disassembling the MPS 1230 firmware

From: Marko Mäkelä (msmakela_at_cc.hut.fi)
Date: 2001-08-02 08:31:54

On Thu, 2 Aug 2001, laser wrote:

> I'm sorry to trouble you again, but I need some advise.  I'd like
> modify "commodore MPS 1230" firmware but I have not correct
> DISASSEMBLER for it.  So, my ask is:  where can I find a correct
> DISASSEMBLER for this firmware?

The firmware dump at http://www.funet.fi/pub/cbm/firmware/printers/1230/
is 64 kilobytes long.  The data between $a430 and $ffff is $ff.  I don't
think that the microcontroller in the MPS 1230 is 6502 compatible, since
the 6502 has its jump vectors (IRQ, NMI and RESET interrupt vectors) at
the top of the memory ($fffa-$ffff).

It could also be that this ROM contains only font data, and the actual
program code is inside the microcontroller chip.  One thing that you could
try is to convert the binary data to a monochrome bitmap format that can
be read in a drawing program.  Vary the width of the picture (in the
conversion program you have to write) until you can figure out how the
characters are laid out.

I was able to recognize some kind of a period in the data.  Starting from
$5000 hexadecimal, there are new blocks (separated with $ff blocks) at
multiples of 83*16 bytes (decimal), $530 hexadecimal.

I'm sending a copy of this message to the cbm-hackers mailing list, in
case someone there knows this printer (I don't).


       Message was sent through the cbm-hackers mailing list

Archive generated by hypermail 2.1.1.