how to get source code for an original Colecovision game

[Swami]

Can anyone tell me how get the source code for an original Colecovision game, like Centipede?

[Nukey Shay]

Does any still exist of commercial Colecovision games?  It's pretty rare when source is found (regardless of platform).

 

BTW, source code is the actual program assembly files/modules/etc created by the original developer.  Most often, these files are lost forever when a company ceases development...reappearing only when some backup copy or printout was forgotten about in some programmer's attic.

 

A disassembly is an attempted reconstruction of an assembly file, created by examining a programs' binary cartridge or disk data...and translating those bytes back into assembly mnemonic instructions, arguments, and data tables.

 

Reverse-engineering takes the disassembly process one step further, replacing generic labels with descriptive names and adding comments explaining what the program lines are doing.  Depending on the complexity of the program, this process could take a very long time for even an accomplished programmer to decipher.  And even then, the original programmers' comments and label names are unrecoverable.

 

By contrast, a beginning disassembly file can be generated automatically using a program disassembler...requiring only minimal human assistance (to correctly separate program code from data tables).  I never attempted Colecovision disassembly, but dZ80 is supposed to have a good rep.

http://www.inkland.org.uk/dz80/

[Swami]

23 hours ago, Nukey Shay said:

Does any still exist of commercial Colecovision games?  It's pretty rare when source is found (regardless of platform).

 

BTW, source code is the actual program assembly files/modules/etc created by the original developer.  Most often, these files are lost forever when a company ceases development...reappearing only when some backup copy or printout was forgotten about in some programmer's attic.

 

A disassembly is an attempted reconstruction of an assembly file, created by examining a programs' binary cartridge or disk data...and translating those bytes back into assembly mnemonic instructions, arguments, and data tables.

 

Reverse-engineering takes the disassembly process one step further, replacing generic labels with descriptive names and adding comments explaining what the program lines are doing.  Depending on the complexity of the program, this process could take a very long time for even an accomplished programmer to decipher.  And even then, the original programmers' comments and label names are unrecoverable.

 

By contrast, a beginning disassembly file can be generated automatically using a program disassembler...requiring only minimal human assistance (to correctly separate program code from data tables).  I never attempted Colecovision disassembly, but dZ80 is supposed to have a good rep.

http://www.inkland.org.uk/dz80/

This is what disassembly got me. It doesn't make any sense compared to the assembly programming I've read, though. Any idea what the joypad mappings are for N, S, E, W?

Centipede.asm

[Swami]

After doing a lot of looking around, this supposedly a better disassembly using BlueMSX: Any idea what the joypad mappings are for N, S, E, W? This is probably becoming more for the programming section now, so apologies on that.

centipede2.asm

[+nanochess]

Just noticed that BlueMSX has bugs in the disassembly. Anyway I gave a peek. Also I prefer $ instead of # for hexadecimal.

 

At #a0a8 it saves the current state of controller into #60a6 with inverted bits (so bit set to 1 = push). It could be enough to change this routine if you want to change mappings.

 

At #853e it calls the routine to read the controller and saves value still in A also into register C.

 

At #8561 it starts testing the C register for movements

 

#8565 bit 0,a = test for left

#8572 bit 2,a = test for right

#857f bit 3,a = test for up

#858c bit 1,a = test for down

 

At #85ae bit 3,(hl) = test for up but using #60a6.

At #85d9 bit 0,(hl) and bit 2,(hl) = test for left/right using #60a6.

 

[Swami]

2 hours ago, nanochess said:

Just noticed that BlueMSX has bugs in the disassembly. Anyway I gave a peek. Also I prefer $ instead of # for hexadecimal.

 

At #a0a8 it saves the current state of controller into #60a6 with inverted bits (so bit set to 1 = push). It could be enough to change this routine if you want to change mappings.

 

At #853e it calls the routine to read the controller and saves value still in A also into register C.

 

At #8561 it starts testing the C register for movements

 

#8565 bit 0,a = test for left

#8572 bit 2,a = test for right

#857f bit 3,a = test for up

#858c bit 1,a = test for down

 

At #85ae bit 3,(hl) = test for up but using #60a6.

At #85d9 bit 0,(hl) and bit 2,(hl) = test for left/right using #60a6.

 

Thanks nanochess. Your the best! It seems no utility gives a very good disassembly, but BlueMSX is supposedly better than dz80. I found it confusing because manuals listed bits 5-8 as joypad, but  I may not understand the context.