Porting Code Between PIC chips (PS1 Modchip)

Hello.

At the moment I have about a dozen PIC12F683 chips looking for homes in some of my older PS1 consoles. The only MM3 hex for re-writable chips which I have on hand is written for the similar but slightly inferior PIC12F629 chips and I was wondering what would be necessary to port the code to something compatible with PIC12F683 (if it isn't compatible already).

It might be the case that someone has already made this code available, and I simply wasn't able to find it.

If anyone could advise future users in a similar predicament with where to find this code, or how to port it themselves, it would be much appreciated.

Here is a dump of the hex, for reference:

 

Might just work as is, only difference is the osc I think? So that might need a code tweak if it doesn't.

 

It will require a significant amount of rewriting to run on those later chips.

The most significant issue is that the old modchip code made heavy use of the TRIS instruction to set pins to tristate mode. By the time the 12F629 came out, this instruction was deprecated (along with OPTION) - but it still worked. On the later chips like the 12F683, it's actually been deleted.

Basically, you will have to go through the code and replace every instance of the TRIS instruction with
BSF STATUS,RP0
MOVWF GPIO
BCF STATUS,RP0

Obviously you need to keep an eye out for skips when doing this, too.

 

Alright, thanks for the tip. I'll get to it after I knock some repairs out of the way.

I'll do some more research and come back if I hit a roadblock.

This has been my quick reference:
http://www.pages.drexel.edu/~kws23/tutorials/PICTutorial/PICTutorial.html

 

Ah good tips. There's a post on psx-scene about someone who was porting it for old crow, but their code is still using tris, so not sure how that was supposed to work.

 

This is the reference I've been consulting so far: http://www.pages.drexel.edu/~kws23/tutorials/PICTutorial/PICTutorial.html

Thanks for the pointers. I made a post earlier, but it was lost in approval limbo. I'll continue to research and experiment, and I'll come back if I hit a roadblock.

 

The source for the 12f629 version of MM3 is available btw, I dont know why anyone would bother porting old crow.

https://dl.dropboxusercontent.com/u/28488139/Source.rar

 

Yep, I was only mentioning the old crow as a basis to see how that other guy was porting 12f629 code to 12f683. But it looks like he didn't get very far since there was still tris commands.

I have 683's that I would enjoy using for mm3, maybe I'll give it a shot at tweaking if possible. Good way to learn some assembly I suppose.