Pdp8_doc Digital Equipment Corporation PDP 8 Pdp8 Doc
User Manual: Digital Equipment Corporation PDP-8 Simulator ation
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PDP-8 Simulator Usage
01-Dec-08
COPYRIGHT NOTICE
The following copyright notice applies to the SIMH source, binary, and documentation:
Original code published in 1993-2008, written by Robert M Supnik
Copyright (c) 1993-2008, Robert M Supnik
Permission is hereby granted, free of charge, to any person obtaining a copy of this
software and associated documentation files (the "Software"), to deal in the Software
without restriction, including without limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or
substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL ROBERT M SUPNIK BE LIABLE FOR
ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
Except as contained in this notice, the name of Robert M Supnik shall not be used in
advertising or otherwise to promote the sale, use or other dealings in this Software
without prior written authorization from Robert M Supnik.
1 Simulator Files .............................................................................................................3
2 PDP-8 Features ...........................................................................................................3
2.1 CPU ......................................................................................................................5
2.2 TSC8-75 ETOS Timeshare Control (TSC)............................................................6
2.3 Programmed I/O Devices .....................................................................................6
2.3.1 PC8E Paper Tape Reader (PTR) .................................................................. 6
2.3.2 PC8E Paper Tape Punch (PTP) ....................................................................7
2.3.3 KL8E Terminal Input (TTI) .............................................................................7
2.3.4 KL8E Terminal Output (TTO)......................................................................... 8
2.3.5 LE8E Line Printer (LPT).................................................................................8
2.3.6 DK8E Line-Frequency Clock (CLK) ............................................................... 9
2.3.7 KL8JA Additional Terminals (TTIX, TTOX).................................................... 9
2.3.8 TD8E/TU56 DECtape (TD)..........................................................................10
2.3.9 TA8E/TA60 Cassette Tape (CT)..................................................................11
2.4 Moving Head Disks.............................................................................................12
2.4.1 RK8E Cartridge Disk (RK) ...........................................................................12
2.4.2 RL8A Cartridge Disk (RL) ............................................................................ 12
2.5 RX8E/RX01, RX28/RX02 Floppy Disk (RX) ....................................................... 13
2.6 Fixed Head Disks................................................................................................14
2.6.1 RF08/RS08 Fixed Head Disk (RF) ..............................................................14
2.6.2 DF32/DS32 Fixed Head Disk (RF) ..............................................................15
2.7 TC08/TU56 DECtape (DT) .................................................................................16
2.8 TM8E Magnetic Tape (MT)................................................................................. 17
3 Symbolic Display and Input........................................................................................17
This memorandum documents the PDP-8 simulator.
1 Simulator Files
sim/ scp.h
sim_console.h
sim_defs.h
sim_fio.h
sim_rev.h
sim_sock.h
sim_tape.h
sim_timer.h
sim_tmxr.h
scp.c
sim_console.c
sim_fio.c
sim_sock.c
sim_tape.c
sim_timer.c
sim_tmxr.c
sim/pdp8/ pdp8_defs.h
pdp8_cpu.c
pdp8_ct.c
pdp8_df.c
pdp8_dt.c
pdp8_lp.c
pdp8_mt.c
pdp8_pt.c
pdp8_rf.c
pdp8_rk.c
pdp8_rl.c
pdp8_rx.c
pdp8_sys.c
pdp8_td.c
pdp8_tsc.c
pdp8_tt.c
pdp8_ttx.c
2 PDP-8 Features
The PDP-8 simulator is configured as follows:
device names(s) simulates
CPU PDP-8/E CPU with 4KW-32KW of memory
- KE8E extended arithmetic element (EAE)
- KM8E memory management and timeshare control
TSC TSC8-75 ETOS operating system timeshare control
