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GB-Z80
From Sonic Retro
The "GB-Z80" is Nintendo's rendition of Zilog's Z80 processor core used in the Game Boy. Compared to a vanilla Z80, some instructions have been added, and some removed to better suit the hardware.
Added instructions include:
STOP LD (HLI),A LD (HLD),A LD A,(HLI) LD A,(HLD) LD ($FF00+nn),A LD ($FF00+C),A LD A,($FF00+nn) LD A,($FF00+C) LD (nnnn),SP LD HL,SP+nn ADD SP,nn SWAP r
Removed instructions include:
- Anything utilizing the IX or IY registers
- Exchange instructions.
- Conditional jumps/calls/rets on parity/overflow and sign flag.
- No IN/OUT instructions
- Commands prefixed with ED (not remapped RETI).
Reassigned Opcodes:
LD A,[nnnn] LD [nnnn],A RETI
External Links
More information can be found in The GBDevrs scene.


