolute CD-ROM address field contains a
logical block address. If the MSF bit is one, the absolute CD-ROM address field contains an MSF address.
The Starting Logical Block Address Value recovered from the TOC has a tolerance of zero for data tracks and plus or minus 75 CD sectors for audio tracks. This tolerance is multiplied by a factor dependent on the logical block length.

Table 127 - Read TOC Data Format (With Format Field = 01b)
Bit
Byte
0
1
2
3

7

6

5

MSB

4

3

2

1

0

TOC Data Length (0Ah)
LSB
First Session Number
Last Session Number

TOC Track Descriptors
0
1
2
3
4
5
6
7

Reserved
ADR

MSB

Control

First Track Number in Last Session
Reserved
Absolute CD-ROM Address of First Track in Last Session
See "Table 27 - MSF Address Format" on page 78
LSB

For Format field 10b, the drive should return TOC data for Q-subcode mode (ADR field) 1 and 5 (Except mode 5, point 1
through 40) in the lead in area.
The First Session Number is equal to the Last Session Number for single session discs or if the drive does not support
multi-session discs.
The TOC Data Length shall be 10 (0Ah).

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Table 128 - Read TOC Data Format (With Format Field = 10b)
Bit
Byte
0
1
2
3

7
MSB

6

5

4

3

2

1

0

TOC Data Length (2 + (11 * The number of Descriptors returned))
LSB
First Session Number
Last Session Number

TOC Track Descriptors
0
1
2
3
4
5
6
7
8
9
10

Session Number
ADR

Control
TNO (0)
Point
Byte 3 or Min
Byte 4 or Sec
Byte 5 or Frame
Byte 6 or Zero
Byte 7 or PMin
Byte 8 or PSec
Byte 9 or PFrame

See Table 131, “Lead in Area (TOC), Sub-channel Q formats,” on page 175 and section 10.8.19.2 on page 177 for a detailed description of bytes 2-10 above.
The returned TOC data of a multi-session disc is arranged in ascending order of the session number. The TOC data within a session is arranged in the order of Q Subcode Point Field value of A0h, A1h, A2h; Track Numbers B0h, B1h, B2h,
B3h, B4h and C0h.
The TOC data returned shall be sorted according to the following rules:
1.

Each session of a multisession disk shall be returned independently. No mixing of any of the pointers from each
session shall occur.

2.

The first TOC entries shall be the A0, A1, A2h pointers from the session. Note that in many cases these pointers
are placed at the end of the actual TOC data on the media.

3.

Following the Ax pointers will be all the Track Pointer entries.

4.

Last will be any Bx, Cx or other reserved value pointers.

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Table 129 - TOC Track Descriptors
Byte

Action

Description

Byte 0

Return a hex value

Session Number

Byte 1

No conversion, return as is

ADR / Cntrl

Byte 2

0

Track (TOC = 0)

Byte 3

If 0-99, then convert to hex

Point

Bytes 4 - 6

Conversion based on Point

MSF Field

Point 00-99

Value should be 00h

Point A0h - AFh

Value should be 00h

Point B0h

Convert to hex

NRA

Point B1h - BFh

Convert to hex

Skip Values

Point C0

No Conversion

ORP / App Code

No Conversion

Reserved

Conversion based on Point

ZERO Field

Point C1 - FFh
Byte 7
Point 00h - AFh

Value should be 00h

Point B0h - BFh

Convert to Hex

# Pntrs / Skip

Point C0h - FFh

No Conversion

Reserved

Conversion based on Point

ZERO Field

Point 00 - 99

Convert to hex

Track Start

Point A0h

Convert PMIN to hex, PSEC is retruned
as is

1st / Last / Start LO

Point A1h - AFh

Convert to hex

1st / Last / Start LO

Point B0h

Convert to hex

Lead Out Max

Point B1h - BFh

Convert to hex

Skip Values

Point C0h

Convert to hex

ORP / App Code

Point C1h - FFh

No conversion

Reserved

Bytes 8 - 10

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Table 130 - Recommended Sense Key, ASC and ASCQ for Read TOC Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

02

57

05

00

Page 174

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00

11

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT
UNABLE TO RECOVER TABLE OF CONTENTS
PLAY OPERATION IN PROGRESS

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ATAPI CD-ROM Specification
READ TOC Command
10.8.19.1 Sub-channel Q TOC information

Table 131 - Lead in Area (TOC), Sub-channel Q formats
S0,S1

Control /
ADR

TNO

Point

4/6
4/6

1
1

00
00

01-99
A0

4/6

1

00

A1

4/6
4/6

1
5

00
00

A2
B0

4/6

5

00

B1

4/6
4/6

5
5

00
00

B2-B4
01-40

4/6

5

00

C0

Point

Min

Sec

Frame

00 (Absolute time is allowed)
00 (Absolute time is allowed)

Zero

Pmin

PSec

CRC
x16+x12
+x5+1

PFrame

00
00

Start position of track
First Track Disc Type 00
num
00 (Absolute time is allowed)
00
Last Track 00
00
num
00 (Absolute time is allowed)
00
Start position of the Lead-out area
Start time of next possible pro- # of point- Maximum start time of the outermost
gram in the Recordable Area of ers in Mode Lead Out area in the Recordable Area
the Hybrid Disc
5
of the Hybrid Disc
00
# of Skip
00
00
00
00
# of Skip
Track
Interval
Pointers
Pointers
(N<=21)
(N<=40)
Skip #
Skip #
Skip #
Skip #
Skip #
Skip #
Skip #
Ending time for the interval that Reserved
Start time for interval that should be
should be skipped
skipped on playback
Applica- Reserved Reserved
Start time of the first Lead In Area of
Optition Code
the Hybrid Disc
mum
recording
power

The Point field defines various types of information:
01-99
A0
A1
A2
B0

Track number references
First Track number in the program area
Last Track number in the program area
Start location of the Lead-out area
Used to identify a Hybrid Disc (Photo CD)
Contains start time of next possible program area
B1
Number of Skip Interval Pointers & Skip Track assignments
01-40 Skip Interval Pointers
B2-B4 Skip Track Assignment Pointers
C0
Start time of first Lead In area of Hybrid Disc
This only exists in the first Lead In area
Disc Type Byte