PTR,PTP PC8E paper tape reader/punch
TTI,TTO KL8E console terminal
TTIX,TTOX KL8JA additional terminals
LPT LE8E line printer
CLK DK8E line frequency clock (also PDP-8/A compatible)
RK RK8E/RK05 cartridge disk controller with four drives
RF RF08/RS08 fixed head disk controller with 1-4 platters
DF DF32/DS32 fixed head disk controller with 1-4 platters
RL RL8A/RL01 cartridge disk controller with four drives
RX RX8E/RX01, RX28/RX02 floppy disk controller with two
drives
DT TC08/TU56 DECtape controller with eight drives
TD TD8E/TU56 DECtape controller with two drives
MT TM8E/TU10 magnetic tape controller with eight drives
CT TA8E/TU60 cassette tape controller with two drives
Most devices can be disabled or enabled, by the commands:
SET <dev> DISABLED
SET <dev> ENABLED
The simulator allows most device numbers to be changed, by the command:
SET <dev> DEV=<number>
The PDP-8 can support only one of the set {DF32, RF08, RL8A} using the default device numbers, since
they all use device numbers 60-61. The default is the RF08. To change the disk at device numbers 60-61:
SET RF DISABLED disable RF08
SET DF ENABLED, or enable DF32
SET RL ENABLED enable RL8A
The PDP-8 can only support one of the set {TC08, TD8E} using the default device numbers, since both use
device number 77. The default is the TC08. To change the DECtape controller to the TD8E:
SET DT DISABLED disable TC08
SET TD ENABLED enable TD8E
The PDP-8 can only support one of the set {TM8E, TA8E} using the default device numbers, since both use
device number 70. The default is the TM8E. To change the device at device number 70:
SET MT DISABLED disable TM8E
SET CT ENABLED enable TA8E
Alternately, the device conflict can be eliminated by changing device numbers:
SET RL DEV=50
SET RL ENA
SET TD DEV=74
SET TD ENA
SET CT DEV=73
SET CT ENA
However, devices can only be BOOTed with their default device numbers.
The PDP-8 simulator implements several unique stop conditions:
- If an undefined instruction (unimplemented IOT or OPR) is decoded, and STOP_INST is set
- If a simulated DECtape runs off the end of its reel
The LOAD command supports both RIM format and BIN format tapes. If the file extension is .RIM, or the r
switch is specified with LOAD, the file is assumed to be RIM format; if the file extension is not .RIM, or the -b
switch is specified, the file is assumed to be BIN format.
2.1 CPU
The only CPU options are the presence of the EAE and the size of main memory; the memory extension
and time-share control is always included, even if memory size is 4K.
SET CPU EAE enable EAE
SET CPU NOEAE disable EAE
SET CPU 4K set memory size = 4K
SET CPU 8K set memory size = 8K
SET CPU 12K set memory size = 12K
SET CPU 16K set memory size = 16K
SET CPU 20K set memory size = 20K
SET CPU 24K set memory size = 24K
SET CPU 28K set memory size = 28K
SET CPU 32K set memory size = 32K
If memory size is being reduced, and the memory being truncated contains non-zero data, the simulator
asks for confirmation. Data in the truncated portion of memory is lost. Initial memory size is 32K.
CPU registers include the visible state of the processor as well as the control registers for the interrupt
system.
name size comments
PC 15 program counter, including IF as high 3 bits
AC 12 accumulator
MQ 12 multiplier-quotient
L 1 link
SR 12 front panel switches
IF 3 instruction field
DF 3 data field
IB 3 instruction field buffer
SF 7 save field
UF 1 user mode flag
UB 1 user mode buffer
SC 5 EAE shift counter
GTF 1 EAE greater than flag
EMODE 1 EAE mode (0 = A, 1 = B)
ION 1 interrupt enable
ION_DELAY 1 interrupt enable delay for ION
CIF_DELAY 1 interrupt enable delay for CIF
PWR_INT 1 power fail interrupt
UF_INT 1 user mode violation interrupt
INT 15 interrupt pending flags
DONE 15 device done flags
ENABLE 15 device interrupt enable flags
PCQ[0:63] 15 PC prior to last JMP, JMS, or interrupt;
most recent PC change first
STOP_INST 1 stop on undefined instruction
WRU 8 interrupt character
The CPU attempts to detect when the simulator is idle. When idle, the simulator does not use any resources
on the host system. Idle detection is controlled by the SET IDLE and SET NOIDLE commands:
SET CPU IDLE enable idle detection
SET CPU NOIDLE disable idle detection
Idle detection is disabled by default. At present, the CPU is considered idle if it is executing a KSF/JMP *-1
loop with interrupts disabled (OS/8, DMS-8) or a JMP * loop (TSS/8).
