ZiLOG eZ80

eZ80
®
CPU
User Manual
UM007714-0908 CPU Instruction Set
135
DEC (IX/Y+d)
Decrement
Operation
(IX/Y+d) ← (IX/Y+d)–1
Description:
The ( IX/Y + d ) operand is the 8-bit value stored in the memory location specified by the
contents of the Index Register, IX or IY, added to the two’s-complement displacement
d .
This 8-bit value contained in the specified register is decremented by 1.
Condition Bits Affected
Attributes
S Set if result is negative; reset otherwise.
Z Set if result is 0; reset otherwise.
H Set is borrowed from bit 4; reset otherwise.
P/V Set if operand was 80h before operation; reset otherwise.
N Set.
C Not affected.
Mnemonic Operand ADL Mode Cycle Opcode (hex)
DEC (IX+d)X 6 DD, 35, dd
DEC.S (IX+d)1 7 52, DD, 35, dd
DEC.L (IX+d)0 7 49, DD, 35, dd
DEC (IY+d)X 6 FD, 35, dd
DEC.S (IY+d)1 7 52, FD, 35, dd
DEC.L (IY+d)0 7 49, FD, 35, dd