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

    Purpose:        Compare field - compare bit field to integer
    Format:         opcode pos.rl,size.rb,base.rb,src.rl
    Operation:      FIELD (pos, size, base) - src
    C. Codes:       N = {field LSS src}, Z = {field EQL src},
                    V = 0, C = {field LSSU src}
    Exceptions:     Reserved operand
    Opcodes:        EC    CMPV     Compare field
                    ED    CMPZV    Compare zero-extended field

    Description:    The field specified by pos, base and size is
                    compared with the source operand. For CMPV, src is
                    compared with the sign extended field. For CMPZV,
                    src is compared with the zero extended field. The
                    only action is to affect the condition codes.