simh-testsetgenerator/Interdata/id_doc.txt

To:	Users
From:	Bob Supnik
Subj:	Interdata 16b/32b Simulator Usage
Date:	15-Jan-2003

			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) 1993-2003, 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 Interdata 16b and 32b simulators.


1. Simulator Files

sim/		sim_defs.h
		sim_rev.h
		sim_sock.h
		sim_tmxr.h
		scp.c
		scp_tty.c
		sim_sock.c
		sim_tmxr.c

sim/interdata/	id_defs.h
		id16_cpu.c	[or id32_cpu.c]
		id16_dboot.c	[or id32_dboot.c]
		id_dp.c
		id_fd.c
		id_fp.c
		id_idc.c
		id_io.c
		id_lp.c
		id_mt.c
		id_pas.c
		id_pt.c
		id_tt.c
		id_ttp.c
		id_uvc.c
		id16_sys.c	[or id32_sys.c]

2. Interdata Features

The Interdata simulator includes simulators for a variety of 16b (I3, I4,
I5, 70, 80, 7/16, 8/16, 8/16E) and 32b (7/32, 8/32) models.  This is by
no means a complete sampling of all the variations in the Interdata/Perkin-
Elmer family.  The 32b family included options for special communications
instructions (7/32C, 8/32C), as well as a later extension for virtual
memory (3200 series).

The Interdata simulator is configured as follows:

device		simulates
name(s)

CPU - 16b	Interdata 3, 4, 5, 70, 80, 7/16, or 8/16 CPU with 64KB memory
		Interdata 8/16E CPU with 256KB memory
CPU - 32b	Interdata 7/32 or 8/32 CPU with 1MB memory
SELCH		selector channel (1-4)
PT		paper tape reader/punch
TT		console terminal, Teletype interface
TTP		console terminal, PASLA interface
LFC		line frequency clock
PIC		programmable interval clock
LPT		line printer
FD		floppy disk
DP		2.5MB/10MB cartridge disk
DM		mass storage module (MSM)/intelligent (IDC) disk controller
MT		magnetic tape
PAS		programmable asynchronous line controller
PASL		programmable asyhchronous lines, up to 32

The Interdata simulator implements two unique stop conditions:

	- decode of an undefined instruction, and STOP_INST is set
	- runaway carriage control tape in the line printer.

The LOAD command is used to load a carriage control tape for the line
printer.  The DUMP command is used to dump a contiguous portion of
memory as a self-loading bootstrap paper tape.  The syntax for the DUMP
command is:

	DUMP <filename> lowaddr-highaddr

The low address must be greater than or equal to X'D0'.

Devices are assigned their default device numbers, as documented in the
Interdata literature.  Device numbers can be changed by the command:

	SET <device> DEVNO=num

Device number conflicts are not checked until simulation starts.  If
there is a device number conflict, simulation stops immediately with
an error message.

Selector channel devices are assigned by default to selector channel 0.
Selector channel assignments can be changed by the command:

	SET <dev> SELCH=num

Selector channel assignments cannot introduce conflicts.

Most devices can be disabled and enabled, with the commands:

	SET <dev> DISABLED
	SET <dev> ENABLED

All devices are enabled by default.

2.1 CPU (16b)

The CPU options include memory size and CPU type:

	SET CPU I3		Interdata 3 (base instruction set)
	SET CPU I4		Interdata 4 (base plus single precision
				floating point)
	SET CPU 716		Interdata 7/16 (extended instruction set)
				(equivalent to Models 5, 70, and 80)
	SET CPU 816		Interdata 8/16 (extended plus double
				precision floating point)
	SET CPU 816E		Interdata 8/16E (extended plus double
				precision plus expanded memory)
	SET CPU 8K		set memory size = 8KB
	SET CPU 16K		set memory size = 16KB
	SET CPU 24K		set memory size = 24KB
	SET CPU 32K		set memory size = 32KB
	SET CPU 48K		set memory size = 48KB
	SET CPU 64K		set memory size = 64KB
	SET CPU 128K		set memory size = 128KB (8/16E only)
	SET CPU 256K		set memory size = 256KB (8/16E only)
	SET CPU CONSINT		assert console interrupt (7/16, 8/16,
				and 8/16E only)

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 64KB.

