LDC        RD, immediate-2                                                     ; "0" : - R D -   0 0 . .
           RD, immediate-18                                                    ; "0" : - R D -   1 0 . .  ++ immediate

SHIFT+LDC  RD, immediate-2                                                     ; "0" : - R D -   0 1 . .
           RD, immediate-18                                                    ; "0" : - R D -   1 1 . .  ++ immediate
                                                                               ;                 
                                                                               ;          "long immediate"
                                                                               ;                   
                                                                               ;              command number
                                                                               ;                      
                                                                               ;                short immediate
