DEC
8-bit Arithmetic Group | 16-Bit Arithmetic Group
Expansion:
DECrement
Usage:
dec {r|rr}
Decreases register by 1
| Instruction | Description | Opcode |
|---|---|---|
| DEC A | Decrease register A by 1 | 3D |
| DEC B | Decrease register B by 1 | 05 |
| DEC C | Decrease register C by 1 | 0D |
| DEC D | Decrease register D by 1 | 15 |
| DEC E | Decrease register E by 1 | 1D |
| DEC H | Decrease register H by 1 | 25 |
| DEC L | Decrease register L by 1 | 2D |
| DEC HL | Decrease register HL by 1 | 2B |
| DEC BC | Decrease register BC by 1 | 0B |
| DEC DE | Decrease register DE by 1 | 1B |
| DEC IX | Decrease register IX by 1 | DD2B |
| DEC IY | Decrease register IY by 1 | FD2B |
| DEC SP | Decrease Stack Pointer register by 1 | 3B |
| DEC (HL) | Decrease value at memory address held in register (HL) by 1 | 35 |
| DEC (IX+{??}) | Decrease value at address in register IX + displacement offset by 1 | DD35 {??} |
| DEC (IY+{??}) | Decrease value at address in register IY + displacement offset by 1 | FD35 {??} |
Example
; Example
ld a, 5 ; move the value 5 to reg A
dec a ; dec a register by 1