SDS/sds_doc.txt

To:	Users
From:	Bob Supnik
Subj:	SDS 940 Simulator Usage
Date:	01-Jul-2005

			COPYRIGHT NOTICE

The following copyright notice applies to both the SIMH source and binary:

   Original code published in 1993-2005, written by Robert M Supnik
   Copyright (c) 1993-2005, 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 SDS 940 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/sds/	sds_defs.h
		sds_cpu.c
		sds_drm.c
		sds_dsk.c
		sds_io.c
		sds_lp.c
		sds_mt.c
		sds_mux.c
		sds_rad.c
		sds_stddev.c
		sds_sys.c

2. SDS 940 Features

The SDS-940 simulator is configured as follows:

device		simulates
name(s)

CPU		SDS-940 CPU with 16KW to 64KW of memory
CHAN		I/O channels
PTR		paper tape reader
PTP		paper tape punch
TTI		console input
TTO		console output
LPT		line printer
RTC		real-time clock
MUX		terminal multiplexor
DRM		Project Genie drum
RAD		fixed head disk
DSK		9164/9165 rapid access (moving head) disk
MT		magnetic tape

Most devices can be disabled or enabled with the SET <dev> DISABLED and
SET <dev> ENABLED commands, respectively.

2.1 CPU

The CPU options set the size of main memory and the configuration of
peripherals.

	SET CPU 16K		set memory size = 16KW
	SET CPU 32K		set memory size = 32KW
	SET CPU 48K		set memory size = 48KW
	SET CPU 64K		set memory size = 64KW
	SET CPU GENIE		enable DRM, set terminal mux
				to GENIE mode
	SET CPU SDS		disable DRM, set terminal mux
				to SDS mode

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 64KW.

CPU registers include the visible state of the processor as well as the
control registers for the interrupt system.

	name		size	comments

	P		14	program counter
	A		24	accumulator A
	B		24	accumulator B
	X		24	index register
	OV		1	overflow indicator
	EM2		3	memory extension, quadrant 2
	EM3		3	memory extension, quadrant 3
	RL1		24	user relocation register 1
	RL2		24	user relocation register 2
	RL4		12	kernel relocation register
	NML		1	normal mode flag
	USR		1	user mode flag
	MONUSR		1	monitor-to-user trap enable
	ION		1	interrupt enable
	INTDEF		1	interrupt defer
	INTREQ		32	interrupt request flags
	APIACT		5	highest active API level
	APIREQ		5	highest requesting API level
	XFRREQ		32	device transfer request flags
	BPT		4	breakpoint switches
	ALERT		6	outstanding alert number
	STOP_INVINS	1	stop on invalid instruction
	STOP_INVDEV	1	stop on invalid device number
	STOP_INVIOP	1	stop on invalid I/O operation
	INDLIM		8	maximum indirect nesting depth
	EXULIM		8	maximum execute nesting depth
	PCQ[0:63]	14	P prior to last branch or interrupt;
				most recent P change first
	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 Channels (CHAN)

The SDS 940 has up to eight I/O channels, designated W, Y, C, D, E, F, G,
and H.  W, Y, C, and D are time-multiplexed communications channels (TMCC);
E, F, G, and H are direct access communications channels (DACC).  Unlike
real SDS 940 channels, the simulated channels handle 6b, 12b, and 24b transfers
simultaneously.  The association between a device and a channel is displayed
by the SHOW <dev> CHAN command:

	SIM> SHOW LPT CHAN
	channel=W

The user can change the association with the SET <dev> CHAN=<chan> command,
where <chan> is a channel letter:

	SIM> SET LPT CHAN=E
	SIM> SHOW LPT CHAN
	channel=E

Each channel has nine registers.  The registers are arrays, with entry [0]
for channel W, entry [1] for channel Y, etc.

	name		size	comments

	UAR[0:7]	6	unit address register
	WCR[0:7]	15	word count register
	MAR[0:7]	16	memory address register
	DCR[0:7]	6	data chaining register
	WAR[0:7]	24	word assembly register
	CPW[0:7]	2	characters per word
	CNT[0:7]	3	character count
	MODE[0:7]	12	channel mode (from EOM instruction)
	FLAG[0:7]	9	channel flags		

The user can display all the registers in a channel with the command:

	SHOW CHAN channel-letter

2.3 Console Input (TTI)

The console input (TTI) polls the console keyboard for input.  It
implements these registers:

	name		size	comments

	BUF		6	data buffer
	XFR		1	transfer ready flag
	POS		32	number of characters input
	TIME		24	polling interval

By default, the console input is assigned to channel W.

