1227747 ROM image?

**shimniok** · 05-07-2013

Where might a fellow dig up an already-dumped ROM image (not EPROM, ROM) from a 1227747?

I'd like to, for my own curiosity, disassemble the ROM + EPROM code to get a better sense of how the code works.

I know that the ROM can be dumped, and I can do that, but why reinvent the wheel if someone already has a binary image of the ROM handy.

thanks!
Michael

**EagleMark** · 05-07-2013

I've never seen one. But I sure would like to know what's there? Especially the last hex of EPROM that directs to $00 or $96. Some chips have either, but what really peaked my interest was a 7.4L bin file that was superceeded 3 times, and the third one changed from $00 to $96

**jim_in_dorris** · 05-07-2013

42 hack.pdf contains both pieces. here it is

**jim_in_dorris** · 05-07-2013

I am not sure if I have seen the binary of the second half of the $42 binary anywhere. If someone has a dead 7747, we could unsolder the second rom and read it.

**shimniok** · 05-07-2013

Thanks guys. I didn't want to pollute the other thread with this question. :) Supposedly one can pull the image without desoldering using some pins exposed somewhere. Unfortunately the website that used to spell it out is lost to time. There's another site that has binaries that you can load into the EPROM and it'll spit out the data via serial.

**RobertISaar** · 05-07-2013

There's another site that has binaries that you can load into the EPROM and it'll spit out the data via serial.

i seem to remember reading about this on either the DIY-EFI site in the GM_ECM section or possibly directly from Ludis, i forget which at this point. in any case, that's the easiest route to go, though i seem to remember that the pins used for the serial communications were the IAC drivers, instead of the normal ALDL circuit?

**shimniok** · 05-07-2013

Here's the site I found: http://www.exatorq.com/ludis_obd1/spit.html

It has various EPROM images for dumping the ROM. You're right; it doesn't use the standard ALDL pin.

Ground ECM pins A12 & D1. Connect a 12 volt power source to ECM pins A6, B1 & C16. Connect the positive end of a 1 µF capacitor to ECM pin C6. Note, this is not the regular ALDL output pin. Connect the negative end of the capacitor to your computer's RxD serial port input. (Also provide a ground connection between the ECM and serial port.) On the computer, run a terminal emulator set to 8-N-2 and 9600 baud. The ROM contents should now be dumped repeatedly to your terminal in Motorola S19 format.