BBC — Branch if Bit Clear

Instruction Word

Slot
Inst
6
3
6
2
6
1
6
0
5
9
5
8
5
7
5
6
5
5
5
4
5
3
5
2
5
1
5
0
4
9
4
8
4
7
4
6
4
5
4
4
4
3
4
2
4
1
4
0
3
9
3
8
3
7
3
6
3
5
3
4
3
3
3
2
3
1
3
0
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1
9
1
8
1
7
1
6
1
5
1
4
1
3
1
2
1
1
1
0
9876543210
Format x24 - 24 bit(s) 0
BBC 0101 0111
s 3210
t 3210
imm8 76543210

Assembler Syntax

BBC as, at, label

Description

(please consult the Xtensa ® Instruction Set Architecture Reference Manual for any cross references and additional information)

BBC branches if the bit specified by the low five bits of address register at is clear in address register as. For little-endian processors, bit 0 is the least significant bit and bit 31 is the most significant bit. For big-endian processors, bit 0 is the most significant bit and bit 31 is the least significant bit.

The target instruction address of the branch is given by the address of the BBC instruction, plus the sign-extended 8-bit imm8 field of the instruction plus four. If the specified bit is set, execution continues with the next sequential instruction.

The inverse of BBC is BBS.

Operation

b ← AR[t]4..0 xor msbFirst5
if AR[s]b = 0 then
	nextPC ← PC + (imm8724||imm8) + 4
endif

Exceptions

EveryInstR Group (see EveryInstR Group:)