This byte contains a definition of the type of disc
00h
10h
20h

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CD-DA or CD-ROM with first track in Mode 1
CD-I disc
CD-ROM XA disc with first track in Mode 2

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READ TOC Command

Table 132 - Bit Definitions for the Control Field in Sub-channel Q
Control Field
00x0
00x1
0x0x
0x1x
01x0
1xxx

Definition
2 Audio without Pre-emphasis
2 Audio with Pre-emphasis
Copy Prohibited
Copy Permitted
Digital Data
Broadcast Data (TBD)

Table 133 - Values for Control Field in Sub-channel Q
Control Field value

Description

00h
01h
02h
03h
04h
05h
06h
07h
08h - 0Fh

Copy Prohibited, 2 Audio with out pre-emphasis
Copy Prohibited, 2 Audio with pre-emphasis
Copy Permitted, 2 Audio with out pre-emphasis
Copy Permitted, 2 Audio with pre-emphasis
Copy Prohibited, Digital Data
Copy Prohibited, RESERVED
Copy Permitted, Digital Data
Copy Permitted, RESERVED
Broadcast use

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READ TOC Command
10.8.19.2 Example Read TOC Operations
The following example is based on a 4-session, 12-track PhotoCD disc. Data structure is shown as the data to Host.
Command Packet: 43h 00 00 00 00 00 00 10h 00 80h 00 00

Table 134 - Example Read TOC Operations

Ses:
A/C:
TNO:
Pnt:

Ses

A/C

TNO

Pnt

Min Sec Frame

Zero

PMin PSec PFrame

01
01
01
01
01
01
01
01
02
02
02
02
02
02
02
03
03
03
03
03
03
03
04
04
04
04
04
04
04

14
14
14
14
14
14
54
54
14
14
14
14
14
14
54
14
14
14
14
14
14
54
14
14
14
14
14
14
54

00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00

A0
A1
A2
01
02
03
B0
C0
A0
A1
A2
04
05
06
B0
A0
A1
A2
07
08
09
B0
A0
A1
A2
0A
0B
0C
B0

00 00 00
00 00 00
00 00 00
00 00 00
00 00 00
00 00 00
04 26 3F
C0 00 00
00 00 00
00 00 00
00 00 0
00 00 00
00 00 00
00 00 00
09 2C 08
00 00 00
00 00 00
00 00 00
00 00 00
00 00 00
00 00 00
20 09 32
00 00 00
00 00 00
00 00 00
00 00 00
00 00 0
00 00 00
13 39 1A

00
00
00
00
00
00
02
00
00
00
00
00
00
00
01
00
00
00
00
00
00
01
00
00
00
00
00
00
01

01 20 00
03 00 00
02 08 3F
00 02 00
00 08 02
00 15 32
40 02 00
61 2C 00
04 20 00
06 00 00
08 20 08
04 28 3F
04 2E 41
06 27 36
40 02 00
07 20 00
09 00 00
0C 27 32
09 2E 08
09 34 10
0B 04 24
40 02 00
0A 20 00
0C 00 00
12 1B 1A
0E 0B 32
0E 11 34
11 08 22
40 02 00

Comments
First track is 1. XA disc
Last track is 3
Lead Out Area on 1st session
Start address of track 1
Start address of track 2
Start address of track 3
Next recordable area address
Hybrid disc
1st track on 2nd session is 4
Last track on 2nd session is 6
Lead Out Area on 2nd session
Start address of track 4
Start address of track 5
Start address of track 6
Next recordable area address
1st track on 3rd session is 7
Last track on 3rd session is 9
Lead Out Area on 3rd session
Start address of track 7
Start address of track 8
Start address of track 9
Next recordable area address
1st track on 4th session is 10
Last track on 4th session is12
Lead Out Area on 4th session
Start address of track 10
Start address of track 11
Start address of track 12
Next recordable area address

session number
ADR/Control
00 for Lead In area
POINT

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ATAPI Packet Commands for CD-ROM devices
READ TOC Command

If you use the following command on this disc, Command Packet: 43h 00 00 00 00 00 00h 10h 00 40h 00 00, return data
would be:

Table 135 - Values for Control Field in Read TOC
Control Field value
01h
04h
00h
14h
0Ah (10d)
00h
00h,00h,F8h,EDh (In
LBA format, 63725 )

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Description
First Session Number
Last Session Number
Reserved
ADR/Control
First Track Number in Last session
Reserved
Absolute CD-ROM address of first track in last
session
-> 14M 9S 50F
-> add 2 sec: 14M 11S 50F

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ATAPI CD-ROM Specification
REQUEST SENSE Command
10.8.20 REQUEST SENSE Command
The REQUEST SENSE command requests that the ATAPI CD-ROM Drive transfer sense data to the Host Computer.

Table 136 - Request Sense Command
Bit
Byte

7

0
1
2
3
4
5
6
7
8
9
10
11

6

5

4

3

2

1

0

Operation code (03h)
Reserved
Reserved
Reserved
Allocation Length
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved

The sense data:
1.

shall be available if an error condition (CHECK CONDITION) had previously been reported to the Host Computer;

2.

shall be available if other information (e.g. medium position) is available in any field.

If the ATAPI CD-ROM Drive has no other sense data available to return, it shall return a sense key of NO SENSE and an
additional sense code of NO ADDITIONAL SENSE INFORMATION.
The sense data shall be preserved by the ATAPI CD-ROM Drive until retrieved by a REQUEST SENSE command or until the receipt of any other I/O Command.
The ATAPI CD-ROM Drive shall return CHECK CONDITION status for a REQUEST SENSE command only to report
exception conditions specific to the command itself. For example:
1.

An ATAPI CD-ROM Drive malfunction prevents return of the sense data.