The CPU can maintain a history of the most recently executed instructions. This is controlled by the SET
CPU HISTORY and SHOW CPU HISTORY commands:
SET CPU HISTORY clear history buffer
SET CPU HISTORY=0 disable history
SET CPU HISTORY=n enable history, length = n
SHOW CPU HISTORY print CPU history
SHOW CPU HISTORY=n print first n entries of CPU history
The maximum length for the history is 65536 entries.
2.2 TSC8-75 ETOS Timeshare Control (TSC)
ETOS is a timeshared operating system for the PDP-8, providing multiple virtual OS/8 environments for up
to 32 users. It requires a special timeshare control option, the TSC8-75. The TSC8-75 is normally disabled;
to run ETOS, it must be enabled with the command:
SET TSC ENABLED
The TSC8-75 implements these registers:
name size comments
IR 12 most recently trapped instruction
PC 12 PC of most recently trapped instruction
CDF 1 1 if trapped instruction is CDF, 0 otherwise
ENB 1 interrupt enable flag
INT 1 interrupt pending flag
Except for operation of ETOS, the TSC8-75 should be left disabled.
2.3 Programmed I/O Devices
2.3.1 PC8E Paper Tape Reader (PTR)
The paper tape reader (PTR) reads data from a disk file. The POS register specifies the number of the next
data item to be read. Thus, by changing POS, the user can backspace or advance the reader.
The paper tape reader supports the BOOT command. BOOT PTR copies the RIM loader into memory and
starts it running.
The paper tape reader implements these registers:
name size comments
BUF 8 last data item processed
DONE 1 device done flag
ENABLE 1 interrupt enable flag
INT 1 interrupt pending flag
POS 32 position in the input file
TIME 24 time from I/O initiation to interrupt
STOP_IOE 1 stop on I/O error
Error handling is as follows:
error STOP_IOE processed as
not attached 1 report error and stop
0 out of tape
end of file 1 report error and stop
0 out of tape
OS I/O error x report error and stop
2.3.2 PC8E Paper Tape Punch (PTP)
The paper tape punch (PTP) writes data to a disk file. The POS register specifies the number of the next
data item to be written. Thus, by changing POS, the user can backspace or advance the punch.
The paper tape punch implements these registers:
name size comments
BUF 8 last data item processed
DONE 1 device done flag
ENABLE 1 interrupt enable flag
INT 1 interrupt pending flag
POS 32 position in the output file
TIME 24 time from I/O initiation to interrupt
STOP_IOE 1 stop on I/O error
Error handling is as follows:
error STOP_IOE processed as
not attached 1 report error and stop
0 out of tape
OS I/O error x report error and stop
2.3.3 KL8E Terminal Input (TTI)
The terminal interfaces (TTI, TTO) can be set to one of four modes, KSR, 7B, 7B, or 8B:
mode input characters output characters
KSR lower case converted lower case converted to upper case,
to upper case, high-order bit cleared,
high-order bit set non-printing characters suppressed
7P high-order bit cleared high-order bit cleared,
non-printing characters suppressed
7B high-order bit cleared high-order bit cleared
8B no changes no changes
The default mode is KSR.
The terminal input (TTI) polls the console keyboard for input. It implements these registers:
name size comments
BUF 8 last data item processed
DONE 1 device done flag
ENABLE 1 interrupt enable flag
INT 1 interrupt pending flag
POS 32 number of characters input
TIME 24 input polling interval (if 0, the keyboard
is polled synchronously with the clock)
2.3.4 KL8E Terminal Output (TTO)
The terminal output (TTO) writes to the simulator console window. It implements these registers:
name size comments
BUF 8 last data item processed
DONE 1 device done flag
ENABLE 1 interrupt enable flag
INT 1 interrupt pending flag
POS 32 number of characters output
TIME 24 time from I/O initiation to interrupt
2.3.5 LE8E Line Printer (LPT)
The line printer (LPT) writes data to a disk file. The POS register specifies the number of the next data item
to be read or written. Thus, by changing POS, the user can backspace or advance the printer.
