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1992-05-06
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SimCPM - a CP/M simulator for the Amiga
by Jim Cathey and Charlie Gibbs
incorporating modifications by Willi Kusche
Version 2.3 - January 9, 1989
This is a FREELY-DISTRIBUTABLE program. Spread it around all
you like, just don't sell it, and please keep the entire package
(including this file) intact. If you find any bugs or make any
changes, please let me know - I'd like to keep my copy up to date.
This program is based on an article by Jim Cathey which ran in
Dr. Dobb's Journal from January to March 1986. The original program
emulated an 8080, including CP/M BIOS and BDOS calls, on a CP/M-68K
system. I have modified the operating system interface to run under
AmigaDOS (from the CLI only, which shouldn't bother most CP/M-ers :-).
Willi Kusche maintains that the proper term is "emulator", rather
than "simulator." Although I agree, the original article called it a
simulator, and the name seems to have stuck.
*** NEW FOR VERSION 2.0 *** Due to popular demand, I have added
support for the entire Z-80 instruction set (including undocumented
opcodes).
WARNING! This program uses the MOVE from SR instruction to set up
the simulated Z-80 flags. Therefore, it will not run on the 68010 or
higher processors. I didn't want to use the Exec's GetCC() call because
it would be too slow. As a work-around I have set up a EQUate in
options.i which you can change to indicate that you are running on a
68010, 68020, etc. Re-assembling with x680x0 equated to 1 will cause
all MOVE from SR instructions to be replaced by the corresponding MOVE
from CCR instructions (actually faked with a DC.W in case your assembler
doesn't support 68010 opcodes). I have assembled a version with this
flag set, and included it in the package; it is named SimCPM010.
It should be possible to check whether x680x0 is equated to 2 and
generate code optimized for a 68020 (as if it wouldn't be fast enough
as is :-).
SimCPM only looks at the first 12 bytes of the FCB (drive code,
file name, and file type) when opening a file. The remainder of the
FCB is neither altered nor checked, except for BDOS calls 17 (search
for first file) and 18 (search for next file), which insert extent size
and count information only.
If a reference is made to any drive other than A:, SimCPM will
insert the string CPMx: ahead of any file name it uses. For instance,
if a program tries to open MYFILE.DAT on drive B:, SimCPM will try to
open CPMB:MYFILE.DAT. You can ASSIGN these simulated drives anywhere
you want. Drive A: will always go to the current directory, unless the
user number is not zero. If you specify any user number other than
zero, it will be included, e.g. if the above example were opened under
user 1, SimCPM will look for CPMB01:MYFILE.DAT. If the file were on
drive A under user 1, SimCPM will look for CPMA01:MYFILE.DAT.
The only built-in commands supported are USER and SAVE. All
others, such as DIR or TYPE, can easily be done using AmigaDOS
equivalents. You might want to RUN SimCPM so that the original
CLI window will be available for this.
The EI and DI instructions are currently ignored.
The IN and OUT instructions are ignored except for ports 14 and
15. Access to the Amiga's serial port is provided through a simulated
Intel 8251 USART, which is currently set up to run at 1200 bps. Data
is read from or written to port 14, and status input is simulated on
port 15. All output to port 15 (command) is ignored. Note that CPU
overhead may not permit an effective throughput of 1200 bps. (Yup,
you guessed it, it emulates the modem port on my old IMSAI.)
The following BDOS calls are not supported:
3 - reader input
4 - punch output
30 - set file attributes
all above 36
The only BIOS calls supported are those for program termination
and console and list I/O. (Low-level disk access could get scary.)
If a program attempts to use an unsupported BIOS or BDOS call, an
appropriate error message will be displayed, along with a register dump,
and the program will be terminated.
Basic H19 terminal emulation (similar to a VT52) has been
provided. Escape sequences for cursor positioning, cursor to home,
screen clearing, and insert and delete modes are translated to the
corresponding Amiga sequences. The program MANDOG.COM, which I
wrote for my original CP/M (H19) system and copied here unchanged,
demonstrates the cursor addressing capabilities of SimCPM. Any escape
sequences that SimCPM can't recognize are passed through unchanged.
You can disable all escape sequence translation by changing the equated
value "h19" (in options.i) to from 1 to 0 and re-assembling.
To speed up console output for programs which write one character
at a time, I have included a buffered output option. If you include
the -b switch on the command-line parameter, all console output will be
held until one of the following events occurs:
- a carriage return, line feed, or bell character is written
- the buffer (currently 2K) becomes full
- a BIOS or BDOS call other than console output is made.
It should be possible to use buffered output in just about any program.