If a recovered error occurs during the execution of the REQUEST SENSE command, the ATAPI CD-ROM Drive shall
return the sense data with GOOD status. If an ATAPI CD-ROM Drive returns CHECK CONDITION status for a REQUEST SENSE command, the sense data may be invalid.
ATAPI CD-ROM Drives shall be capable of returning at least 18 bytes of data in response to a REQUEST SENSE command. If the allocation length is 18 or greater, and an ATAPI CD-ROM Drive returns less than 18 bytes of data, the Host
Computer should assume that the bytes not transferred would have been zeros had the ATAPI CD-ROM Drive returned
those bytes. Host Computers can determine how much sense data has been returned by examining the allocation length
parameter in the Command Packet and the additional sense length in the sense data. ATAPI CD-ROM Drives shall not
adjust the additional sense length to reflect truncation if the allocation length is less than the sense data available.
The sense data format for error codes 70h (current errors) and 71h (deferred errors) are defined in "Table 137 - Request
Sense Standard Data" on page 180. Error code values of 72h to 7Eh are reserved. Error code 7Fh is for a vendor-specific

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ATAPI Packet Commands for CD-ROM devices
REQUEST SENSE Command

sense data format. ATAPI CD-ROM Drives shall implement error code 70h; implementation of error code 71h is optional. Error code values of 00h to 6Fh are not defined by this Specification and their use is not recommended.

Table 137 - Request Sense Standard Data
Bit
Byte
0
1
2
3
6
7
8
11
12
13
14
15

7

6

5

4

Valid
Reserved

ILI

3

2

Error Code (70h or 71h)
Segment Number (Reserved)
Reserved
Information

1

0

Sense Key

Additional Sense Length (n - 7)
Command Specific Information

SKSV
(Optional)

17
18
n

Additional Sense Code
Additional Sense Code Qualifier (Optional)
Field Replaceable Unit Code (Optional)
Sense Key Specific (Optional)

Additional Sense Bytes

A Valid bit of zero indicates that the information field is not as defined in this Specification. A Valid bit of one indicates
the information field contains valid information as defined in this Specification. ATAPI CD-ROM Drives shall implement the Valid bit.
The Segment Number field is Reserved.
An Incorrect Length Indicator (ILI) bit of one indicates that the requested allocation length did not match the logical
block length of the data on the medium.
The Sense Key, Additional Sense Code and Additional Sense Code Qualifier provide a hierarchy of information. The intention of the hierarchy is to provide a top-down approach for a Host Computer to determine information relating to the
error and exception conditions. The Sense Key provides generic categories in which error and exception conditions can
be reported. Host Computers would typically use sense keys for high-level error recovery procedures. Additional Sense
Codes provide further detail describing the sense key. Additional Sense Code Qualifiers add further detail to the additional sense code. The Additional Sense Code and Additional Sense Code Qualifier can be used by Host Computers where
sophisticated error recovery procedures require detailed information describing the error and exception conditions.
The Sense Key field is mandatory and indicates generic information describing an error or exception condition. The sense
keys are defined in section Table 140 -, "Sense Key Descriptions", on page 183.
The contents of the Information field is command-specific and is defined within the appropriate section for the command
of interest. ATAPI CD-ROM Drives shall implement the Information field. Unless specified otherwise, this field contains
the unsigned logical block address associated with the sense key.
The Additional Sense Length field indicates the number of additional sense bytes to follow. If the allocation length of the
Command Packet is too small to transfer all of the additional sense bytes, the Additional Sense Length is not adjusted to
reflect the truncation.

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ATAPI CD-ROM Specification
REQUEST SENSE Command
The Command-specific Information field contains information that depends on the command that was executed. Further
meaning for this field is defined within the command description.
The Additional Sense Code (ASC) field indicates further information related to the error or exception condition reported
in the Sense Key field. ATAPI CD-ROM Drives shall support the Additional Sense Code field. Support of the additional
sense codes not explicitly required by this Specification is optional. A list of additional sense codes is in "Table 141 ASC and ASCQ Assignments" on page 184. If the ATAPI CD-ROM Drive does not have further information related to
the error or exception condition, the Additional Sense Code is set to NO ADDITIONAL SENSE INFORMATION.
The Additional Sense Code Qualifier (ASCQ) indicates detailed information related to the Additional Sense Code. The
ASCQ is optional. If the error or exception condition is reportable by the device, the value returned shall be as specified
in "Table 141 - ASC and ASCQ Assignments" on page 184. If the ATAPI CD-ROM Drive does not have detailed information related to the error or exception condition, the ASCQ is set to zero.
Non-zero values in the Field Replaceable Unit Code field are used to define a device-specific mechanism or unit that has
failed. A value of zero in this field shall indicate that no specific mechanism or unit has been identified to have failed or
that the data is not available. The Field Replaceable Unit Code field is optional. The format of this information is not
specified by this Specification. Additional information about the field replaceable unit may be available in the ASCII information page, if supported by the ATAPI CD-ROM Drive.
The Additional Sense Bytes field may contain command specific data, peripheral device specific data, or vendor-specific
data that further defines the nature of the CHECK CONDITION status.

10.8.20.1 Sense-key Specific
The Sense-key Specific field is defined by this Specification when the value of the Sense-key Specific Valid (SKSV) bit is
one. The Sense-key Specific Valid bit and Sense-key Specific field are optional. The definition of this field is determined
by the value of the sense key field. This field is reserved for sense keys not described below. An SKSV value of zero indicates that this field is not as defined by this Specification.
If the Sense Key field is set to ILLEGAL REQUEST and the SKSV bit is set to one, the Sense-key Specific field indicates which illegal parameters in the Command Packet or the data parameters are in error.

Table 138 - Field Pointer Bytes
Bit
Byte
15
16
17

7

6

5

SKSV
MSB

C/D

Reserved

4

3

Reserved
BPV
Field Pointer

2

1

0

Bit Pointer
LSB

A Command Data (C/D) bit of one indicates that the illegal parameter is in the Command Packet. A C/D bit of zero indicates that the illegal parameter is in the data parameters sent by the Host Computer.
A Bit Pointer Valid (BPV) bit of zero indicates that the value in the Bit Pointer field is not valid. A BPV bit of one indicates that the Bit Pointer field specifies which bit of the byte designated by the field pointer field is in error. When a multiple-bit field is in error, the Bit Pointer field shall point to the most-significant (left-most) bit of the field.
The Field Pointer field indicates which byte of the Command Packet or of the parameter data was in error. Bytes are
numbered starting from zero, as shown in the tables describing the commands and parameters. When a multiple-byte
field is in error, the pointer shall point to the most significant (left-most) byte of the field.

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REQUEST SENSE Command

If the sense key is RECOVERED ERROR, HARDWARE ERROR or MEDIUM ERROR and if the SKSV bit is one, the
sense-key specific field shall be as shown in "Table 139 - Field Pointer Bytes" on page 182.