The line printer implements these registers:
name size comments
BUF 8 last data item processed
ERR 1 error status flag
DONE 1 device done flag
ENABLE 1 interrupt enable flag
INT 1 interrupt pending flag
POS 32 position in the output file
TIME 24 time from I/O initiation to interrupt
Error handling is as follows:
error STOP_IOE processed as
not attached 1 report error and stop
0 out of paper
OS I/O error x report error and stop
2.3.6 DK8E Line-Frequency Clock (CLK)
The real-time clock (CLK) frequency can be adjusted as follows:
SET CLK 60HZ set frequency to 60Hz
SET CLK 50HZ set frequency to 50Hz
The default is 60Hz.
The clock implements these registers:
name size comments
DONE 1 device done flag
ENABLE 1 interrupt enable flag
INT 1 interrupt pending flag
TIME 24 clock interval
The real-time clock autocalibrates; the clock interval is adjusted up or down so that the clock tracks actual
elapsed time.
2.3.7 KL8JA Additional Terminals (TTIX, TTOX)
The additional terminals consist of two independent devices, TTIX and TTOX. The entire set is modeled as
a terminal multiplexer, with TTIX as the master controller. The additional terminals perform input and output
through Telnet sessions connected to a user-specified port. The ATTACH command specifies the port to be
used:
ATTACH TTIX <port> set up listening port
where port is a decimal number between 1 and 65535 that is not being used for other TCP/IP activities.
The additional terminals can be set to one of four modes: UC, 7P, 7B, or 8B.
mode input characters output characters
UC lower case converted lower case converted to upper case,
to upper case, high-order bit cleared,
high-order bit cleared non-printing characters suppressed
7P high-order bit cleared high-order bit cleared,
non-printing characters suppressed
7B high-order bit cleared high-order bit cleared
8B no changes no changes
The default mode is UC. Finally, each line supports output logging. The SET TTOXn LOG command
enables logging on a line:
SET TTOXn LOG=filename log output of line n to filename
The SET TTOXn NOLOG command disables logging and closes the open log file, if any.
Once TTIX is attached and the simulator is running, the terminals listen for connections on the specified
port. They assume that the incoming connections are Telnet connections. The connections remain open
until disconnected either by the Telnet client, a SET TTIX DISCONNECT command, or a DETACH TTIX
command.
Other special commands:
SHOW TTIX CONNECTIONS show current connections
SHOW TTIX STATISTICS show statistics for active connections
SET TTOXn DISCONNECT disconnects the specified line.
The input device (TTIX) implements these registers:
name size comments
BUF[0:3] 8 input buffer, lines 0 to 3
DONE 4 device done flags (line 0 rightmost)
ENABLE 4 interrupt enable flag
INT 4 interrupt pending flag
TIME 24 initial polling interval
TPS 10 polls per second after calibration
The output device (TTOX) implements these registers:
name size comments
BUF[0:3] 8 last data item processed, lines 0-3
DONE 4 device done flag (line 0 rightmost)
ENABLE 4 interrupt enable flag
INT 4 interrupt pending flag
TIME[0:3] 24 time from I/O initiation to interrupt,
lines 0-3
The additional terminals do not support save and restore. All open connections are lost when the simulator
shuts down or TTIX is detached.
2.3.8 TD8E/TU56 DECtape (TD)
The TD8E is a programmed I/O, non-interrupt controller, supporting two DECtape drives (0 and 1). The
TD8E simulator puts a high burden on the host processor, because tape activity is simulated a line (3b) at a
time. Unless the PDP-8 software requires the TD8E, the TC08 should be used to simulate DECtapes. The
TD8E is disabled by default.
TD8E options include the ability to make units write enabled or write locked.
SET TDn LOCKED set unit n write locked
SET TDn WRITEENABLED set unit n write enabled
Units can also be set ENABLED or DISABLED. The TD8E supports the BOOT command, but only for unit 0.
The TD8E supports supports PDP-8 format, PDP-11 format, and 18b format DECtape images. ATTACH
assumes the image is in PDP-8 format; the user can force other choices with switches:
-s PDP-11 format
-f 18b format
-a autoselect based on file on file size
The TD8E controller is a data-only simulator; the timing and mark track, and block header and trailer, are not
stored. Thus, read always produces standard values for mark track, header, and trailer words, and write
throws mark track, header, and trailer words into the bit bucket.