2.4 Console Output (TTO)

The console output (TTO) writes to the simulator console window.  It
implements these registers:

	name		size	comments

	BUF		6	data buffer
	XFR		1	transfer ready flag
	POS		32	number of characters input
	TIME		24	time from I/O initiation to interrupt

By default, the console output is assigned to channel W.

2.5 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 implements these registers:

	name		size	comments

	BUF		6	data buffer
	XFR		1	transfer ready flag
	SOR		1	start of record flag
	CHAN		4	active channel
	POS		32	number of characters input
	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

By default, the paper tape reader is assigned to channel W.

2.6 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 by changing POS, the user can backspace or advance the punch.

The paper tape punch implements these registers:

	name		size	comments

	BUF		6	data buffer
	XFR		1	transfer ready flag
	LDR		1	punch leader flag
	CHAN		4	active channel
	POS		32	number of characters input
	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

By default, the paper tape punch is assigned to channel W.

2.7 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 written.  Thus,
by changing POS, the user can backspace or advance the printer.

The line printer implements these registers:

	name		size	comments

	BUF[0:131]	8	data buffer
	BPTR		8	buffer pointer
	XFR		1	transfer ready flag
	ERR		1	error flag
	CHAN		4	active channel
	CCT[0:131]	8	carriage control tape
	CCTP		8	pointer into carriage control tape
	CCTL		8	length of carriage control tape
	SPCINST		24	spacing instruction
	POS		32	number of characters input
	CTIME		24	intercharacter time
	PTIME		24	print time
	STIME		24	space time
	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 paper

	OS I/O error	x	report error and stop

By default, the line printer is assigned to channel W.

2.8 Real-Time Clock (RTC)

The real-time clock (RTC) frequency can be adjusted as follows:

	SET RTC 60HZ		set frequency to 60Hz
	SET RTC 50HZ		set frequency to 50Hz

The default is 60Hz.

The clock implements these registers:

	name		size	comments

	PIE		1	interrupt enable
	TIME		24	tick interval

The real-time clock autocalibrates; the clock interval is adjusted up or
down so that the clock tracks actual elapsed time.

2.9 Terminal Multiplexor (MUX)

The terminal multiplexor provides 32 asynchronous interfaces.  In Genie
mode, the interfaces are hard-wired; in SDS mode, they implement modem
control.  The multiplexor has two controllers: MUX for the scanner, and
MUXL for the individual lines.  The terminal multiplexor performs input
and output through Telnet sessions connected to a user-specified port.
The ATTACH command specifies the port to be used:

	ATTACH MUX <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.

Each line (each unit of MUXL) supports one option: UC, when set, causes
lower case input characters to be automatically converted to upper case.
In addition, each line supports output logging.  The SET MUXLn LOG command
enables logging on a line:

	SET MUXLn filename	log output of line n to filename

The SET MUXLn NOLOG command disables logging and closes the open log
file, if any.

Once MUX is attached and the simulator is running, the multiplexor listens
for connections on the specified port.  It assumes that the incoming
connections are Telnet connections.  The connections remain open until
disconnected either by the Telnet client, a SET MUX DISCONNECT command,
or a DETACH MUX command.

The SHOW MUX CONNECTIONS command displays the current connections to the
extra terminals.  The SHOW MUX STATISTICS command displays statistics for
active connections.  The SET MUXLn DISCONNECT command disconnects line n.

