ZiLOG Z80380 User Manual page 78

Z
ILOG
DEC
DECREMENT (BYTE)
DEC dst
dst ← dst – 1
Operation:
The destination operand is decremented by one and the result is stored in the destination.
Two's complement subtraction is performed.
Flags: S: Set if the result is negative; cleared otherwise
Z: Set if the result is zero; cleared otherwise
H: Set if there is a borrow from bit 4 of the result; cleared otherwise
V: Set if arithmetic overflow occurs, that is, if the destination was 80H; cleared otherwise
N: Set
C: Unaffected
Addressing
Mode Syntax
R: DEC R
RX: DEC RX
IR: DEC (HL)
DEC (XY+d)
X:
Field Encodings: r: per convention
y: 0 for IX, 1 for IY
w: 0 for high byte, 1 for low byte
Note: 2 for accumulator, 3 for any other register
5-44
dst = R, RX, IR, X
Instruction Format
00-r-101
11y11101 0010w101
00110101
11y11101 00110101 ——d—
Execute
Time Note
note
2
2+r+w
4+r+w I
Z380 ™
U ' M
SER S ANUAL
DC-8297-03