[A89] Re: A Night's Pondering...

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[A89] Re: A Night's Pondering...


>
> it would be interesting to see whether or not it could emulate in real
time.
> i think the only difference between the gameboy's processor and the z80
are
> the scrolling registers and the sound registers, also i dont know if its
rom

No, that isn't right.  It's been a while since I last worked on any GBC asm
but, there are more differences than that.  Since that is so, I copied the
following straight out of the Pan Doc...

The following are added instructions:

  ADD  SP,nn             ;nn = signed byte
  LDI  (HL),A            ;Write A to (HL) and increment HL
  LDD  (HL),A            ;Write A to (HL) and decrement HL
  LDI  A,(HL)            ;Write (HL) to A and increment HL
  LDD  A,(HL)            ;Write (HL) to A and decrement HL
  LD  A,($FF00+nn)
  LD  A,($FF00+C)
  LD  ($FF00+nn),A
  LD  ($FF00+C),A
  LD  (nnnn),SP
  LD  HL,(SP+nn)         ;nn = signed byte
  STOP                   ;?
  SWAP r                 ;Rotate register r by 4 bits

 The following instructions have been removed:

  Any command that uses the IX or IY registers.
  All IN/OUT instructions.
  All exchange instructions.
  All commands prefixed by ED (except remapped RETI).
  All conditional jumps/calls/rets on parity/overflow and sign flag.

 The following instructions have different opcodes:

  LD  A,[nnnn]
  LD  [nnnn],A
  RETI

Also, there is no ldir command.

Glenn Murphy
References: