BB Instruction

BB Instructions

Purpose:

To branch on bit test

Format:

opcode pos.rl, base.ab, displ.bb

Operation:

teststate = if {BBS} then 1 else 0;
if FIELD(pos, 1, base) EQL teststate then: PC <- PC + sign-extended displ

Condition
Codes:

N <- N;
Z <- Z;
V <- V;
C <- C;

Exceptions:

Reserved Operand

Opcodes:

E0	BBS	Branch on bit Set
E1	BBC	Brance on bit Clear

Description:

The single bit specified by the position and base operands is tested. If it is in the test state indicated by the instruction, the sign-extended branch displacement is added to the PC and the PC is replaced by the result.

Notes:

1.: A reserved operand fault occurs if pos is greater (unsigned) than 31 and the bit is contained in a register.
2.: On a reserved operand fault, the condition codes are unpredictable.