VMS Help MACRO, VAX MACRO Assembler, Instructions, BLBx  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Purpose:        Branch on low bit - test bit
    Format:         opcode src.rl,displ.bb
    Operation:      teststate = if {BLBS} then 1 else 0; if src<0>
                    EQL teststate then PC = {PC + SEXT (displ)}
    C. Codes:       Not affected
    Exceptions:     None
    Opcodes:        E8    BLBS     Branch on low bit set
                    E9    BLBC     Branch on low bit clear
    Description:    The LSB of src is tested and if it is equal to the
                    test state indicated by the instruction, the branch
                    is taken.