Table 139 - Field Pointer Bytes
Bit
Byte
15
16
17

7

6

5

SKSV
MSB

C/D

Reserved

4

3

Reserved
BPV
Actual Retry Count

2

1

0

Bit Pointer
LSB

The Actual Retry Count field returns implementation-specific information on the actual number of retries of the recovery
algorithm used in attempting to recover an error or exception condition. This field should relate to the retry count fields
within the Error Recovery Page of the MODE SELECT command.

10.8.20.2 Deferred Errors
Error code 70h indicates that the CHECK CONDITION status returned is the result of an error or exception condition on
the I/O process that returned the CHECK CONDITION status. This includes errors generated during execution of the
command by the actual execution process. It also includes errors not related to any command that are first observed during execution of a command. Examples of this latter type of error include disk servo-mechanism, off-track errors, and
power-up test errors.
Error code 71h (deferred error) indicates that the CHECK CONDITION status returned is the result of an error or exception condition that occurred during execution of a previous command for which GOOD status has already been returned.
Such commands are associated with use of the immediate bit, with some forms of caching, and with multiple command
buffering. ATAPI CD-ROM Drives that implement these features are required to implement deferred error reporting.
The deferred error may be indicated by returning CHECK CONDITION status to the Host Computer as described below. The subsequent execution of a REQUEST SENSE command shall return the deferred error sense information.
If an I/O Command terminates with CHECK CONDITION status and the subsequent sense data returns a deferred error,
that I/O command shall not have been executed. After the ATAPI CD-ROM Drive detects a deferred error condition on a
Device, it shall return a deferred error according to the rules described below:
1.

If a deferred error can be recovered with no external system intervention, a deferred error indication shall not be
posted unless required by the error handling parameters of the MODE SELECT command. The occurrence of the
error may be logged if statistical or error logging is supported.

2.

If a deferred error can be associated with a particular function or a particular subset of data, and the error is either
unrecovered or required to be reported by the mode parameters, a deferred error indication shall be returned to the
Host Computer.

Deferred errors may indicate that an operation was unsuccessful long after the command performing the data transfer returned GOOD status. If data that cannot be replicated or recovered from other sources is being stored using buffered
write operations, synchronization commands should be performed before the critical data is destroyed in the host Host
Computer. This is necessary to be sure that recovery actions can be taken if deferred errors do occur in the storing of the
data.

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ATAPI CD-ROM Specification
REQUEST SENSE Command
10.8.20.3 Sense-key and Sense Code Definitions

Table 140 - Sense Key Descriptions
Sense key

Description

0h

NO SENSE. Indicates that there is no specific sense key information to be reported. This would be the case for a
successful command.
RECOVERED ERROR. Indicates that the last command completed successfully with some recovery action performed by the ATAPI CD-ROM Drive. Details may be determinable by examining the additional sense bytes and
the information field. When multiple recovered errors occur during one command, the choice of which error to
report (first, last, most severe, etc.) is device specific.
NOT READY. Indicates that the Device cannot be accessed. Operator intervention may be required to correct this
condition.
MEDIUM ERROR. Indicates that the command terminated with a non-recovered error condition that was probably
caused by a flaw in the medium or an error in the recorded data. This sense key may also be returned if the ATAPI
CD-ROM Drive is unable to distinguish between a flaw in the medium and a specific hardware failure (sense key
4h).
HARDWARE ERROR. Indicates that the ATAPI CD-ROM Drive detected a non-recoverable hardware failure (for
example, controller failure, device failure, parity error, etc.) while performing the command or during a self test.
ILLEGAL REQUEST. Indicates that there was an illegal parameter in the Command Packet or in the additional
parameters supplied as data for some commands. If the ATAPI CD-ROM Drive detects an invalid parameter in the
Command Packet, then it shall terminate the command without altering the medium. If the ATAPI CD-ROM
Drive detects an invalid parameter in the additional parameters supplied as data, then the ATAPI CD-ROM Drive
may have already altered the medium.
UNIT ATTENTION. Indicates that the removable medium may have been changed or the ATAPI CD-ROM Drive
has been reset.
DATA PROTECT. Indicates that a command that reads the medium was attempted on a block that is protected from
this operation. The read operation is not performed.
Reserved
Reserved
ABORTED COMMAND. Indicates that the device has aborted the command. The Host may be able to recover by
trying the command again. This error is reported for conditions such as an overrun etc.
MISCOMPARE. Indicates that the source data did not match the data read from the medium.
Reserved

1h

2h
3h

4h
5h

6h
7h
8h
9h - Ah
Bh
Eh
Fh

10.8.20.4 Using the REQUEST SENSE Command
Whenever an Error is reported, the Host Computer should issue a REQUEST SENSE command to receive the sense data
describing what caused the Error condition. If the Host Computer issues some other command, the sense data is lost.

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ATAPI Packet Commands for CD-ROM devices
REQUEST SENSE Command

D - DIRECT ACCESS DEVICE
R - READ ONLY (CD-ROM) DEVICE
O - OPTICAL MEMORY DEVICE
M - MEDIA CHANGER DEVICE
ASC

ASCQ

DROM

00
00
00
00
00
00
01
02
04
04
04
04
05
06
09
09
09
09
11
11
15
15
15
17
17
17
17
17
17
18
18
18
18
18
1A
20
21
24
26
26
26

00
11
12
13
14
15
00
00
00
01
02
03
01
00
00
01
02
03
00
06
00
01
02
00
01
02
03
04
05
00
01
02
03
04
00
00
00
00
00
01
02

DROM
R
R
R
R
R
R
DROM
DROM
DROM
DROM
DROM
DROM
DROM
DRO
RO
RO
RO
DRO
RO
DROM
DROM
DRO
DRO
DRO
DRO
DRO
RO
DRO
DRO
DRO
DRO
R
R
DROM
DROM
DROM
DROM
DROM
DROM
DROM

