GameBoy CP/M?
Kelli Halliburton
I don't know much else about the internals of the system. I do know that
there's no keyboard and no text mode for the screen. I propose the interlink
port be appropriated for attaching to a console. A fairly nice CP/M BIOS and
CCP could be burned onto a cartridge, with plenty of room left over for
utilities. Any thoughts?
Steve
It's not a true Z-80, but one of those japanese 780's with a very
similar instruction set. The 8085 is a subset set without SID and SOD, I
believe.
-Steve
--
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Steve
>
> On Sat, 25 Nov 2000 00:10:16 -0800, Steve <rst...@armory.com> wrote:
>
> >It's not a true Z-80, but one of those japanese 780's with a very
> >similar instruction set. The 8085 is a subset set without SID and SOD, I
> >believe.
> >-Steve
>
> however I was told it was a NEC 7800, a different animal. The 7800
> (actually 78xx) is archected like z80 register set but instruction
> set is very different. Or it could be like the rabbit, z80 like but
> not compatable.
>
> Allison
-----------------------------
Ah, I thought those were the same, and I thought that it used some
unsupported undocumented couple of commands as an intricate part of the
gameboy system. Are you SURE the D780 is exactly a Z-80, cause I've got
a pile of them I had thought might not be a good idea to use!
nos...@nouce.bellatlantic.net
nos...@nouce.bellatlantic.net
>Ah, I thought those were the same, and I thought that it used some
>unsupported undocumented couple of commands as an intricate part of the
>gameboy system. Are you SURE the D780 is exactly a Z-80, cause I've got
>a pile of them I had thought might not be a good idea to use!
>-Steve
>--
>-Steve Walz rst...@armory.com ftp://ftp.armory.com/pub/user/rstevew
I was product engineer for NEC back in the early 80s. I know the D780
well, I also have several tubes of them. The part is a functionally
accurate to the Z80 down to all of the hidden instructions, it is not
a mask swap however.
There are two other designs out there that are NOT z80 NOR D780
I think the gameboy is one and the other is the RABBIT.
The NEC D78xx commonly seen as 78PG11 and friends is a z80
like cpu with analog and digital IO. It's is a rom (or piggy back)
based single chipper. While it's register set if very z80 like the
instruction set is not even close.
Allison
Shawn Sijnstra
Steve wrote:
>
> It's not a true Z-80, but one of those japanese 780's with a very
> similar instruction set. The 8085 is a subset set without SID and SOD, I
> believe.
> -Steve
> --
According to
http://www.gamehunt.com/cheat/Nintendo_Gameboy/cheat2861.html
the differences are:
3. GameBoy CPU:
As it appears, the CPU used in GameBoy is not exactly
Z80. Some of Z80
instructions and registers are missing while others are
added:
* The "shadow" set of registers [BC',DE',HL',AF'] and
the index registers
[IX,IY] are missing and, consequently, there are no DD
and FD opcode tables.
* I/O ports are gone and so are all IN/OUT opcodes.
* HALT is interrupted even when interrupts are disabled.
* Following Z80 opcodes are changed:
------------------------------------------------------------------------------
Code Z80 operation GameBoy operation
------------------------------------------------------------------------------
08 xx xx EX AF,AF' LD (word),SP Save SP at given address
10 xx DJNZ offset STOP Meaning unknown
22 LD (word),HL LD (HLI),A Save A at (HL) and increment
HL
2A LD HL,(word) LD A,(HLI) Load A from (HL) and
increment HL
32 LD (word),A LD (HLD),A Save A at (HL) and decrement
HL
3A LD A,(word) LD A,(HLD) Load A from (HL) and decrement
HL
D3 OUTA (byte) No operation
D9 EXX RETI Enable interrupts and return
DB INA (byte) No operation
DD Prefix DD No operation
E0 xx RET PO LD (byte),A Save A at (FF00+byte)
E2 JP PO,word LD (C),A Save A at (FF00+C)
E3 EX HL,(SP) No operation
E4 CALL PO,word No operation
E8 xx RET PE ADD SP,offset Add signed offset to SP
EA xx xx JP PE,word LD (word),A Save A at given address
EB EX DE,HL No operation
EC CALL PE,word No operation
F0 xx RET P LD A,(byte) Load A from (FF00+byte)
F2 JP P,word No operation
F4 CALL P,word No operation
F8 xx RET M LDHL SP,offset Load HL with SP + signed
offset
FA xx xx JP M,word LD A,(word) Load A from given address
FC CALL M,word No operation
FD Prefix FD No operation
------------------------------------------------------------------------------
Cheers,
Shawn
Steve
>
> On Sat, 25 Nov 2000 21:36:15 -0800, Steve <rst...@armory.com> wrote:
>
> >Ah, I thought those were the same, and I thought that it used some
> >unsupported undocumented couple of commands as an intricate part of the
> >gameboy system. Are you SURE the D780 is exactly a Z-80, cause I've got
> >a pile of them I had thought might not be a good idea to use!
> >-Steve
> >--
> >-Steve Walz rst...@armory.com ftp://ftp.armory.com/pub/user/rstevew
>
> I was product engineer for NEC back in the early 80s. I know the D780
> well, I also have several tubes of them. The part is a functionally
> accurate to the Z80 down to all of the hidden instructions, it is not
> a mask swap however.
Goody! I've got a pile of them! I shall make an annotation upon them
that you said so!
> There are two other designs out there that are NOT z80 NOR D780
> I think the gameboy is one and the other is the RABBIT.
>
> The NEC D78xx commonly seen as 78PG11 and friends is a z80
> like cpu with analog and digital IO. It's is a rom (or piggy back)
> based single chipper. While it's register set if very z80 like the
> instruction set is not even close.
>
> Allison
----------------
Thanks!
-Steve
--
-Steve Walz rst...@armory.com ftp://ftp.armory.com/pub/user/rstevew