| Hex | Mnemonic | Cycles |
|---|---|---|
| 88 | DEC A | 2 |
| 89 | DEC B | 2 |
| 8A | DEC L | 2 |
| 8B | DEC H | 2 |
| 8C | DEC BR | 2 |
| 8D ll | DEC [BR:ll] | 4 |
| 8E | DEC [HL] | 3 |
| 8F | DEC SP | 2 |
| 98 | DEC BA | 2 |
| 99 | DEC HL | 2 |
| 9A | DEC IX | 2 |
| 9B | DEC IY | 2 |
A = (8-bits) Register A
B = (8-bits) Register B
L = (8-bits) Register L
H = (8-bits) Register H
BR = (8-bits) Register BR
SP = (16-bits) Register SP (Stack Pointer)
BA = (16-bits) Register BA: (B shl 8) or A
HL = (16-bits) Register HL: (H shl 8) or L
IX = (16-bits) Register IX
IY = (16-bits) Register IY
[BR:ll] = (8-bits) Memory: (EP shl 16) or (BR shl 8) or #nn
[HL] = (8-bits) Memory: (EP shl 16) or HL
; DEC Ds
;
; Ds = Source/Destination
Ds = Ds - 1
“Destination” is decremented by 1.
Carry, Overflow, and Sign remain unchanged
; A = 0x55
DEC A
; A = 0x54 (0x55 - 1 = 0x54)
; SC = (Zero=0)
; [BR+0x88] = 0xFF
DEC [BR+$88]
; [BR+0x88] = 0xFE (0xFF - 1 = 0xFE)
; SC = (Zero=0)
; BA = 0x2997
DEC BA
; BA = 0x2996 (0x2997 - 1 = 0x2996)
; SC = (Zero=0)
; IX = 0xFFFF
DEC IX
; IX = 0xFFFE (0xFFFF - 1 = 0xFFFE)
; SC = (Zero=0)