dp111 / picotube Goto Github PK

Hi,
as you're aware, I am currently working on a VIC-20 emulator for the Raspberry Pi Pico. However, I am having a hard time modifying the assembly code to get it to call an external C function. Specifically, I am having trouble doing anything in the LOAD_BYTE macro. Event if I just add the following :

   push {r0-r3}
   pop {r0-r3}

before the ldrb \rdst,[ rmem, \rsrc] line, the Pico crashes immediately (in my ignorance, I have adjusted the tablend label to tablend: . = 256*(I_ALIGN+1) to get it to fit. Could that be what's causing the issue ? )

Basically what I would like to achieve would be to replace ldrb \rdst,[ rmem, \rsrc] with a call to a C function that gets passed the address and returns the data.

Any guidance to help me along while I'm familiarizing myself with ARM assembly would be great.

Thanks!