To: Users From: Bob Supnik Subj: IBM 1401 Simulator Usage Date: 15-Jan-2002 COPYRIGHT NOTICE The following copyright notice applies to both the SIMH source and binary: Original code published in 1993-2002, written by Robert M Supnik Copyright (c) 1993-2002, 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 IBM 1401 simulator. 1. Simulator Files sim/ sim_defs.h scp.c scp_tty.c sim_rev.c sim/i1401/ i1401_defs.h i1401_cpu.c i1401_iq.c i1401_lp.c i1401_mt.c i1401_sys.c 2. IBM 1401 Features The IBM 1401 simulator is configured as follows: device simulates name(s) CPU IBM 1401 CPU with 16K of memory CDR,CDP IBM 1402 card reader/punch LPT IBM 1403 line printer INQ IBM 1407 inquiry terminal MT IBM 729 7-track magnetic tape controller with six drives The IBM 1401 simulator implements many unique stop conditions. On almost any kind of error the simulator stops: unimplemented opcode reference to non-existent memory reference to non-existent device no word mark under opcode invalid A address invalid B address invalid instruction length invalid modifier character invalid branch address invalid magtape unit number invalid magtape record length write to locked magtape drive skip to unpunched carriage control tape channel card reader hopper empty address register wrap-around single character A field in MCE single character B field in MCE hanging $ in MCE with EPE enabled I/O check with I/O stop switch set The LOAD and DUMP commands are not implemented. 2.1 CPU The CPU options include a number of special features and the size of main memory. Note that the Modify Address special feature is always included when memory size is greater than 4K. SET CPU XSA enable advanced programming special feature SET CPU NOXSA disable advanced programming SET CPU HLE enable high/low/equal special feature SET CPU NOHLE disable high/low/equal SET CPU BBE enable branch on bit equal special feature SET CPU NOBBE disable branch on bit equal SET CPU MR enable move record special feature SET CPU NOMR disable move record SET CPU EPE enable extended print edit special feature SET CPU NOEPE disable extended print edit 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 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. Initially, memory size is 16K, and all special features are enabled. Memory is implemented as 7 bit BCD characters, as follows: 6 5 4 3 2 1 0 word B bit A bit 8 4 2 1 mark <-- zone --> <-------- digit --------> In BCD, the decimal digits 0-9 are (octal) values 012, 001, 002, 003, 004, 005, 006, 007, 010, 011, respectively. Signs are encoded in the zone bits, with 00, 01, and 11 being positive, and 10 being negative. CPU registers include the visible state of the processor. The 1401 has no interrupt system. name size comments IS 14 instruction storage address register (PC) AS 14 A storage address register BS 14 B storage address register ASERR 1 AS invalid flag BSERR 1 BS invalid flag SSA 1 sense switch A SSB 1 sense switch B SSC 1 sense switch C SSD 1 sense switch D SSE 1 sense switch E SSF 1 sense switch F SSG 1 sense switch G EQU 1 equal compare indicator UNEQ 1 unequal compare indicator HIGH 1 high compare indicator LOW 1 low compare indicator OVF 1 overflow indicator IOCHK 1 I/O check switch PRCHK 1 process check switch ISQ 1 IS prior to last branch; most recent IS change first WRU 8 interrupt character 2.2 1402 Card Reader/Punch (CDR, CDP, STKR) The IBM 1402 card/reader punch is simulated as three independent devices: the card reader (CDR), the card punch (CDP), and the reader and punch stackers (STKR). STRK units 0, 1, 2, and 4 correspond to the reader normal stacker, reader stacker 1, shared stacker 2/8, and punch stacker 4, respectively. The card reader supports the BOOT command. BOOT CDR reads a card image into locations 1-80, sets a word mark under location 1, clears storage, and then transfers control to location 1. The card reader reads data from disk files, while the punch and stackers write data to disk files. Cards are simulated as ASCII text lines with terminating newlines; column binary is not supported. For each unit, 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 these devices. The reader/punch registers are: device name size comments CDR LAST 1 last card indicator ERR 1 error indicator S1 1 stacker 1 select flag S2 1 stacker 2 select flag POS 31 position TIME 24 delay window for stacker select BUF[0:79] 8 reader buffer CDP ERR 1 error indicator S4 1 stacker 4 select flag S8 1 stacker 8 select flag STKR POS0 31 position, normal reader stack POS1 31 position, reader stacker 1 POS2 31 position, shared stacker 2/8 POS4 31 position, punch stacker 4 Error handling is as follows: device error processed as reader end of file if SSA set, set LAST indicator on next Read, report error and stop reader,punch not attached report error and stop OS I/O error print error message if IOCHK set, report error and stop otherwise, set ERR indicator stacker not attached ignored OS I/O error print error message if IOCHK set, report error and stop 2.3 1403 Line Printer (LPT) The IBM 1403 line printer (LPT) writes its data, converted to ASCII, to