These switches are recognized when examining or depositing in CPU memory
(or any other byte oriented device):

	-b			examine/deposit bytes
	-w			examine/deposit halfwords (CPU default)
	-f			examine/deposit fullwords
	-d			data radix is decimal
	-o			data radix is octal
	-h			data radix is hexadecimal
	-v			interpret address as virtual

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

	name		size	comments

	PC		16	program counter
	R0..R15		16	general registers
	FR0..F14	32	single precision floating point registers
	D0H..D14H	32	double precision floating point registers,
				high order
	D0L..D14L	32	double precision floating point registers,
				low order
	PSW		16	processor status word
	CC		4	condition codes, PSW<12:15>
	SR		16	switch register
	DR		32	display register low 16 bits
	DRX		8	display register extension (x/16 only)
	DRMOD		1	display mode
	DRPOS		2	display pointer position
	SRPOS		1	switch pointer position
	IRQ[0:3]	32	interrupt requests
	IEN[0:3]	32	interrupt enables
	STOP_INST	1	stop on undefined instruction
	STOP_WAIT	1	stop if wait state and no I/O events pending
	PCQ[0:63]	16	PC prior to last branch or interrupt;
				most recent PC change first
	WRU		8	interrupt character

2.2 CPU (32b)

The CPU options include memory size and CPU type:

	SET CPU 732		Interdata 7/32, single precision floating point
	SET CPU DPFP		Interdata 7/32, double precision floating point
	SET CPU 832		Interdata 8/32 (double precision floating point)
	SET CPU 64K		set memory size = 64KB
	SET CPU 128K		set memory size = 128KB
	SET CPU 256K		set memory size = 256KB
	SET CPU 512K		set memory size = 512KB
	SET CPU 1M		set memory size = 1024KB
	SET CPU CONSINT		assert console interrupt

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 1024KB.

These switches are recognized when examining or depositing in CPU memory
(or any other byte oriented device):

	-b			examine/deposit bytes
	-w			examine/deposit halfwords
	-f			examine/deposit fullwords (CPU default)
	-d			data radix is decimal
	-o			data radix is octal
	-h			data radix is hexadecimal
	-v			interpret address as virtual

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

	name		size	comments

	PC		20	program counter
	R0..R15		32	active general register set
	GREG[32]	32	general register sets, 16 x 2
	FR0..FR14	32	single precision floating point registers
				if double precision floating point; for
				microcoded floating point, floating point
				registers are kept in memory locations 00 - 1F
	D0H..D14H	32	double precision floating point registers,
				high order
	D0L..D14L	32	double precision floating point registers,
				low order
	PSW		16	processor status word
	CC		4	condition codes, PSW<12:15>
	SR		16	switch register
	DR		32	display register low 16 bits
	DRX		8	display register extension (x/16 only)
	DRMOD		1	display mode
	DRPOS		2	display pointer position
	SRPOS		1	switch pointer position
	MACREG[0:15]	32	memory access controller segment registers
	MACSTA		5	memory access controller interrupt status
	IRQ[0:3]	32	interrupt requests
	IEN[0:3]	32	interrupt enables
	STOP_INST	1	stop on undefined instruction
	STOP_WAIT	1	stop if wait state and no I/O events pending
	PCQ[0:63]	20	PC prior to last branch or interrupt;
				most recent PC change first
	WRU		8	interrupt character

2.3 Selector Channel (SELCH)

An Interdata system can have 1 to 4 selector channels (SELCH0, SELCH1,
SELCH2, SELCH3).  The default number of channels is 2.  The number of
channels can be changed with the command:

	SET SELCH CHANNELS=num

The selector channels implement these registers:

	name		size	comments

	SA[0:3]		20	start address, channels 0 to 3
	EA[0:3]		20	end address, channels 0 to 3
	CMD[0:3]	8	command, channels 0 to 3
	DEV[0:3]	8	active device, channels 0 to 3
	RDP[0:3]	2	read byte pointer, channels 0 to 3
	WDC[0:3]	3	write data counter, channels 0 to 3
	IREQ		4	interrupt requests; right to left,
				channels 0 to 3
	IENB		4	interrupt enables

2.4 Programmed I/O Devices

2.4.1 Paper Tape Reader/Punch (PT)

The paper tape reader and punch (PT units 0 and 1) read data from or
write data to disk files.  The RPOS and PPOS registers specify the
number of the next data item to be read and written, respectively.
Thus, by changing RPOS or PPOS, the user can backspace or advance
these devices.

The paper tape reader supports the BOOT command.  BOOT PTR copies the
so-called '50 loader' into memory and starts it running.

The paper tape controller implements these registers:

	name		size	comments

	RBUF		8	reader buffer
	RPOS		32	reader position in the input file
	RTIME		24	time from reader start to interrupt
	RSTOP_IOE	1	reader stop on I/O error
	PBUF		8	punch buffer
	PPOS		32	punch position in the output file
	PTIME		24	time from punch start to interrupt
	PSTOP_IOE	1	punch stop on I/O error
	IREQ		1	paper tape interrupt request
	IENB		1	paper tape interrupt enable
	IARM		1	paper tape interrupt armed
	RD		1	paper tape read/write mode
	RUN		1	paper tape running
	SLEW		1	paper tape reader slew mode
	EOF		1	paper tape reader end of file

Error handling is as follows:

	type	error	     STOP_IOE	processed as

	in,out	not attached	1	report error and stop
				0	out of tape

	in	end of file	1	report error and stop
				0	out of tape

	in,out	OS I/O error	x	report error and stop

2.4.2 Console, Teletype Interface (TT)

The Teletype keyboard (TT0) reads from the console keyboard; the
Teletype printer (TT1) writes to the simulator console window.
The Teletype units (TT0, TT1) 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 unit changes both.  The default mode is KSR.

The Teletype has a BREAK key, which is not present on today's
keyboards.  To simulate pressing the break key, stop the simulator
and use the command:

	SET TT BREAK

Break status will be asserted, and will remain asserted for the
interval specified by KTIME.

The Teletype interface implements these registers:

	name		size	comments

	KBUF		8	input buffer
	KPOS		32	number of characters input
	KTIME		24	input polling interval
	TBUF		8	output buffer
	TPOS		32	number of characters output
	TTIME		24	time from output start to interrupt
	IREQ		1	interrupt request
	IENB		1	interrupt enable
	IARM		1	interrupt armed
	RD		1	read/write mode
	FDPX		1	half-duplex
	CHP		1	input character pending

2.4.3 Console, PASLA Interface (TTP)

Later Interdata system connect the system console via the first
PASLA interface rather than the Teletype interface.  The PASLA
console can be simulated with a Telnet session on the first PAS line.
Alternately, the PASLA console can be attached to the simulator
console window, using the TTP device in place of TT.

To switch the simulator console window to TTP, use the command:

	SET TTP ENABLED or
	SET TT DISABLED

Device TT is automatically disabled and device TTP is enabled.
To switch the simulator console window back to TT, use the command:

	SET TT ENABLED or
	SET TTP DISABLED

Device TTP is automatically disabled and device TT is enabled.
If TTP is enabled at its default device settings, the base address
for the PAS multiplexor must be changed:

	SET PAS DEVNO=12

Otherwise, a device number conflict occurs.

The PASLA keyboard (TTP0) reads from the console keyboard; the
PALSA printer (TTP1) writes to the simulator console window.
The PASLA units (TTP0, TTP1) can be set to one of three modes:
UC, 7B, or 8B.  In UC mode, lower case input and output characters
are automatically converted to upper case.  In 7B mode, input and
output characters are masked to 7 bits.  In 8B mode, characters
are not modified.  Changing the mode of either unit changes both.
The default mode is UC.

