https://github.com/jblang/supermon64
Original sources and binaries for Supermon+64 V1.2 by Jim Butterfield
https://github.com/jblang/supermon64
6502 assembler assembly c64 commodore monitor retrocomputing
Last synced: 7 months ago
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Original sources and binaries for Supermon+64 V1.2 by Jim Butterfield
- Host: GitHub
- URL: https://github.com/jblang/supermon64
- Owner: jblang
- Created: 2017-01-05T03:45:50.000Z (about 9 years ago)
- Default Branch: master
- Last Pushed: 2024-01-31T21:48:38.000Z (about 2 years ago)
- Last Synced: 2025-06-23T01:07:57.215Z (8 months ago)
- Topics: 6502, assembler, assembly, c64, commodore, monitor, retrocomputing
- Language: Assembly
- Homepage:
- Size: 170 KB
- Stars: 143
- Watchers: 17
- Forks: 29
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# Supermon+64 V1.2
By Jim Butterfield et. al.
Supermon64 is a machine-language monitor for the Commodore 64. In modern parlance, it would be
called a debugger, providing functions including inspecting and altering registers and memory locations;
searching, comparing, and transferring blocks of memory; and assembling and disassembling machine code.
Here is a 10-minute video I made demonstrating many of its features: https://www.youtube.com/watch?v=MEjnMt_3wkU
## Contents
Original artifacts:
- [sprmon64.txt](sprmon64.txt) is a posting to comp.binaries.cbm
containing a uuencoded self-dissolving archive with the Supermon+64 V1.2
sources, instructions and binaries.
- [sprmon64.d64](sprmon64.d64) is a D64 image created from the
archive for use with VICE, disk drive emulators, or to create a real floppy disk.
- [supermon64.prg](supermon64.prg) is the original Supermon+64 binary taken from
the archive. The sources below will build an identical binary.
Modernized sources:
- [supermon64.asm](supermon64.asm) is the Supermon+64 V1.2 source code, converted to 64tass format
and heavily commented by me.
- [relocate.asm](relocate.asm) is the disassembled machine-code stub that loads Supermon+64 into
the top of BASIC memory.
- [build.py](build.py) is a python script I wrote that transforms the assembled relocator
stub and the fixed-location Supermon binaries into a relocatable binary.
- [Makefile](Makefile) is a GNU makefile that will build the final supermon64.prg binary
using the above sources.
## Background
Supermon is closely associated with [Jim Butterfield](https://en.wikipedia.org/wiki/Jim_Butterfield)
but it had many contributors over the years. The original version of Supermon for the Commodore PET
contained the following credits:
- Dissassembler by Wozniak/Baum
- Single step by Jim Russo
- Most other stuff (,HAFT) by Bill Seiler
- Tidied & Wrapped by Jim Butterfield
The earliest documented appearance of Supermon that I could find was in the
[January 1980 issue of The Transactor](https://archive.org/details/transactor-magazines-v2-i08).
From its origins on the PET, Supermon made its way to the VIC and the Commodore 64. It apparently
shares some DNA with the monitor and mini assembler on the Apple II as well as Micromon
and MADS monitors on various Commodore computers.
The first version for the Commodore 64 appeared as a type-in program in the
[January 1983 issue of Compute Magazine](https://archive.org/details/1983-01-compute-magazine).
An improved version followed in 1985, updated to include the features in the built-in monitors
for the Commodore Plus/4 and 128. This is the version that is preserved here.
Supermon 64 was widely distributed by Commodore User's Groups and included on the
[demo diskettes](http://www.zimmers.net/anonftp/pub/cbm/demodisks/c64/starter-kit.d64.gz)
and tapes that Commodore provided with their hardware. It was also included as a type-in
program in the back of many books on machine language programming, including Rae West's
[Programming the Commodore 64: The Definitive Guide](https://archive.org/download/Compute_s_Programming_the_Commodore_64_The_Definitive_Guide/Compute_s_Programming_the_Commodore_64_The_Definitive_Guide.pdf)
and Jim Butterfield's own
[Machine Language for the Commodore 64](https://archive.org/details/Machine_Language_for_the_Commodore_Revised_and_Expanded_Edition).
More than 30 years later, I decided to learn 6502 assembly. After working my way through
Jim Butterfield's excellent book using Supermon64, I wanted to find some real assembly code to
study, and the software I had just been using seemed like a natural place to start. I started
looking for the sources online but for a piece of public domain software, it wasn't as easy as
to find as you'd think.
I found [this thread](http://comp.sys.cbm.narkive.com/KUAL6oqM/attn-jim-butterfiled-i-m-looking-for-supermon-64-source-code)
on comp.sys.cbm where someone asked for the sources and Jim Butterfield himself responded, but
at the time he didn't have easy access to the sources. One person pointed to this
[modified version](http://www.ffd2.com/fridge/programs/supermon.s)
but I wanted the original. Someone else mentioned a file called SPRMON64.SDA at a now-defunct FTP
site. I googled for the filename and found what was apparently the last remaining copy on the internet
on a [gopher proxy](https://gopherproxy.meulie.net/sdf.org/1/users/rogertwo/prgs/cbm/c64/programming/).