The TD8E controller implements these registers:
name size comments
TDCMD 4 command register
TDDAT 12 data register
TDMTK 6 mark track register
TDSLF 1 single line flag
TDQLF 1 quad line flag
TDTME 1 timing error flag
TDQL 2 quad line counter
LTIME 31 time between lines
DCTIME 31 time to decelerate to a full stop
POS[0:1] 32 position, in lines, units 0 and 1
STATT[0:1] 18 unit state, units 0 and 1
STOP_OFFR 1 stop on off-reel error
The LTIME parameter should not be changed, or OS/8 may fail to run correctly. The DCTIME parameter
should always be at least 100 times greater than LTIME. Acceleration time is 75% of deceleration time.
2.3.9 TA8E/TA60 Cassette Tape (CT)
The TA8E is a programmed I/O controller supporting two cassette drives (0 and 1). The TA8E can be used
with the MCPIP program under OS/8, and with the CAPS-8 operating system. Cassettes are simulated as
magnetic tapes with a fixed capacity (93,000 characters). The tape format is always SimH standard. The
TA8E is disabled by default.
TA8E options include the ability to make units write enabled or write locked.
SET CTn LOCKED set unit n write locked
SET CTn WRITEENABLED set unit n write enabled
Units cannot be set ENABLED or DISABLED. The TA8E supports the BOOT command, but only for CAPS-8,
and only for unit 0.
The TA8E controller implements these registers:
name size comments
CTSRA 8 status register A
CTSRB 8 status register B
CTDB 8 data buffer
CTDF 1 data flag
RDY 1 ready flag
WLE 1 write lock error
WRITE 1 TA60 write operation flag
INT 1 interrupt request
BPTR 17 buffer pointer
BLNT 17 buffer length
STIME 24 operation start time
CTIME 24 character latency
STOP_IOE 1 stop on I/O errors flag
POS[0:1] 32 position, units 0-1
Error handling is as follows:
error processed as
not attached tape not ready; if STOP_IOE, stop
end of file bad tape
OS I/O error CRC error; if STOP_IOE, stop
2.4 Moving Head Disks
2.4.1 RK8E Cartridge Disk (RK)
RK8E options include the ability to make units write enabled or write locked:
SET RKn LOCKED set unit n write locked
SET RKn WRITEENABLED set unit n write enabled
Units can also be set ENABLED or DISABLED. The RK8E supports the BOOT command.
The RK8E implements these registers:
name size comments
RKSTA 12 status
RKCMD 12 disk command
RKDA 12 disk address
RKMA 12 current memory address
BUSY 1 control busy flag
INT 1 interrupt pending flag
STIME 24 seek time, per cylinder
RTIME 24 rotational delay
STOP_IOE 1 stop on I/O error
Error handling is as follows:
error STOP_IOE processed as
not attached 1 report error and stop
0 disk not ready
end of file x assume rest of disk is zero
OS I/O error x report error and stop
2.4.2 RL8A Cartridge Disk (RL)
RL8A options include the ability to make units write enabled or write locked:
SET RLn LOCKED set unit n write locked
SET RLn WRITEENABLED set unit n write enabled
Units can also be set ENABLED or DISABLED. The RL8A supports the BOOT command, but only for unit 0.
The RL8A implements these registers:
name size comments
RLCSA 12 control/status A
RLCSB 12 control/status B
RLMA 12 memory address
RLWC 12 word count
RLSA 6 sector address
RLER 12 error flags
RLSI 16 silo top word
RLSI1 16 silo second word
RLSI2 16 silo third word
RLSIL 1 silo read left/right flag
INT 1 interrupt request
DONE 1 done flag
ERR 1 composite error flag
STIME 1 seek time, per cylinder
RTIME 1 rotational delay
STOP_IOE 1 stop on I/O error
Error handling is as follows:
error STOP_IOE processed as
not attached 1 report error and stop
0 disk not ready
end of file x assume rest of disk is zero
OS I/O error x report error and stop
2.5 RX8E/RX01, RX28/RX02 Floppy Disk (RX)
The RX can be configured as an RX8E with two RX01 drives, or an RX28 with two RX02 drives:
SET RX RX8E set controller to RX8E/RX01
SET RX RX28 set controller to RX28/RX02
The controller is set to the RX8E by default. The RX28 is not backwards-compatible with the RX8E and will
not work with the standard OS/8 V3D floppy disk driver.