To simulate pressing the break key, stop the simulator and use
the command:

	SET TTP BREAK

Break status will be asserted, and will remain asserted for the
interval specified by KTIME.

The PASLA console interface implements these registers:

	name		size	comments

	KBUF		8	input buffer
	KPOS		32	number of characters input
	KTIME		24	input polling interval
	KIREQ		1	input interrupt request
	KIENB		1	input interrupt enabled
	KARM		1	input interrupt armed
	CHP		1	input character pending
	TBUF		8	output buffer
	TPOS		32	number of characters output
	TTIME		24	time from output start to interrupt
	TIREQ		1	output interrupt request
	TIENB		1	output interrupt enable
	TIARM		1	output interrupt armed

2.4.4 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.

In addition, the line printer can be programmed with a carriage control
tape.  The LOAD command loads a new carriage control tape:

	LOAD <file>			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 0 and 7; column seven is by convention top of form.  The
following are all legal carriage control specifications:

	<blank line>			no punch
	(5)				5 lines with no punches
	1,5,7				columns 1, 5, 7 punched
	(10)2				10 lines with column 2 punched
	0				column 0 punched

The default form is 1 line long, with all columns punched.

The line printer implements these registers:

	name		size	comments

	BUF		7	last data item processed
	BPTR		8	line buffer pointer
	LBUF[0:131]	7	line buffer
	VFUP		8	vertical forms unit pointer
	VFUL		8	vertical forms unit length
	VFUT[0:131]	8	vertical forms unit table
	IREQ		1	line printer interrupt request
	IENB		1	line printer interrupt enable
	IARM		1	line printer interrupt armed
	POS		32	position in the output file
	CTIME		24	character processing time
	STIME		24	spacing operation 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

2.4.5 Line Frequency Clock (LFC)

The line frequency clock (LFC) implements these registers:

	name		size	comments

	IREQ		1	clock interrupt request
	IENB		1	clock interrupt enable
	IARM		1	clock interrupt armed
	TIME		24	clock frequency
	TPS		8	ticks per second (120 or 100)

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

2.4.6 Programmable Interval Clock (PIC)

The programmable interval clock (PIC) implements these registers:

	name		size	comments

	BUF		16	output buffer
	RIC		16	reset interval and rate
	CIC		12	current interval
	DECR		10	current decrement value
	RDP		1	read byte select
	OVF		1	interval overflow flag
	IREQ		1	clock interrupt request	
	IENB		1	clock interrupt enable
	IARM		1	clock interrupt armed

If the interval requested is longer than 1 msec, the programmable clock
auto-calibrates; if not, it simply counts instructions.

2.4.7 Floppy Disk Controller (FD)

Floppy disk options include the ability to make units write enabled or
write locked.

	SET FDn LOCKED		set unit n write locked
	SET FDn WRITEENABLED	set unit n write enabled

Units can also be set ONLINE or OFFLINE.

The floppy disk supports the BOOT command.  BOOT FDn copies an autoload
sequence into memory and starts it running.

The floppy disk controller implements these registers:

	name		size	comments

	CMD		8	command
	STA		8	status
	BUF		8	buffer
	LRN		16	logical record number
	ESTA[0:5]	8	extended status bytes
	DBUF[0:127]	8	transfer buffer
	DBPTR		8	transfer buffer pointer
	IREQ		1	interrupt request
	IENB		1	interrupt enabled
	IARM		1	interrupt armed
	CTIME		24	command response time
	STIME		24	seek time, per cylinder
	XTIME		24	transfer time, per byte
	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

Floppy disk data is buffered in memory; therefore, end of file and OS
I/O errors cannot occur.