a disk file. The line printer supports three different print character sets or "chains": SET LPT PCF full 64 character chain SET LPT PCA 48 character business chain SET LPT PCH 48 character FORTRAN chain In addition, the line printer can be programmed with a carriage control tape. The LOAD command loads a new carriage control tape: LOAD load carriage control tape file The format of a carriage control tape consists of multiple lines. Each line contains an optional repeat count, enclosed in parentheses, optionally followed by a series of column numbers separated by commas. Column numbers must be between 1 and 12; a column number of zero denotes top of form. The following are all legal carriage control specifications: no punch (5) 5 lines with no punches 1,5,7,8 columns 1, 5, 7, 8 punched (10)2 10 lines with column 2 punched 1,0 column 1 punched; top of form The default form is 66 lines long, with column 1 and the top of form mark on line 1, and the rest blank. The line printer registers are: name size comments LINES 8 number of newlines after next print LFLAG 1 carriage control flag (1 = skip, 0 = space) CCTP 8 carriage control tape pointer CCTL 8 carriage control tape length (read only) ERR 1 error indicator POS 31 position CCT[0:131] 32 carriage control tape array Error handling is as follows: error processed as not attached report error and stop OS I/O error print error message if IOCHK set, report error and stop otherwise, set ERR indicator 2.4 1407 Inquiry Terminal (INQ) The IBM 1407 inquiry terminal (INQ) is a half-duplex console. It polls the console keyboard periodically for inquiry requests. The inquiry terminal registers are: name size comments INQC 7 inquiry request character (initially ESC) INR 1 inquiry request indicator INC 1 inquiry cleared indicator TIME 24 polling interval When the 1401 CPU requests input from the keyboard, the message [Enter] is printed out, followed by a new line. The CPU hangs waiting for input until either the return/enter key is pressed, or the inquiry request character is typed in. The latter cancels the type-in and sets INC. The inquiry terminal has no errors. 2.5 729 Magnetic Tape (MT) The magnetic tape controller supports six drives, numbered 1 through 6. 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 ONLINE or OFFLINE. The magnetic tape simulator supports the BOOT command. BOOT MT reads the first record off tape, starting at location 1, and then branches to it. The magnetic tape controller implements these registers: name size comments END 1 end of file indicator ERR 1 error indicator PAR 1 parity error indicator POS1..6 31 position, drives 1..6 Error handling is as follows: error processed as not attached report error and stop end of file (read or space) end of physical tape (write) ignored OS I/O error print error message if IOCHK set, report error and stop otherwise, set ERR indicator 2.6 Symbolic Display and Input The IBM 1401 simulator implements symbolic display and input. Display is controlled by command line switches: -c display as single character (BCD for CPU and MT, ASCII for others) -s display as wordmark terminated BCD string (CPU only) -m display instruction mnemonics (CPU only) In a CPU character display, word marks are denoted by ~. Input parsing is controlled by the first character typed in or by command line switches: ' or " or -c or -s characters (BCD for CPU and MT, ASCII for others) alphabetic instruction mnemonic numeric octal number Instruction input is free format, with spaces separating fields. There are six instruction formats: 1, 2, 4, 5, 7, and 8 characters: 1 character opcode 2 character opcode 'modifier 4 character opcode address 5 character opcode address 'modifier 7 character opcode address address 8 character opcode address address 'modifier Addresses are always decimal, except for special I/O addresses in the A field, which may be specified as %xy, where x denotes the device and y the unit number. For the CPU, string input may encompass multiple characters. A word mark is denoted by ~ and must precede the character to be marked. All other devices can only accept single character input, without word marks. 2.7 Character Sets The IBM 1401 used a 6b character code called BCD (binary coded decimal). Some of the characters have no equivalent in ASCII and require different representations: BCD ASCII IBM 1401 print code representation character chains 00 space 01 1 02 2 03 3 04 4 05 5 06 6 07 7 10 8 11 9 12 0 13 # = in H chain 14 @ ' in H chain 15 : blank in A, H chains 16 > blank in A, H chains 17 ( tape mark blank in A, H chains 20 ^ alternate blank blank in A, H chains 21 / 22 S 23 T 24 U 25 V 26 W 27 X 30 Y 31 Z 32 ' record mark 33 , 34 % ( in H chain 35 = word mark blank in A, H chains 36 \ blank in A, H chains 37 + blank in A, H chains 40 - 41 J 42 K 43 L 44 M 45 N 46 O 47 P 50 Q 51 R 52 ! 53 $ 54 * 55 ] blank in A, H chains 56 ; blank in A, H chains 57 _ delta blank in A, H chains 60 & 61 A 62 B 63 C 64 D 65 E 66 F 67 G 70 H 71 I 72 ? 73 . 74 ) lozenge 75 [ blank in A, H chains 76 < blank in A, H chains 77 " group mark blank in A, H chains