Note that if a program uses the "console output string" function (BDOS
call 9), the entire string is written in a single operation even when
buffering is not requested.
If you include the -t switch on the command line, instruction
and/or BIOS/BDOS tracing is available. Simulations run somewhat slower
with this flag set, even if tracing is not currently active. Tracing
is done using 8080 mnemonics by default. If you want Z-80 mnemonics,
use -z instead of -t. If both -z and -t are specified, -t will be
ignored.
If the trace switch has been specified, SimCPM will prompt you
for starting and ending addresses for tracing, and whether you want
BIOS/BDOS calls traced. Simulation starts with tracing disabled. When
SimCPM executes an instruction at the starting address, tracing is
turned on. All Z-80 registers and the top four stack entries, as well
as the current instruction, are displayed for each instruction until
the ending address is reached. Tracing is then disabled until the
start address is again encountered. After displaying 8 instructions,
execution is suspended; enter S to stop tracing and continue executing,
Q to quit the program, C to change the starting and ending addresses
for tracing, or any other key to trace the next 8 instructions.
If you have requested BIOS/BDOS call tracing, the message
BIOS CALL nn (hex) AT aaaa
or
BDOS CALL nn (hex) AT aaaa
will be displayed each time a BIOS or BDOS call is made. The BDOS
call number (contents of register C in hex) will replace "nn" for BDOS
calls, while BIOS calls will set "nn" to a sequential number starting
at 01 for program termination, 02 for console status, etc. The address
where the call is made will be taken from the top of the stack and
displayed in place of "aaaa".
List output is sent to PRT:RAW. This ensures that no newline
translation will take place. The printer is not opened until the first
attempt is made to access it. If the printer cannot be opened for any
reason, the program will be terminated. At program termination the
printer will be closed if it was used.
If SimCPM is brought up with no command-line parameters, it will
present the standard CP/M A> prompt. At this point you can run CP/M
.COM files just like on a normal CP/M system. The command line will
be scanned for up to two FCBs and the tail will be passed to the
program. When the program terminates, the A> prompt will be
re-displayed. To return to AmigaDOS, enter a control-C (CP/M warm
boot) at the A> prompt.
If command-line parameters are given, they will be passed to
SimCPM as if they had been entered at the A> prompt. When the program
terminates, SimCPM will automatically return to AmigaDOS. This allows
you to run CP/M programs from an EXECUTE file.
Here are some sample invocations of SimCPM:
simcpm
Loads the simulator, which presents the A> prompt and
waits for CP/M commands. Type control-C at the prompt
to exit.
simcpm -b
Same as above, except console output buffering is used.
simcpm myprog
Loads the simulator, which loads and runs the CP/M
program MYPROG.COM. When MYPROG terminates, SimCPM
returns to AmigaDOS.
simcpm -t myprog
Same as above, except that before MYPROG.COM is run,
you will be prompted for trace parameters.
simcpm -z myprog
Same as above, except that Z-80 mnemonics will be used
for tracing, rather than 8080 mnemonics.
simcpm mbasic basprog
Loads the simulator, which loads Microsoft BASIC-80 (if
you have it), which in turn loads and runs BASPROG.BAS.
When BASPROG issues a SYSTEM command, SimCPM returns
to AmigaDOS.
simcpm -b mbasic basprog
Same as above, but with console output buffering. Since
MBASIC does all console I/O one character at a time, the
buffered option can speed it up considerably.
I have included two CP/M programs for demonstration purposes.
TESTPROG.COM is a simple "hello, world" program (try it using the
trace option), while MANDOG.COM demonstrates cursor addressing for
an emulated H19 terminal.
SimCPM consists of two source modules, SIMCPM1.ASM and
SIMCPM2.ASM. No include files are needed, although amiga.lib is
required for linking. The makefile is set up to use my own assembler,
A68k, and BLink - it should be relatively easy to adapt it to whatever
assembler and linker you are using.
Special thanks to:
Jim Cathey for his article in Dr. Dobb's Journal -
it provided the starting point for this program.
Willi Kusche (for new ideas and corrections of my Z-80 code)
SYSOP
KMMM Pascal BBS
(609) 232-0773
24 hours a day
7 days a week
300/1200/2400/9600 bps
9600 is USRobotics HST protocol
Passing a simple IQ test required for full access
Please address any kudos, flames, etc. to
Charlie Gibbs
2121 Rindall Avenue
Port Coquitlam, B.C.
Canada
V3C 1T9
or to Larry Phillips or Jeff Lydiatt on CompuServe or Usenet.
(I don't have the time or money to live there myself.)