DESCRIPTION
NO ADDITIONAL SENSE INFORMATION
PLAY OPERATION IN PROGRESS
PLAY OPERATION PAUSED
PLAY OPERATION SUCCESSFULLY COMPLETED
PLAY OPERATION STOPPED DUE TO ERROR
NO CURRENT AUDIO STATUS TO RETURN
MECHANICAL POSITIONING OR CHANGER ERROR
NO SEEK COMPLETE
LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED
MEDIA LOAD - EJECT FAILED
NO REFERENCE POSITION FOUND
TRACK FOLLOWING ERROR
TRACKING SERVO FAILURE
FOCUS SERVO FAILURE
SPINDLE SERVO FAILURE
UNRECOVERED READ ERROR
CIRC UNRECOVERED ERROR
RANDOM POSITIONING ERROR
MECHANICAL POSITIONING OR CHANGER ERROR
POSITIONING ERROR DETECTED BY READ OF MEDIUM
RECOVERED DATA WITH NO ERROR CORRECTION APPLIED
RECOVERED DATA WITH RETRIES
RECOVERED DATA WITH POSITIVE HEAD OFFSET
RECOVERED DATA WITH NEGATIVE HEAD OFFSET
RECOVERED DATA WITH RETRIES AND/OR CIRC APPLIED
RECOVERED DATA USING PREVIOUS SECTOR ID
RECOVERED DATA WITH ERROR CORRECTION APPLIED
RECOVERED DATA WITH ERROR CORRECTION & RETRIES APPLIED
RECOVERED DATA - THE DATA WAS AUTO-REALLOCATED
RECOVERED DATA WITH CIRC
RECOVERED DATA WITH L-EC
PARAMETER LIST LENGTH ERROR
INVALID COMMAND OPERATION CODE
LOGICAL BLOCK ADDRESS OUT OF RANGE
INVALID FIELD IN COMMAND PACKET
INVALID FIELD IN PARAMETER LIST
PARAMETER NOT SUPPORTED
PARAMETER VALUE INVALID

Table 141 - ASC and ASCQ Assignments
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ATAPI CD-ROM Specification
REQUEST SENSE Command
ASC

DROM

ASCQ

DESCRIPTION

28
00
DROM
29
00
DROM
2A
00
DROM
2A
01
DROM
30
00
DROM
30
01
DRO
30
02
DRO
39
00
DROM
3A
00
DROM
3F
00
DROM
3F
01
DROM
40
NN
DROM
44
00
DROM
4E
00
DROM
53
00
DROM
53
02
DROM
57
00
R
5A
00
DROM
5A
01
DROM
63
00
R
64
00
R
B9
00
R
BF
00
R
80h XXh THROUGH FFh XX
XXh 80h THROUGH XXh DDh

NOT READY TO READY TRANSITION, MEDIUM MAY HAVE CHANGED
POWER ON, RESET OR BUS DEVICE RESET OCCURRED
PARAMETERS CHANGED
MODE PARAMETERS CHANGED
INCOMPATIBLE MEDIUM INSTALLED
CANNOT READ MEDIUM - UNKNOWN FORMAT
CANNOT READ MEDIUM - INCOMPATIBLE FORMAT
SAVING PARAMETERS NOT SUPPORTED
MEDIUM NOT PRESENT
ATAPI CD-ROM DRIVE OPERATING CONDITIONS HAVE CHANGED
MICROCODE HAS BEEN CHANGED
DIAGNOSTIC FAILURE ON COMPONENT NN (80H-FFH)
INTERNAL ATAPI CD-ROM DRIVE FAILURE
OVERLAPPED COMMANDS ATTEMPTED
MEDIA LOAD OR EJECT FAILED
MEDIUM REMOVAL PREVENTED
UNABLE TO RECOVER TABLE OF CONTENTS
OPERATOR REQUEST OR STATE CHANGE INPUT (UNSPECIFIED)
OPERATOR MEDIUM REMOVAL REQUEST
END OF USER AREA ENCOUNTERED ON THIS TRACK
ILLEGAL MODE FOR THIS TRACK
PLAY OPERATION OBORTED
LOSS OF STREAMING
Vendor-specific.
Vendor-specific QUALIFICATION OF STANDARD ASC.
ALL CODES NOT SHOWN ARE RESERVED.

Table 141 - ASC and ASCQ Assignments

Table 142 - Recommended Sense Key, ASC and ASCQ for Request Sense Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

working draft ATAPI

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

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REQUEST SENSE Command

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ATAPI CD-ROM Specification
SCAN Command
10.8.21 SCAN Command
The SCAN command requests a fast-forward or fast-reverse scan operation starting from the Scan Starting Address. The
command shall scan all the way to the end of the media (last audio track).
This command responds with immediate status, allowing overlapped commands. This command shall set the DSC bit
upon command completion. See also "10.4 Immediate Command Processing Considerations" on page 90.
A Direction (DIRECT) bit of zero indicates a fast-forward. A DIRECT bit of one indicates a fast-reversed operation.
The Scan Starting Address specifies the address at which the Audio Fast Scan shall begin. The Type Field determines the
interpretation of the address.
Like the Audio Play Command, the SCAN Command shall terminate the scan at the last audio track or upon receipt of
the STOP PLAY / SCAN Command. Upon receipt of the STOP PLAY / SCAN Command the Device shall set the current address to the last address output during the SCAN Command. Subsequent Audio Play Commands shall cause the
device to begin playing at the location last output by the SCAN Command. If the drive receives a PAUSE/RESUME
Command with the resume bit clear, the drive shall pause. After that, if the drive receives a PAUSE/RESUME Command
with the resume bit set, the drive shall resume audio play (note: not scan) from the address where the audio pause occurred. See "Figure 15 - Stop Play/Play Audio/Audio Scan/Pause/Resume Sequencing" on page 196 for additional information.
If the drive receives a SCAN Command during play or pause, the drive shall stop play or pause and perform Scan.
Upon receipt of a READ SUB-CHANNEL Command during scan, the drive shall return an Audio Status of 11h (Audio
Play operation in Progress).
If the drive receives a SCAN Command during play or pause for which a valid stop address was specified, the drive will
remember the stop address but ignore it during the scan command. The stop address becomes valid again when audio
play resumes. Thus, upon resumption of audio play, if the current address is greater than the former stop address, the
drive shall stop playing and return good status. After this, if the drive receives a READ SUB-CHANNEL Command, the
drive shall return an Audio Status of 13h (Audio Play operation successfully completed).
If the drive reaches a data track, it shall stop scan.
Request to the implementer: The following implementation of forward and reverse scan speed will provide good quality
soud: Forward scan - [Play six CD-DA blocks and then jump 190* CD-DA blocks in the forward direction. Reverse
scan - play six CD-DA blocks and then jump 150* CD-DA blocks (from the last block of the six) in the reverse direction.
*This can be some fixed number between 150 and 200..

