Modify ColecoVision BIOS - Z80 Assembly Programming

[Jorisclayton]

Hello everyone, Im trying to modify the ColecoVision BIOS to adapt it for a homemade z80 computer that I build. Actually only the controllers interfaces are different from the colecovision ones, while colecovision needs complex routines to read the data from the keypad and the buttons of each controller, my own have a shift register addressed at ports E0 (Player 1) and E1 (Player 2), I need to modify it to simply read the data from this ports and interprate it as the pressed buttos for the games run. Im trying to understand a disassambled ColecoVision BIOS with Z80DASM and have in hands a commented version of a simmilar Coleco BIOS (but this one do not work when compyled, I do not know why, Im using it just to read the comments and try to match it with the disassembled version). The fact is that Im noob on assembly, I can understand the instructions and know a little how it works, already write simple programs like interfacing a PS/2 keyboard and a 16x2 LCD but Im having difficult to modify a BIOS with much entry points, jumps, subroutines and no labels. I already find the controller interface part and add some macros but Im far from understand it to the point to modify to my necessity. Does anyone there already make something like that and could help me with this specific problem?

I will anex here the BIOS files that im working, the H2Z80 one is the file that im trying to modify.
There is also the schematic for my computer if anyone wants to see it for understand more about my problem.

                  Here is how the controller interface looks like:

coleco_bios.asm coleco_bios_list.asm H2Z80_coleco_bios.asm H2Z80 Schematic 13MAIO2024.pdf