Zilog Z80380 - Manual (Page 79)

5-45
Z380 ™
U SER ' S M ANUAL Z ILOG
DC-8297-03
DEC[W]
DECREMENT (WORD)
DEC[W] dst dst = R, RX
Operation: if (XM) then begin
dst(31-0)
←
dst(31-0) - 1
end
else begin
dst(15-0)
←
dst(15-0) - 1
end
The destination operand is decremented by one and the result is stored in the destination.
Two’s complement subtraction is performed. Note that the length of the operand is
controlled by the Extended/Native mode selection, which is consistent with the manipulation
of an address by the instruction.
Flags: S: Unaffected
Z: Unaffected
H: Unaffected
V: Unaffected
N: Unaffected
C: Unaffected
Addressing Execute
Mode Syntax Instruction Format Time Note
R: DEC[W] R 00rr1011 2 X
RX: DEC[W] RX 11y11101 00101011 2 X
Field Encodings: rr: 00 for BC, 01 for DE, 10 for HL, 11 for SP
y:
0 for IX, 1 for IY