Table 143 - SCAN Command
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

7

6

Reserved

5

4

3

2

Operation code (BAh)
DIRECT

1

0

Reserved

MSB

working draft ATAPI

Scan Starting Address Field
LSB
Reserved

Type

Reserved
Reserved
Reserved

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Bits 7-6

ATAPI Packet Commands for CD-ROM devices
SCAN Command

Type

This field specifies the “Type” of address contained in the Scan Starting Address Field.
0
0
1
1

0
1
0
1

Logical Block Address format
AMIN, ASEC and AFRAME format
Track Number (TNO) format
Reserved

See "10.8.8.1 Play Audio with Immediate Packet Commands" on page 126 for information on overlapped commands
during a SCAN operation.

Table 144 - Scan Starting Address in Logical Block Format
Bit
Byte
2
3
4
5

7

6

5

4

3

2

1

0

MSB
Scan Starting Address Field
LSB

Table 145 - Scan Starting Address in AMIN, ASEC and AFRAME Format
Bit
Byte

7

6

5

2
3
4
5

4

3

2

1

0

Reserved
CD-absolute time (AMIN)
CD-absolute time (ASEC)
CD-absolute time (AFRAME)

The AMIN, ASEC and AFRAME fields specifies the relative running time from the beginning of the disc. The AMIN
field has a range of 00 to 99d (63h). The ASEC ranges from 00 to 59d (3Bh). The AFRAME field has a range of 00 to
74d (4Ah). All MSF fields shall be Binary.

Table 146 - Scan Starting Address in Track Number (TNO) Format
Bit
Byte
2
3
4
5

7

6

5

4

3

2

1

0

Reserved
Reserved
Reserved
Track Number (TNO)

The Track Number field specifies the track in binary notation at which the scan operation will begin. This field has a
range of 01h to 63h.

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ATAPI CD-ROM Specification
SCAN Command

Table 147 - Recommended Sense Key, ASC and ASCQ for Scan Command Errors
Sense Key

ASC

ASCQ

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
3A

03

02

02

06

00

02

30

00

02

30

01

02

30

02

05

21

05

64

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

MEDIUM NOT PRESENT
NO SEEK COMPLETE
NO REFERENCE POSITION FOUND (media may be upside down)
INCOMPATIBLE MEDIUM INSTALLED
CANNOT READ MEDIUM - UNKNOWN FORMAT
CANNOT READ MEDIUM - INCOMPATIBLE FORMAT
LOGICAL BLOCK ADDRESS OUT OF RANGE
ILLEGAL MODE FOR THIS TRACK OR INCOMPATIBLE MEDIUM

When a Play CD command is actively using one of the Digital Output ports a Scan command shall be aborted with error
(05/64) ILLEGAL MODE FOR THIS TRACK.

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SCAN Command

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ATAPI CD-ROM Specification
SEEK Command
10.8.22 SEEK Command
The SEEK command request that the Device seek to the specified logical block address. All Logical Block Addresses are
valid targets for a seek operation, including a CD-DA audio sector. The content of the Sector at the specified LBA shall
not affect the seek operation nor cause an error to be generated.
The SEEK Command will always be executed as an immediate command. The command will return completion stations
as soon as the seek operation has been started.

Table 148 - SEEK Command
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

7

6

5

4

3

2

1

0

Operation code (2Bh)
Reserved
Logical Block Address

MSB

LSB
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved

Table 149 - Recommended Sense Key, ASC and ASCQ for Seek Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

03

02

05

21

working draft ATAPI

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT
NO SEEK COMPLETE
LOGICAL BLOCK ADDRESS OUT OF RANGE

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ATAPI Packet Commands for CD-ROM devices
SEEK Command

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ATAPI CD-ROM Specification
SET CD SPEED Command
10.8.23 SET CD SPEED Command
The SET CD SPEED command provides a means for the Host to set the spindle speed to be used while reading and writing CD data. Note that the Play commands may not use the speed set by this command.

Table 150 - SET CD-ROM SPEED Command
Bit
Byte
0
1
2
3
4
5
6
7
8
9
10
11

7

6

5

4

3

2

MSB

Operation code (BBh)
Reserved
Read Drive Speed in Kbytes/Second

MSB

Reserved for Write Drive Speed in Kbytes/Second

1

0

LSB
LSB
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved

The Drive Speed parameter contains the requested Data Rate the drive should use. The drive may choose to select the
speed specified or any slower rate. A value of FFFFh will set the Drive Speed to the Maximum supported. Requesting a
speed faster than the drive supports will not generate an error. The actual maximum speed supported is returned in the
Capabilities Mode Sense page (See "10.8.6.4 CD-ROM Capabilities and Mechanical Status Page" on page 118.)
If the speed selected is less than 1x, then the drive shall reject the command, and not change the speed.

Table 151 - Recommended Sense Key, ASC and ASCQ for SET CD SPEED Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

working draft ATAPI

ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT

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ATAPI Packet Commands for CD-ROM devices
SET CD SPEED Command

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ATAPI CD-ROM Specification
STOP PLAY / SCAN CD-ROM Command
10.8.24 STOP PLAY / SCAN CD-ROM Command
The STOP PLAY/ SCAN CD-ROM Command stops playback of CD-ROM audio commands.

Table 152 - STOP PLAY / SCAN CD-ROM Command
Bit
Byte

7

6

0
1
2
3
4
5
6
7
8
9
10
11

5

4

3

2

1

0

Operation code (4Eh)
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved

Table 153 - Recommended Sense Key, ASC and ASCQ for STOP PLAY CD-ROM Command
Errors
Sense Key

ASC

ASCQ

Description of Error

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
05

00
01
02
03

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

02

06

00

02

3A

MEDIA LOAD OR EJECT FAILED
NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT

INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

Issuing a Stop Play / Scan command while the drive is scanning shall result in continuation of the play command. Issuing
a Stop Play / Scan command while the drive is paused shall stop the play command

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ATAPI Packet Commands for CD-ROM devices
STOP PLAY / SCAN CD-ROM Command

INITIALIZED
Play

Scan

Stop
or end
of track

Stop

Stop
or end of track
Play

Scan

SCAN

PLAY

Resume or Play

Pause

Pause

Play or Resume

Scan

PAUSED

Figure 15 - Stop Play/Play Audio/Audio Scan/Pause/Resume Sequencing

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ATAPI CD-ROM Specification
START/STOP UNIT Command
10.8.25 START/STOP UNIT Command
The START/STOP UNIT command requests that the ATAPI CD-ROM Drive enable or disable media access operations.

