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Emu Author
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Discussion Starter · #1 ·
well, i decided to take a swing at doing the gameboy now, though after reading about the troubles people had with it at emutalk, i know i am in for a long ride with this one but i think its possible to get something done on it, so wish me luck.
 

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Discussion Starter · #3 ·
yea lol, i have 2 emus under my belt now, time to get working on something that is a real challenge :D. i already have a basic gui setup, with basic video output capability for when i actually get something to display lol.
 

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Emu Author
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Discussion Starter · #8 ·
well it would maybe depend on how fast i can start knocking things out with this emu, coding opcodes so far have not seemed to difficult i think really the difficult part is just timing things correctly really. though at some point i really need to look into properly using direct sound lol.
 

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well I started a GB emulator yesterday. I have most of the opcodes in... missing a few like push/pop/rst. Quick question, I read that the GB has a few more instructions than the 8080... anyone know what there opcodes are? And does it use some (or any) of the Z80 extended instructions. I keep reading that it is more similor to the Z80 but doesn't use any instructions from it XD

Hoping to have afew 32kB games showing garbage in a few weeks. :D
 

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well I started a GB emulator yesterday. I have most of the opcodes in... missing a few like push/pop/rst. Quick question, I read that the GB has a few more instructions than the 8080... anyone know what there opcodes are? And does it use some (or any) of the Z80 extended instructions. I keep reading that it is more similor to the Z80 but doesn't use any instructions from it XD

Hoping to have afew 32kB games showing garbage in a few weeks. :D
It's a modified Z80 AFAIK. Anyway, here's an opcode decoder for your convenience:

Decoding Z80 Opcodes

Following that would be much faster than branching out all byte codes you can imagine... :innocent:

Note that the encoding of opcodes on the Gameboy is slightly different but only for a few opcodes. Aside from that, the rest retains their original use.
 

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Well I made a little progress this week. I have Tetris loading and running without it crashing. Seems it doesnt use any Z80 instructions so far because I don't have those implemented (the rot ops).

Specifications
This doc looks significantly better than what I was using so hopefully this will get me going again. need to look at graphics now to see if I can get anything to output. (but ill probably have to do flags and interrupts first XD)
 

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You're already dead...
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yeah i used that nocash website for my nes emu.
the guy wrote some good docs.
 

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Emu Author
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Discussion Starter · #18 ·
after quite a bit of work today i finally have something to show for my efforts since i started this project, and that being the bootstrap loads now, visually it looks ok but i have bugs that are obviously stopping much else from working. i am starting out testing with asteroids but it wont load past the boot strap for now but that will change soon i am sure :D.
 

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great job :thumb:
 

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Emu author
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after quite a bit of work today i finally have something to show for my efforts since i started this project, and that being the bootstrap loads now, visually it looks ok but i have bugs that are obviously stopping much else from working. i am starting out testing with asteroids but it wont load past the boot strap for now but that will change soon i am sure :D.
Are you remapping the first 0x100 bytes to the ROM when $FF50 is written to by the bootstrap?
 
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