Hutchison, Guy

M. Harte, Howard

TV80

Instruction DJNZ fails like this:

ADDR  Instruction
------------------
00E6  ld bc,$0000
00E9  djnz $00E9
00EB  di
00EC  dec c
00ED  jr nz,$00E9

TV80 does not loop around 00E9 but just continues on to 00EB.

I simulated this with iVerilog. I can provide waveforms if you contact me.

Thanks.

DJNZ/DEC fails

Undocumented instructions like RL (IX+1),E are not supported by TV80.

In real Z80 all instructions under CB can be prefixed by DD/FD. In result will be operation like: OP (II+d),r, where II is IX or IY, d - offset (-128...+127), r one of standard registers (A, B, C, D, E, H, L). This operations do something like:
ld r,(II+d)
OP r
ld (II+d),r

OP can be: RLC, RL, RRC, RR, SLA, SRA, SRL, SLL, BIT, SET, RES

OpCode: DD CB dd oo, there CB oo is code of "OP r" operation.

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