PIACA   EQU     $8001
PIADDA  EQU     $8000
PIADA   EQU     $8000
INTRP   EQU     $0100

        ORG     $0000
        LDS     #$100       START STACK AT MEMORY LOCATION
                        *   00FF
        CLR     $40         CLEAR DATA READY FLAG
        CLR     PIACA       ADDRESS DATA DIRECTION REGISTER
        CLR     PIADDA      MAKE ALL DATA LINES INPUTS
        LDA     #%00000101  ENABLE KEYBOARD INTERRUPT
        STA     PIACA       ON PIA
        ANDCC   #%11101111  ENABLE CPU INTERRUPT
WTRDY   TST     $40         IS THERE DATA FROM THE KEYBOARD?
        BEQ     WTRDY       NO, WAIT
        SWI                 YES, PROCEED
        .DW     $113E   BREAK
LOOP    JMP     LOOP    LOOP HERE
        END



        ORG     INTRP
        INC     $40         SET DATA READY FLAG
        LDA     PIADA       FETCH DATA FROM KEYBOARD
        STA     $41         SAVE DATA IN MEMORY
        .DW     $113E   BREAK
        RTI



TLOOP   JMP         WTRDY


        END