RX8E options include the ability to set units write enabled or write locked:
SET RXn LOCKED set unit n write locked
SET RXn WRITEENABLED set unit n write enabled
RX28 options include, in addition, the ability to set the unit density to single density, double density, or
autosized; autosizing is the default:
SET RXn SINGLE set unit n single density
SET RXn DOUBLE set unit n double density
SET RXn AUTOSIZE set unit n autosize
The RX8E and RX28 support the BOOT command.
The RX8E and RX28 implement these registers:
name size comments
RXCS 12 status
RXDB 12 data buffer
RXES 12 error status
RXTA 8 current track
RXSA 8 current sector
STAPTR 4 controller state
BUFPTR 8 buffer pointer
INT 1 interrupt pending flag
DONE 1 device done flag
ENABLE 1 interrupt enable flag
TR 1 transfer ready flag
ERR 1 error flag
CTIME 24 command completion time
STIME 24 seek time, per track
XTIME 24 transfer ready delay
STOP_IOE 1 stop on I/O error
SBUF[0:255] 8 sector buffer array
Error handling is as follows:
error STOP_IOE processed as
not attached 1 report error and stop
0 disk not ready
RX01 and RX02 data files are buffered in memory; therefore, end of file and OS I/O errors cannot occur.
2.6 Fixed Head Disks
With default device addressing, either the RF08 or the DF32 can be present in a configuration, but not both.
2.6.1 RF08/RS08 Fixed Head Disk (RF)
RF08 options include the ability to set the number of platters to a fixed value between 1 and 4, or to autosize
the number of platters:
SET RF 1P one platter (256K)
SET RF 2P two platters (512K)
SET RF 3P three platters (768K)
SET RF 4P four platters (1024K)
SET RF AUTOSIZE autosized on ATTACH
The default is one platter.
The RF08 implements these registers:
name size comments
STA 12 status
DA 20 current disk address
MA 12 memory address (in memory)
WC 12 word count (in memory)
WLK 32 write lock switches
INT 1 interrupt pending flag
DONE 1 device done flag
TIME 24 rotational delay, per word
BURST 1 burst flag
STOP_IOE 1 stop on I/O error
The RF08 supports the BOOT command. The default bootstrap is for OS/8. To bootstrap the 4K Disk
Monitor, use the BOOT -D RF command.
The RF08 is a three-cycle data break device. If BURST = 0, word transfers are scheduled individually; if
BURST = 1, the entire transfer occurs in a single data break.
Error handling is as follows:
error STOP_IOE processed as
not attached 1 report error and stop
0 disk not ready
RF08 data files are buffered in memory; therefore, end of file and OS I/O errors cannot occur.
2.6.2 DF32/DS32 Fixed Head Disk (RF)
DF32 options include the ability to set the number of platters to a fixed value between 1 and 4, or to autosize
the number of platters:
SET DF 1P one platter (32K)
SET DF 2P two platters (64K)
SET DF 3P three platters (98K)
SET DF 4P four platters (128K)
SET DF AUTOSIZE autosized on ATTACH
The default is one platter.
The DF32 implements these registers:
name size comments
STA 12 status, disk and memory address extension
DA 12 low order disk address
MA 12 memory address (in memory)
WC 12 word count (in memory)
WLK 16 write lock switches
INT 1 interrupt pending flag
DONE 1 device done flag
TIME 24 rotational delay, per word
BURST 1 burst flag
STOP_IOE 1 stop on I/O error
The DF32 supports the BOOT command. The default bootstrap is for OS/8. To bootstrap the 4K Disk
Monitor, use the BOOT -D DF command.
The DF32 is a three-cycle data break device. If BURST = 0, word transfers are scheduled individually; if
BURST = 1, the entire transfer occurs in a single data break.
Error handling is as follows:
error STOP_IOE processed as
not attached 1 report error and stop
0 disk not ready
DF32 data files are buffered in memory; therefore, end of file and OS I/O errors cannot occur.
2.7 TC08/TU56 DECtape (DT)
DECtapes drives are numbered 1-8; in the simulator, drive 8 is unit 0. TC08 options include the ability to
make units write enabled or write locked.
SET DTn LOCKED set unit n write locked
SET DTn WRITEENABLED set unit n write enabled
Units can also be set ENABLED or DISABLED. The TC08 supports the BOOT command, but only for unit 0.
