To: Users From: Bob Supnik Subj: PDP-8 Simulator Usage Date: 15-Nov-2004 COPYRIGHT NOTICE The following copyright notice applies to both the SIMH source and binary: Original code published in 1993-2004, written by Robert M Supnik Copyright (c) 1993-2004, 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. 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_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 simulates name(s) 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, or 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 Most devices can be disabled or enabled, by the commands: SET DISABLED SET ENABLED The simulator allows most device numbers to be changed, by the command: SET DEV= 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: sim> SET RF DISABLED disable RF08 sim> SET DF ENABLED, or enable DF32 sim> 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: sim> SET DT DISABLED disable TC08 sim> SET TD ENABLED enable TD8E Alternately, the device conflict can be eliminated by changing device numbers: sim> SET RL DEV=50 sim> SET RL ENA sim> SET TD DEV=74 sim> SET TD 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 register STOP_INST - if a simulated DECtape runs off the end of its reel The PDP-8 loader 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 if 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 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: IR most recently trapped instruction PC PC of most recently trapped instruction CDF 1 if trapped instruction is CDF, 0 otherwise ENB interrupt enable flag INT 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 bewritten. 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 three modes: KSR, 7B, or 8B. In KSR mode, lower case input and output characters are automatically converted to upper case, and the high order bit is forced to one on input. In 7B mode, input and output characters are masked to 7 bits. In 8B mode, characters are not modified. Changing the mode of either interface changes both. 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 keyboard polling interval 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 set error flag 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 modelled as a terminal multiplexor, with TTIX as the master unit. 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 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 three modes: UC, 7B, or 8B. In UC mode, lower case input and output characters are converted automatically to upper case. In 7B mode, input and output characters are masked to 7 bits. In 8B mode, characters are not modified. 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 TTOXLn 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. The SHOW TTIX CONNECTIONS command displays the current connections to the extra terminals. The SHOW TTIX STATISTICS command displays statistics for active connections. The SET TTIX DISCONNECT=linenumber disconnects the specified line. The input device (TTIX) implements these registers: name size comments BUF[0:3] 8 input buffer, lines 0-3 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 DTn LOCKED set unit n write locked SET DTn WRITEENABLED set unit n write enabled Units can also be set ENABLED or DISABLED. The TD8E supports the BOOT command. The TD8E supports supports PDP-8 format, PDP-11 format, and 18b format DECtape images. ATTACH tries to determine the tape format from the DECtape image; the user can force a particular format with switches: -r PDP-8 format -s PDP-11 format -t 18b format 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 header and trailer words, and write throws 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[0:7] 32 position, in lines, units 0-7 STATT[0:7] 18 unit state, units 0-7 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. 2.4 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 ONLINE or OFFILE. The RL8A supports the BOOT command. 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 Either the RF08 or the DF32 can be present in a configuration, but not both, with default device addressing. 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 from the attached file: 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 from the attached file: 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. The TC08 supports supports PDP-8 format, PDP-11 format, and 18b format DECtape images. ATTACH tries to determine the tape format from the DECtape image; the user can force a particular format with switches: -r PDP-8 format -s PDP-11 format -t 18b format 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 0-7 STATT[0:7] 31 unit state, units 0-7 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 or write locked. SET MTn LOCKED set unit n write locked SET MTn WRITEENABLED set unit n write enabled 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 0-7 POS[0:7] 32 position, units 0-7 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 2.9 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 (sixbit) character string -t display as (TSS/8 sixbit) character string -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 character sixbit string # or -t two character TSS/8 sixbit string 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.