DEC
DECREMENT
DEC
Operation: | Flags Affected: |
(DEST) +- | AF, OF, PF, SF, ZF |
Description:
DEC (Decrement) subtracts one from the destination operand. The operand may be a byte or a word and is treated as an unsigned binary number (see AAA and DAA). DEC updates AF, OF, PF, SF and ZF; it does not affect CF.
Encoding:
Memory or Register Operand:
11111 11 1 w 1mod 001 rIm 1
DEST= EA
16-Bit Register Operand:
1 01 001 reg
DEST= REG
DEC Operands Clocks* Transfers Bytes DEC Coding Example
reg16 | 2 | - | 1 | DECAX |
reg8 | 3 | - | 2 | DECAL |
memory | 15(23)+ EA | 2 | DEC ARRAY [SI] |
*b(w): where b denotes the number of clock cycles for byte operands and w denotes the number of clock cycles for word operands.