2.4.8 Programmable Asynchronous Line Adapters (PAS, PASL)

The Programmable Asynchronous Line Adapters (PAS and PASL) represent,
indistinguishably, individual PASLA interfaces, two lines asynchronous
multiplexors, and 8 line asynchronous multiplexors, with a maximum
of 32 lines.  All the lines are modelled as a terminal multiplexor, with
PAS as the multiplexor controller, and PASL as the indivdual lines. The
PASLAs perform input and output through Telnet sessions connected to a
user-specified port.  The ATTACH command specifies the port to be used:

	ATTACH PAS <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 PASL) 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.  Each line (each unit of PASL) can also be set for modem
control with the command SET PASLn DATASET.  The defaults are UC mode
and DATASET disabled.

Once PAS 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 PAS DISCONNECT command,
or a DETACH PAS command.

The SHOW PAS CONNECTIONS command displays the current connections to the
extra terminals.  The SHOW PAS STATISTICS command displays statistics for
active connections.  The SET PAS DISCONNECT=linenumber disconnects the
specified line.

The controller (PAS) implements these registers:

	name		size	comments

	STA[0:31]	8	status, lines 0 to 31
	CMD[0:31]	16	command, lines 0 to 31
	RBUF[0:31]	8	receive buffer, lines 0 to 31
	XBUF[0:31]	8	transmit buffer, lines 0 to 31
	RIREQ		32	receive interrupt requests;
				right to left, lines 0 to 31
	RIENB		32	receive interrupt enables
	RARM[0:31]	1	receive interrupt armed
	XIREQ		32	transmit interrupt requests;
				right to left, lines 0 to 31
	XIENB		32	transmit interrupt enables
	XARM[0:31]	1	transmit interrupt armed
	RCHP[0:31]	1	receiver character present, lines 0 to 31

The lines (PASL) implements these registers:

	name		size	comments

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

The additional terminals do not support save and restore.  All open
connections are lost when the simulator shuts down or PAS is detached.

2.5 Cartridge Disk Controller (DP)

Cartridge disk options include the ability to make units write enabled or
write locked, and to select the type of drive:

	SET DPn LOCKED		set unit n write locked
	SET DPn WRITEENABLED	set unit n write enabled
	SET DPn 2315		set unit n to 2315 (2.5MB)
	SET DPn 5440		set unit n to 5440 (10MB)

Units can also be set ONLINE or OFFLINE.

The cartridge disk supports the BOOT command.  To boot OS16/32, the hex
form of the operating system file's extension must be placed in locations
7E:7F.  The disk bootstrap looks for a valid OS16/32 volume descriptor in
block 0, and uses that to locate the volume directory.  It then searches
the directory for a filename of the form OS16xxxx.hhh or OS32xxxx.hhh,
where the xxxx is ignored and hhh is the ASCII form of the extension from
locations 7E:7F.  The 32b bootstrap can also boot Wollongong UNIX; locations
7E:7F must be 0.

All drives have 256 8b bytes per sector.  The other disk parameters are:

	drive cylinders surfaces sectors

	2315	203	  2	   24
	5440	408	  4	   12

The cartridge disk controller implements these registers:

	name		size	comments

	CMD		3	current command
	STA		8	controller status
	BUF		8	controller buffer
	HDSC		8	current head/sector select
	CYL		8	current cylinder select
	DBUF[0:255]	8	transfer buffer
	DBPTR		16	transfer buffer point
	DBLNT		16	transfer buffer length
	FIRST		1	first DMA service flag
	IREQ		5	interrupt requests; right-to-left,
				controller, drives 0 to 3
	IENB		5	interrupt enables
	IARM[0:3]	1	interrupts armed, drives 0 to 3
	STIME		24	seek latency, per cylinder
	RTIME		24	rotational latency, per sector
	WTIME		24	inter-word latency

Error handling is as follows:

	error			processed as

	not attached		disk not ready

	end of file		assume rest of disk is zero

	OS I/O error		report error and stop

2.6 Mass Storage Module/Intelligent Disk Controller (DM)

MSM/IDC disk controller options include the ability to make units
write enabled or write locked, and to select the type of drive:

