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

    Purpose:        Extract field - moves bit field to integer
    Format:         opcode pos.rl,size.rb,base.vb,dst.wl
    Operation:      EXTV:  dst = if size NEQU 0 then SEXT (
                                   FIELD (pos, size, base)) else 0
                    EXTZV: dst = if size NEQU 0 then ZEXT (
                                   FIELD (pos, size, base)) else 0
    C. Codes:       N = {dst LSS 0}, Z = {dst EQL 0}, V = 0, C = C
    Exceptions:     Reserved operand
    Opcodes:        EE    EXTV     Extract field, sign extend
                    EF    EXTZV    Extract field, zero extend
    Description:    For EXTV, dst is replaced by the sign-extended field
                    specified by pos, size and base. For EXTZV, dst is
                    replaced by the zero-extended field specified by pos,
                    size and base. If size is 0 dst is replaced by 0.