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S3C9228/P9228 SAM88RCRI INSTRUCTION SET
6-19
DEC — Decrement
DEC dst
Operation: dst ¨ dst – 1
The contents of the destination operand are decremented by one.
Flags: C: Unaffected.
Z: Set if the result is "0"; cleared otherwise.
S: Set if result is negative; cleared otherwise.
V: Set if arithmetic overflow occurred, that is, dst value is –128(80H) and result value is
+127(7FH); cleared otherwise.
D: Unaffected.
H: Unaffected.
Format:
Bytes Cycles Opcode
(Hex)
Addr Mode
dst
opc dst 2 4 00 R
4 01 IR
Examples: Given: R1 = 03H and register 03H = 10H:
DEC R1 → R1 = 02H
DEC @R1 → Register 03H = 0FH
In the first example, if working register R1 contains the value 03H, the statement "DEC R1"
decrements the hexadecimal value by one, leaving the value 02H. In the second example, the
statement "DEC @R1" decrements the value 10H contained in the destination register 03H by
one, leaving the value 0FH.