Table 154 - START/STOP UNIT Command
Bit
Byte

7

6

0
1
2
3
4
5
6
7
8
9
10
11

5

4

3

Operation code (1Bh)
Reserved
Reserved
Reserved
Reserved

2

1

0

Immed

LoEj

Start

Reserved
Reserved
Reserved
Reserved
Reserved
Reserved

An immediate (Immed) bit of one indicates that status shall be returned as soon as the Command Packet has been validated. An Immed bit of zero indicates that status shall be returned after the operation is completed.
A start bit of one requests the Device be made ready for use. A start bit of zero requests that the Device be stopped (media cannot be accessed by the Host Computer).

Table 155 - Start/Stop and Eject Operations
LoEj

Start

Operation to be Performed

0
0
1

0
1
0

1

1

Stop the Disc
Start the Disc and read the TOC
Eject the Disc if possible (See "Table 84 - Actions for Lock / Unlock / Eject" on page
136)
Load the Disc (Close Tray)

Any attempt to Eject or Load a Disc when the Drive does not support that capability shall result in an error condition being reported to the Host (Sense key 05 ILLEGAL REQUEST, Sense Code 24 INVALID FIELD IN COMMAND PACKET.)
A load eject (LoEj) bit of zero requests that no action be taken regarding loading or ejecting the medium. A LoEj bit of
one requests that the medium be unloaded if the start bit is zero. A LoEj bit of one requests that the medium be loaded if
the start bit is one.
When the Loading Mechanism Type is a Changer utilizing individual disc change capability (4h), the Eject operation
shall only eject the disc that is currently in the Play Position. If the Loading Mechanism is a changer utilizing a Cartridge (5h), then the Cartridge shall only be ejected when no media is in the play position.

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ATAPI Packet Commands for CD-ROM devices
START/STOP UNIT Command

Table 156 - Actions for Eject/Load Disc
Locked /
Unlocked

Operation
Eject

Manual Eject

If Drive Not Ready
(No Media)

If Drive Ready
(Media Present)

Unlocked

No Error and Tray is opened

Locked

Error:
02 Not ready, 53 Media Removal Prevented
Error:
02 Not ready, 53 Media Removal Prevented

No Error:
Media Ejects
Error:
02 Not ready, 53 Media Removal Prevented
Error:
02 Not ready, 53 Media Removal Prevented

Error:
02 Not ready, 53 Media Removal Prevented

Error:
02 Not ready, 53 Media Removal Prevented

Tray opens (If tray exists)
No operation occurs

Media is Ejected
No operation, Media stays locked in drive

Changer using
Cartridge with
Disc in Play Position
Changer using
Individual disc
changability with
no Disc in the Play
Position
Unlocked
Locked

Table 157 - Recommended Sense Key, ASC and ASCQ for SEEK Command Errors
Sense Key

ASC

05

20

05

24

06

28

06

29

02
02
02
02
02

04
04
04
04
06

02

3A

02
04

53
B6

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ASCQ

Description of Error
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET
NOT READY TO READY TRANSITION
POWER ON, RESET OR BUS DEVICE RESET OCCURRED

00
01
02
03
00
02

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

NO REFERENCE POSITION FOUND (media may be upside down)
MEDIUM NOT PRESENT
MEDIA REMOVAL PREVENTED
MEDIA LOAD MECHNISM FAILED

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ATAPI CD-ROM Specification
TEST UNIT READY Command
10.8.26 TEST UNIT READY Command
The TEST UNIT READY command provides a means to check if the Device is ready. This is not a request for a selftest. If the Device would accept an appropriate medium-access command without returning CHECK CONDITION status, this command shall return a GOOD status. If the Device cannot become operational or is in a state such that an Host
Computer action (e.g. START/STOP UNIT command with LoEj = 0 & Start = 1) is required to make the unit ready, the
ATAPI CD-ROM Drive shall return CHECK CONDITION status with a sense key of NOT READY.

Table 158 - Test Unit Ready Command
Bit
Byte

7

0
1
2
3
4
5
6
7
8
9
10
11

6

5

4

3

2

1

0

Operation code (00h)
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved

10.8.26.1 Using the TEST UNIT READY Command
The TEST UNIT READY command is useful in that it allows a Host Computer to poll a Device until it is ready without
the need to allocate space for returned data. It is especially useful to check cartridge status. ATAPI CD-ROM Drives are
expected to respond promptly to indicate the current status of the device.

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ATAPI Packet Commands for CD-ROM devices
TEST UNIT READY Command

Table 159 - Recommended Sense Key, ASC and ASCQ for MODE SELECT Command Errors
Sense Key

ASC

ASCQ

Description of Error

00

00

00

05

20

05

24

NO ADDITIONAL SENSE INFORMATION
INVALID COMMAND OPERATION CODE
INVALID FIELD IN COMMAND PACKET

02
02
02
02
02

04
04
04
04
06

00
01
02
03
00

LOGICAL DRIVE NOT READY - CAUSE NOT REPORTABLE
LOGICAL DRIVE NOT READY - IN PROGRESS OF BECOMING READY
LOGICAL DRIVE NOT READY - INITIALIZING COMMAND REQUIRED
LOGICAL DRIVE NOT READY - MANUAL INTERVENTION REQUIRED

02

30

00

02

30

01

02

30

02

02

3A

NO REFERENCE POSITION FOUND (media may be upside down)
INCOMPATIBLE MEDIUM INSTALLED
CANNOT READ MEDIUM - UNKNOWN FORMAT
CANNOT READ MEDIUM - INCOMPATIBLE FORMAT
MEDIUM NOT PRESENT

Note: Some drives return ASC/ASCQ with audio, status and sense code 00 when there is no error condition.