The TC08 supports supports PDP-8 format, PDP-11 format, and 18b format DECtape images. ATTACH
assumes the image is in PDP-8 format; the user can force other choices with switches:
-s PDP-11 format
-f 18b format
-a autoselect based on file on file size
The TC08 controller is a data-only simulator; the timing and mark track, and block header and trailer, are not
stored. Thus, the WRITE TIMING AND MARK TRACK function is not supported; the READ ALL function
always returns the hardware standard block header and trailer; and the WRITE ALL function dumps non-
data words into the bit bucket.
The DECtape controller implements these registers:
name size comments
DTSA 12 status register A
DTSB 12 status register B
INT 1 interrupt pending flag
ENB 1 interrupt enable flag
DTF 1 DECtape flag
ERF 1 error flag
CA 12 current address (memory location 7754)
WC 12 word count (memory location 7755)
LTIME 31 time between lines
DCTIME 31 time to decelerate to a full stop
SUBSTATE 2 read/write command substate
POS[0:7] 32 position, in lines, units 0 to 7
STATT[0:7] 31 unit state, units 0 to 7
STOP_OFFR 1 stop on off-reel error
It is critically important to maintain certain timing relationships among the DECtape parameters, or the
DECtape simulator will fail to operate correctly.
- LTIME must be at least 6
- DCTIME needs to be at least 100 times LTIME
Acceleration time is set to 75% of deceleration time.
2.8 TM8E Magnetic Tape (MT)
Magnetic tape options include the ability to make units write enabled or write locked.
SET MTn LOCKED set unit n write locked
SET MTn WRITEENABLED set unit n write enabled
Magnetic tape units can be set to a specific reel capacity in MB, or to unlimited capacity:
SET MTn CAPAC=m set unit n capacity to m MB (0 = unlimited)
SHOW MTn CAPAC show unit n capacity in MB
Units can also be set ENABLED or DISABLED.
The magnetic tape controller implements these registers:
name size comments
CMD 12 command
FNC 12 function
CA 12 memory address
WC 12 word count
DB 12 data buffer
STA 12 main status
STA2 6 secondary status
DONE 1 device done flag
INT 1 interrupt pending flag
STOP_IOE 1 stop on I/O error
TIME 24 record delay
UST[0:7] 24 unit status, units 0 to 7
POS[0:7] 32 position, units 0 to 7
Error handling is as follows:
error processed as
not attached tape not ready; if STOP_IOE, stop
end of file bad tape
OS I/O error parity error; if STOP_IOE, stop
3 Symbolic Display and Input
The PDP-8 simulator implements symbolic display and input. Display is controlled by command line
switches:
-a display as ASCII character
-c display as two packed sixbit characters
-t display as two packed TSS/8 sixbit characters
-m display instruction mnemonics
Input parsing is controlled by the first character typed in or by command line switches:
' or -a ASCII character
" or -c two packed sixbit characters
# or -t two packed TSS/8 sixbit characters
alphabetic instruction mnemonic
numeric octal number
Instruction input uses standard PDP-8 assembler syntax. There are four instruction classes: memory
reference, IOT, field change, and operate.
Memory reference instructions have the format
memref {I} {C/Z} address
where I signifies indirect, C a current page reference, and Z a zero page reference. The address is an octal
number in the range 0 - 07777; if C or Z is specified, the address is a page offset in the range 0 - 177.
Normally, C is not needed; the simulator figures out from the address what mode to use. However, when
referencing memory outside the CPU (eg, disks), there is no valid PC, and C must be used to specify current
page addressing.
IOT instructions consist of single mnemonics, eg, KRB, TLS. IOT instructions may be or'd together
iot iot iot...
The simulator does not check the legality of the proposed combination. IOT's for which there is no opcode
may be specified as IOT n, where n is an octal number in the range 0 - 0777.
Field change instructions (CIF, CDF) have the format
fldchg field
where field is an octal number in the range 0 - 7. Field change instructions may be or'd together.
Operate instructions have the format
opr opr opr...
The simulator does not check the legality of the proposed combination. EAE mode A and B mnemonics
may be specified regardless of the EAE mode. The operands for MUY and DVI must be deposited explicitly.