	SET DMn LOCKED		set unit n write locked
	SET DMn WRITEENABLED	set unit n write enabled
	SET DMn MSM80		set unit n to storage module, 80MB
				(67MB formatted)
	SET DMn MSM300		set unit n to storage module, 300MB
				(262MB formatted)
	SET DMn MCCD16		set unit n to medium capacity, 16MB
				(13.5MB formatted)
	SET DMn MCCD48		set unit n to medium capacity, 48MB
				(40.5MB formatted)
	SET DMn MCCD80		set unit n to medium capacity, 80MB
				(67MB formatted)
	SET DMn MSM330F		set unit n to storage module, 330MB
				(300MB formatted)

Note that the disk bootstraps can ONLY boot the MSM80 and MSM300.
Units can be set ONLINE or OFFLINE.

The MSM/IDC controller supports the BOOT command.  To boot OS16/32, the hex
form of the operating system file's extension must be placed in locations
7E:7F.  The disk bootstrap looks for a valid OS16/32 volume descriptor in
block 0, and uses that to locate the volume directory.  It then searches
the directory for a filename of the form OS16xxxx.hhh or OS32xxxx.hhh,
where the xxxx is ignored and hhh is the ASCII form of the extension from
locations 7E:7F.  The 32b bootstrap can also boot Wollongong UNIX; locations
7E:7F must be 0.  Note that only the MSM80 and MSM300 drives can be boot-
strapped; the boot code does not recognize the other drives.

All drives have 256 8b bytes per sector.  The other disk parameters are:

	drive cylinders surfaces sectors

	MSM80	 823	  5	   64
	MSM300	 823	 19	   64
	MCCD16	 823	  1	   64
	MCCD48	 823	  3	   64
	MCCD80	 823	  5	   64
	MSM300F	1024	 16	   64

The MSM/IDC disk controller implements these registers:

	name		size	comments

	STA		8	controller status
	BUF		8	controller buffer
	SEC		8	current sector select
	DBUF[0:767]	8	transfer buffer
	DBPTR		16	transfer buffer point
	DBLNT		16	transfer buffer length
	FIRST		1	first DMA service flag
	IREQ		5	interrupt requests; right-to-left,
				controller, drives 0 to 3
	IENB		5	interrupt enables
	SIREQ		5	saved interrupt requests
	ICARM		1	controller interrupt armed
	IDARM[0:3]	1	drive interrupts armed, drives 0 to 3
	STIME		24	seek latency, per cylinder
	RTIME		24	rotational latency, per sector
	WTIME		24	inter-word latency

Error handling is as follows:

	error			processed as

	not attached		disk not ready

	end of file		assume rest of disk is zero

	OS I/O error		report error and stop

2.7 Magnetic Tape Controller (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 ONLINE or OFFLINE.

The magnetic tape supports the BOOT command.  BOOT MTn copies an autoload
sequence into memory and starts it running.

The magnetic tape controller implements these registers:

	name		size	comments

	CMD		8	command
	STA		8	status
	BUF		8	buffer
	DBUF[0:65535]	8	transfer buffer
	DBPTR		16	transfer buffer pointer
	DBLNT		16	transfer buffer length
	XFR		1	transfer in progress flag
	FIRST		1	first DMA service flag
	IREQ		4	interrupt requests; right to left,
				drives 0 to 3
	IENB		4	interrupt enables
	IARM[0:3]	1	interrupts armed, drives 0 to 3
	STOP_IOE	1	stop on I/O error
	WTIME		1	word transfer time
	RTIME		1	interrecord latency
	UST[0:3]	8	unit status, drives 0 to 3
	POS[0:3]	32	tape position, drives 0 to 3

Error handling is as follows:

	error			processed as

	not attached		tape not ready; if STOP_IOE, stop

	end of file		set error flag

	OS I/O error		set error flag; if STOP_IOE, stop

2.8 Symbolic Display and Input

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

	-a			display as ASCII character
	-c			display as two 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
	alphabetic		instruction mnemonic
	numeric			octal number

2.7.1 16b Instruction Input

Instruction input uses standard Interdata assembler syntax.  There are
seven instruction classes: short branch, extended short branch, short
immediate, register, register-register, memory, and register-memory.