(02/04/00)
POR

Stop / Unload

Not Ready

Media In

Spin Up / Load

Media
Not
Present
(02/3A/--)

Ready
(00/--/--)

Can’t
Read

Eject / Unload

No Media

Toc Ok

Read
TOC

No Media

Spin Up
Bad
Media

(02/06/00)
(02/30/--)
Figure 16 - Test Unit Ready State Diagram

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ATAPI CD-ROM Specification
Physical Interface

11.0 Physical Interface
Digital Analog
Audio Audio
1

4

DIG
GND

2

3

2

GND
DIG

2

C
S

1

S
L

M
A

1

2

3

4

L GND R

Power

39

2

Pin 20 keyed (removed)

C
S

S
L

M
A

4

1

40

R GND L

Digital Analog
Audio Audio
1

Host Interface

3

2

1

+5V GND +12V

Host Interface

Power

39

1

40

2

1

2

3

4

+12V GND +5V

Pin 20 keyed (removed)

Figure 17 - CD-ROM Connectors (Rear View)

11.1 CD-ROM Digital Audio Connector (Optional)
The CD-ROM Digital Audio Connector is an optional two-conductor shroud keyed header (Molex 70553 “G” or equivalent) which can be used to send audio to the host in a digital serial format. The pin assignments are shown in "Figure 17
- CD-ROM Connectors (Rear View)". The logic levels on this connector are standard CMOS and shall not exceed +5%
of the 5v supply. Recommended part numbers for the mating connector to 18 AWG cable are shown, but equivalent parts
may be used.
Mating Connectors: Molex 70066 “C(No Latch)” or “G(Latch)”, 70400 “C” or “G” and 70430 “C” or “G” or equivalent.
The serial format of the audio data is defined in EIAJ (Electronic Industry Association of Japan) document IEC-958.
IEC-958 has two parts. One is for professional use that is similar to the AES/EBU(Audio Engineering Society / European Broadcast Union). The other part is for consumer use and is the same as the Sony/Philips Digital Signal format. When
referring to EIAJ, specify which part is supported.

11.2 CD-ROM Analog Audio Connector (Optional)
The CD-ROM Analog Audio Connector is an optional four-conductor shroud keyed header (Molex 70553 “G” or equivalent) which can be used to send audio to the host in an analog format. The pin assignments are shown in "Figure 17 CD-ROM Connectors (Rear View)". The analog voltage levels on this connector shall not exceed 1.0V RMS. Recommended part numbers for the mating connector to 18 AWG cable are shown, but equivalent parts may be used.
Mating Connectors: Molex 70066 “C(No Latch)” or “G(Latch)”, 70400 “C” or “G” and 70430 “C” or “G” or equivalent.

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ATAPI Packet Commands for CD-ROM devices
Device Configuration Jumper (Optional)

11.3 Device Configuration Jumper (Optional)
The device configuration jumper is a 6-pin, unshrouded header (Molex 70203 or equivalent) as shown in "Figure 17 CD-ROM Connectors (Rear View)" with three marked positions (CS, SL, and MA). When a shorting jumper is placed in
the “CS” (CSEL) position the device shall use the “MA” (Master) or “SL” (Slave) jumper positions to configure the device. When the “CS” jumper is removed and placed such that both “SL” and “MA” are jumpered, the device shall use the
host interface signal CSEL to configure the device. The device configuration jumpers shall be accessible from the rear of
the drive.

C S M
S L A

C S M
S L A

C S M
S L A

C S M
S L A
Drive CSEL

Use CSEL

Master

Slave
Cable CSEL

Gnd

Vcc

Figure 18 - Device Configuration Jumper

11.4 Host IDE Interface Connector
The I/O connector is a 40-pin connector as shown in Figure 4 (ATA specification), with pin assignments as shown in Table 4 (ATA specification). The connector should be keyed to prevent the possibility of installing it upside down. A key is
provided by the removal of pin 20. The corresponding pin on the cable connector should be plugged.
The pin locations are governed by the cable plug, not the receptacle. The way in which the receptacle is mounted on the
printed circuit board affects the pin positions, and pin 1 should remain in the same relative position. This means the pin
numbers of the receptacle may not reflect the conductor number of the plug. The header receptacle is not polarized, and
all the signals are relative to pin 20, which is keyed.
By using the plug positions as primary, a straight cable can connect drives. As shown in Figure 4 (ATA specification, conductor 1 on pin 1 of the plug has to be in the same relative position no matter what the receptacle numbering looks like. If
receptacle numbering was followed, the cable would have to twist 180 degrees between a drive with top-mounted receptacles, and a drive with bottom-mounted receptacles.

11.5 Power Connector
The power connector is a four-conductor male plug. The pin assignments are shown in "Figure 17 - CD-ROM Connectors (Rear View)". Recommended part numbers for the mating connector to 28 AWG cable are shown below, but equivalent parts may be used.
Connector (4-pin): AMP 1-480424-0 or equivalent.
Contacts (loose piece): AMP 60619-4 or equivalent.
Contacts (strip): AMP 61117-4 or equivalent.

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ATAPI CD-ROM Specification

Annex A Play CD Decoder Types & Formats
The EBU IEC958 Standard shall be used for the Digital Output Port.

Attach IEC958 here.

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ATAPI CD-ROM Specification

Annex B Connectors

70553 Series

Dimensions
Circuits
2
3
4

Dim. A

Dim. B

.100
2,54
.200
5,08
.300
7,62

.210
5,33
.320
8,13
.420
10,67

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ATAPI CD-ROM Specification

70066 Series
“C” Version

70066-G

Dimensions
Circuits
2
3
4

Page 206

Dim. A

Dim. B

.100
2,54
.200
5,08
.300
7,62

.199
5,05
.299
7,59
.399
10,13

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ATAPI CD-ROM Specification

70203 Series

Recommended PC Board
Hole Layout

Dimensions
Circuits
4
6

In the Far East, this product has different engineering and order numbers
Contact Factory for sales drawings for 70294-xxx

Dim. A

Dim. B

.100
2,54
.200
5,08

.190
4,83
.290
7,37

For circuit sized 8 through 80 add .100 or 2,54mm
for each additional pin position

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