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

    Purpose:        Branch to subroutine - transfer control to subroutine
    Format:         opcode displ.bx
    Operation:      -(SP) = PC; PC = {PC + SEXT (displ)}
    C. Codes:       Not affected
    Exceptions:     None
    Opcodes:        10    BSBB     Branch to sub., byte displ.
                    30    BSBW     Branch to sub., word displ.
    Description:    PC is pushed onto the stack as a longword and the
                    branch is taken.