Zilog Z08470 - Manual (Page 180)

Z80 Instruction Set UM008007-0715
168
Z80 CPU
User Manual
DEC m
Operation
m ← m – 1
Op Code
DEC
Operand
m
The m operand is any of r, (HL), (IX+d), or (lY+d), as defined for the analogous INC
instructions. These possible op code/operand combinations are assembled as follows in
the object code:
r identifies registers B, C, D, E, H, L, or A assembled as follows in the object code field:
Register r
B 000
C 001
D 010
E 011
H 100
L 101
A 111
0 0 r 0 1 1
0 0 1 0 1 1 1 0 35
1 1 1 0 1 1 0 1 DD
0 0 1 0 1 1 1 0 35
1 1 1 0 1 1 1 1 FD
0 0 1 0 1 1 1 0 35
DEC (HL)
DEC (IX+d)
DEC (IY+d)
d
d
DEC r*