Short branch instructions have the format

	sbop mask,address

where the mask is a hex (decimal) number between 0 and F (15), and
the address is within +32 (forward branch) or -32 (backward branch)
of the current location.

Extended short branch instructions have the format

	sbxop address

where the address is within +32 or -32 of the current location.  For
extended short branches, the simulator chooses the forward or backward
direction automatically.

Short immediate instructions have the format

	siop regnum,immed

where the register number is a hex (decimal) number, optionally
preceded by R, between 0 and F (15), and the immediate is a hex digit
between 0 and F.

Register instructions have the format

	rop regnum

where the register number is a hex (decimal) number, optionally
preceded by R, between 0 and F (15).

Register-register instructions have the format

	rrop regnum,regnum

where the register numbers are hex (decimal) numbers, optionally
preceded by R, between 0 and F (15).

Memory instructions have the format

	mop address{(index)}

where address is a hex number between 0 and 0xFFFF, and the index
register is a hex (decimal) number, optionally preceded by R,
between 1 and F (15).

Register-memory instructions have the format

	rmop regnum,address{(index)}

where the register number is a hex (decimal) number, optionally
preceded by R, between 0 and F (15), the address is a hex number
between 0 and 0xFFFF, and the index register is a hex (decimal)
number, optionally preceded by R, between 1 and F (15).

2.7.2 32b Instruction Input

Instruction input uses standard Interdata assembler syntax.  There are
nine instruction classes: short branch, extended short branch, short
immediate, 16b immediate, 32b immediate, register, register-register,
memory, and register-memory.

Short branch instructions have the format

	sbop mask,address

where the mask is a hex (decimal) number between 0 and F (15), and
the address is within +32 (forward branch) or -32 (backward branch)
of the current location.

Extended short branch instructions have the format

	sbxop address

where the address is within +32 or -32 of the current location.  For
extended short branches, the simulator chooses the forward or backward
direction automatically.

Short immediate instructions have the format

	siop regnum,immed

where the register number is a hex (decimal) number, optionally
preceded by R, between 0 and F (15), and the immediate is a hex digit
between 0 and F.

16b immediate instructins have the format

	i16op regnum,immed16{(index)}

where the register number is a hex (decimal) number, optionally
preceded by R, between 0 and F (15), the immediate is a hex number
between 0 and 0xFFFF, and the index register is a hex (decimal)
number, optionally preceded by R, between 1 and F (15).

32b immediate instructions have the format

	i32op regnum,immed32{(index)}

where the register number is a hex (decimal) number, optionally
preceded by R, between 0 and F (15), the immediate is a hex number
between 0 and 0xFFFFFFFF, and the index register is a hex (decimal)
number, optionally preceded by R, between 1 and F (15).

Register instructions have the format

	rop regnum

where the register number is a hex (decimal) number, optionally
preceded by R, between 0 and F (15).

Register-register instructions have the format

	rrop regnum,regnum

where the register numbers are hex (decimal) numbers, optionally
preceded by R, between 0 and F (15).

Memory instructions have the format

	mop address{(index)} or
	mop address{(index1,index2)}

where address is a hex number between 0 and 0xFFFF, and the index
registers are hex (decimal) numbers, optionally preceded by R,
between 1 and F (15).

Register-memory instructions have the format

	rmop regnum,address{(index)} or
	rmop regnum,address{(index1,index2)}

where the register number is a hex (decimal) number, optionally
preceded by R, between 0 and F (15), the address is a hex number
between 0 and 0xFFFF, and the index registers are hex (decimal)
numbers, optionally preceded by R, between 1 and F (15).

For memory operands, the simulator automatically chooses the format
(RX1, RX2, RX3) that consumes the fewest bytes.  If both RX1 and RX2
are feasible, the simulator chooses RX1.