DEC 16-bit Decrement
Decrement 16-bit register pair
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
|---|---|---|---|---|---|---|---|---|
| \(dd \longleftarrow dd - 1\) | ||||||||
| DEC dd | ||||||||
| 0 | 0 | dd | 1 | 0 | 1 | 1 | ||
| \(IX \longleftarrow IX - 1\) | ||||||||
| DEC IX | ||||||||
| 1 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | DD |
| 0 | 0 | 1 | 0 | 1 | 0 | 1 | 1 | 2B |
| \(IY \longleftarrow IY - 1\) | ||||||||
| DEC IY | ||||||||
| 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | FD |
| 0 | 0 | 1 | 0 | 1 | 0 | 1 | 1 | 2B |
| Value | dd |
|---|---|
| 00 | BC |
| 01 | DE |
| 10 | HL |
| 11 | SP |
Flags Affected
| None. |
Opcode Matrix
| BC | DE | HL | SP | IX | IY | |
|---|---|---|---|---|---|---|
| Op |
DEC BC
0B16 |
DEC DE
1B16 |
DEC HL
2B16 |
DEC SP
3B16 |
DEC IX
DD2B210 |
DEC IY
FD2B210 |
|
Instruction
Opcode hexSize bytesCycle count
| Register |
Last modified November 16, 2021: Add flags to math operations (63d34c2)