I downloaded it and found that it contains what appear to be the original source and binaries
for the updated 1.2 version. Since it doesn't seem to have an official home and it's
continued availability on the internet seemed precarious, I decided to give it one on GitHub.
I modernized the source code so it can be built using the [64tass](https://sourceforge.net/projects/tass64/)
cross-assembler. The original source (included on the D64 image) was almost completely uncommented and used a
few constructs that were unsupported by 64tass. I converted these to the equivalent 64tass constructs,
indented the code, and then worked my way through the code line-by-line until I understood it all, commenting
it as I went along.
As Jim noted in his usenet posting, the provided sources don't produce the final Supermon 64 binary:
>I should note that, since Supermon+64 is relocatable code, the source
does not assemble into the final binary file. It may seem crude, but
I follow this procedure: (1) The source is carefully structured so
that there are no "dispersed addresses" such as might be created with
something like LDA #>VECTOR .. LDY #0200 4d 20 32 30 30 20 32 30: m 200 20
>0208 39 00 00 04 00 04 00 04: 9.......
```
Display memory from 0200 hex to 0209 hex. Display is in lines of
8, so addresses $200 to $20f are shown. If only one address is
used then 12 lines (96 locations) will be shown. If no address is
given display will go from the last address. Equivalent ASCII
characters are shown in reverse at the right. Values are changed
by typing over the display followed by a return character.
### Exit to BASIC
```
x
```
Return to BASIC READY mode. When you wish to return to SUPERMON+,
command "SYS 8".
### Simple Assembler
```
a 2000 lda #+18
```
changes to:
```
a 2000 a9 12 lda #$12
a 2002 ..next instruction
```
In the above example the user started assembly at 2000 hex. The
first instruction was load a register with immediate 18
decimal. In following lines the user need not type the "a" and
address. The simple assembler prompts with the next address. To
exit the assembler type a return after the the address prompt.
Previous lines may be changed by typing over the right hand part.
### Disassembler
```
d 2000 2004
. 2000 a9 12 lda #$12
. 2002 9d 00 80 sta $8000,x
```
Disassembles instructions from 2000 to 2004 hex. If one address
is given, 20 bytes will be disassembled. If no address,
start from the last used address.
Code may be reassembled by moving the cursor back and typing over
the right hand part.
### Fill Memory
```
f 1000 1100 ff
```
fills the memory from 1000 hex to 1100 hex with the byte ff hex.
### Go (run)
```
g 1000
```
Go to address 1000 hex and begin running code. If no address is
given, the address from the register is used.
### Jump (subroutine)
```
j 1000
```
Call address 1000 hex and begin running code. Return to the
monitor.
### Hunt Memory
```
h c000 d000 'read
```
Hunt thru memory from c000 hex to d000 hex for the ascii string
"read" and print the address where it is found. A maximum of
32 characters may be used.
```
h c000 d000 20 d2 ff
```
Hunt memory from c000 hex to d000 hex for the sequence of bytes
20 d2 ff and print the address. A maximum of 32 bytes may be used.
### File Handling
#### Load
```
l
```
Load any program from cassette #1.
```
l "ram test"
```
Load from cassette #1 the program named "ram test".
```
l "ram test",08
```
Load from disk (device 8) the program named "ram test". This
command leaves basic pointers unchanged.
#### Save
```
s "program name",01,0800,0c80
```
Save to cassette #1 memory from 0800 hex up to but not including
0c80 hex and name it "program name".
```
s "0:program name",08,1200,1f50
```
Save to disk drive #0 memory from 1200 hex up to but not including
1f50 hex and name it "program name".
### Transfer Memory
```
t 1000 1100 5000
```
Transfer memory in the range 1000 hex to 1100 hex and start storing
it at address 5000 hex.
### Compare Memory
```
c 1000 1100 5000
```
Compare memory in the range 1000 hex to 1100 hex with memory
starting at address 5000 hex.
### Disk Operations
```
@
```
Get disk status message
```
@9
```
Get disk unit 9 status message
```
@,$0
```
Get drive 0 directory
```
@,s0:temp
```
Scratch file 'temp' from disk
### Output to Printer
Call SUPERMON+ from basic with:
```
open 4,4:cmd 4:sys 8
```
All commands will go the printer. When complete, return to basic
with "x" and command:
```
print#4:close 4
```
### Summary
- `$ , + , & , %` number conversion
- `g` go (run)
- `j` jump (subroutine)
- `l` load from tape or disk
- `m` memory display
- `r` register display
- `s` save to tape or disk
- `x` exit to basic
- `a` simple assembler
- `d` disassembler
- `f` fill memory
- `h` hunt memory
- `t` transfer memory
- `c` compare memory
- `@` disk status/command
### Restarting Supermon
Supermon will load itself into the top of memory...wherever that happens to
be on your machine. Be sure to note the SYS command which links SUPERMON
to the Commodore. It may be used to reconnect the monitor if it is
accidentally disconnected by use of the run-stop/restore keys.
## License
To the best of my knowledge, this software is in the public domain. I claim no ownership.
The comments in `supermon64.asm` and `relocate.asm` as well as the entirety of `build.py` are my own.
I hereby place them in the public domain. However, I would greatly appreciate attribution if you make use of them.