Atmel AVR

48. COM – One’s Complement
48.1. Description
This instruction performs a One’s Complement of register Rd.
Operation:
(i) Rd ← $FF - Rd
Syntax: Operands: Program Counter:
(i) COM Rd 0 ≤ d ≤ 31 PC ← PC + 1
16-bit Opcode:
1001 010d dddd 0000
48.2. Status Register (SREG) and Boolean Formula
I T H S V N Z C
– – – ⇔ 0 ⇔ ⇔ 1
S N ⊕ V, for signed tests.
V 0
Cleared.
N R7
Set if MSB of the result is set; cleared otherwise.
Z R7 • R6 • R5 • R4 • R3 • R2 • R1 • R0
Set if the result is $00; cleared otherwise.
C 1
Set.
R (Result) equals Rd after the operation.
Example:
com r4 ; Take one’s complement of r4
breq zero ; Branch if zero
...
zero: nop ; Branch destination (do nothing)
Words 1 (2 bytes)
Cycles 1
Atmel AVR Instruction Set Manual [OTHER]
Atmel-0856L-AVR-Instruction-Set-Manual_Other-11/2016
76