13. BRBC – Branch if Bit in SREG is Cleared
13.1. Description
Conditional relative branch. Tests a single bit in SREG and branches relatively to PC if the bit is cleared.
This instruction branches relatively to PC in either direction (PC - 63 ≤ destination ≤ PC + 64). Parameter
k is the offset from PC and is represented in two’s complement form.
Operation:
(i) If SREG(s) = 0 then PC ← PC + k + 1, else PC ← PC + 1
Syntax: Operands: Program Counter:
(i) BRBC s,k 0 ≤ s ≤ 7, -64 ≤ k ≤ +63 PC ← PC + k + 1
PC ← PC + 1, if condition is
false
16-bit Opcode:
1111 01kk kkkk ksss
13.2. Status Register (SREG) and Boolean Formula
I T H S V N Z C
– – – – – – – –
Example:
cpi r20,5 ; Compare r20 to the value 5
brbc 1,noteq ; Branch if Zero Flag cleared
...
noteq: nop ; Branch destination (do nothing)
Words 1 (2 bytes)
Cycles 1 if condition is false
2 if condition is true
Atmel AVR Instruction Set Manual [OTHER]
Atmel-0856L-AVR-Instruction-Set-Manual_Other-11/2016
40
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