ZiLOG eZ80 User Manual

eZ80
®
CPU
User Manual
UM007714-0908 CPU Instruction Set
124
CPD
Compare and Decrement
Operation
A–(HL)
HL ← HL – 1
BC ← BC – 1
Description
The CPU compares the contents of the accumulator, A, to the memory location that the
HL register points to, and outputs the difference. This instruction does not affect the con-
tents of the reference memory location or the accumulator. The HL and BC registers dec-
rement.
Condition Bits Affected
Attributes
S Set if result is negative; reset otherwise.
Z Set if A = (HL); reset otherwise.
H Set if borrow from bit 4; reset otherwise.
P/V Set if BC – 1 ≠ 0; reset otherwise.
N Set.
C Not affected.
Mnemonic Operand ADL Mode Cycle Opcode (hex)
CPD —X 3ED, A9
CPD.S —1 452, ED, A9
CPD.L —0 449, ED, A9

ZiLOG eZ80 Specifications

General

Brand	ZiLOG
Model	eZ80
Category	Computer Hardware
Language	English