The controller (MUX) implements these registers:

	name		size	comments

	STA[0:31]	6	status, lines 0 to 31
	RBUF[0:31]	8	receive buffer, lines 0 to 31
	XBUF[0:31]	8	transmit buffer, lines 0 to 31
	FLAGS[0:127]	1	line flags, 0 to 3 for line 0,
				4 to 7 for line 1, etc
	SCAN		7	scanner current flag number
	SLCK		1	scanner locked flag
	TPS		8	character polls per second

The lines (MUXL) implements these registers:

	name		size	comments

	TIME[0:31]	24	transmit time, lines 0 to 31

The terminal multiplexor does not support save and restore.  All open
connections are lost when the simulator shuts down or MUX is detached.

2.10 Project Genie Drum (DRM)

The Project Genie drum (DRM) implements these registers:

	name		size	comments

	DA		19	drum address
	CA		16	core address
	WC		14	word count
	PAR		12	cumulative sector parity
	RW		1	read/write flag
	ERR		1	error flag
	STA		2	drum state
	FTIME		24	channel program fetch time
	XTIME		24	interword transfer time
	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	drum not ready

Drum data files are buffered in memory; therefore, end of file and OS
I/O errors cannot occur.  Unlike conventional SDS 940 devices, the Project
Genie drum does not use a channel.

2.11 Rapid Access (fixed head) Disk (RAD)

The rapid access disk (RAD) implements these registers:

	name		size	comments

	DA		15	disk address
	SA		6	sector word address
	BP		1	sector byte pointer
	XFR		1	data transfer flag
	NOBD		1	inhibit increment across track
	ERR		1	error flag
	CHAN		4	active channel
	PROT		8	write protect switches
	TIME		24	interval between halfword transfers
	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

The rapid access disk is buffered in memory; end of file and OS I/O errors
cannot occur.  By default, the rapid access disk is assigned to channel E.

2.12 Moving Head Disk (DSK)

DSK options include the ability to make the drive write enabled or write
locked:

	SET RAD LOCKED		set write locked
	SET RAD WRITEENABLED	set write enabled

The moving head disk implements these registers:

	name		size	comments

	BUF[0:63]	8	transfer buffer
	BPTR		9	buffer pointer
	BLNT		9	buffer length
	DA		21	disk address
	INST		24	disk instruction
	XFR		1	data transfer flag
	ERR		1	error flag
	CHAN		4	active channel
	WTIME		24	interval between character transfers
	STIME		24	seek interval
	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


By default, the moving head disk is assigned to channel F.

2.13 Magnetic Tape (MT)

MT 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

Units can also be set ENABLED or DISABLED.

The magnetic tape implements these registers:

	name		size	comments

	BUF[0:131071]	8	transfer buffer
	BPTR		18	buffer pointer
	BLNT		18	buffer length
	XFR		1	data transfer flag
	CHAN		4	active channel
	INST		24	magtape instruction
	EOF		1	end-of-file flag
	GAP		1	inter-record gap flag
	SKIP		1	skip data flag
	CTIME		24	interval between character transfers
	GTIME		24	gap interval
	POS[0:7]	32	position, drives 0:7
	STOP_IOE	1	stop on I/O error

Error handling is as follows:

	error			processed as

	not attached		tape not ready; if STOP_IOE, stop

	end of file		end of tape

	OS I/O error		end of tape; if STOP_IOE, stop

By default, the magnetic tape is assigned to channel W.

2.13 Symbolic Display and Input

The SDS 940 simulator implements symbolic display and input.  Display is
controlled by command line switches:

	-a			display as ASCII character
	-c			display as four character SDS 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			four character SDS string
	alphabetic		instruction mnemonic
	numeric			octal number

Instruction input uses (more or less) standard SDS 940 assembler syntax.
There are eight instruction classes:

class		operands		examples	comments

no operand	none			EIR
POP (prog op)	op,addr{,tag}		POP 66,100
I/O		addr{,tag}		EOM 1266
mem reference	addr{,tag}		LDA 400,2
					STA* 300	indirect addr
reg change	op op op...		CLA CLB		opcodes OR
shift		cnt{,tag}		LSH 10
chan command	chan			ALC W		
chan test	chan			CAT Y

All numbers are octal.  Channel designators can be alphabetic (W, Y, C, D, E,
F, G, H) or numeric (0-7).  Tags must be 0-7, with 2 indicating indexing.