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

    Purpose:        Insert field - moves integer to bit field

    Format:         opcode src.rl,pos.rl,size.rb,base.vb
    Operation:      if size NEQU 0 then FIELD (pos, size, base) =
                      src <{size -1 }>
    C. Codes:       Not affected
    Exceptions:     Reserved operand
    Opcode:         F0    INSV     Insert field
    Description:    The field specified by pos, size and base is
                    replaced by bits {size-1}:0 of src. If size is 0
                    no action occurs.