Table of Contents
Previous topic Next topic
MICROPROCESSOR INSTRUCTION REFERENCE->DEC
DEC m Decrement operand m
m <- m - 1
Flags
| S | Set if result -ve, else cleared |
| Z | Set if result zero, else cleared |
| H | Set if half carry, else cleared |
| P/V | Set if overflow, else cleared |
| N | Set always |
| C | Not affected |
| m: | No of | M | T | usec @ |
| bytes | cycles | states | 2 MHz |
|
| r | 1 | 1 | 4 | 2 |
| (HL) | 1 | 3 | 11 | 5.5 |
| (IX+d) | 3 | 6 | 23 | 11.5 |
| (IY+d) | 3 | 6 | 23 | 11.5 |
r may be one of A,B,C,D,E,H,L
DEC pp Decrement operand pp
pp <- pp - 1
Flags
| S | Not affected |
| Z | Not affected |
| H | Not affected |
| P/V | Not affected |
| N | Not affected |
| C | Not affected |
| pp: | No of | M | T | usec @ |
| bytes | cycles | states | 2 MHz |
rr may be one of BC, DE, HL or SP