ABSENTRY Port1
RAMStart EQU $0400
ROMStart EQU $E000
StartVector EQU $FFFE
PRTB EQU $01
DDRB EQU $03
PUCR EQU $0C
     ORG $E800
     DC.B $F0,$90,$60,$00
          ORG  ROMStart
Port1
           MOVB #$F0,DDRB
           BSET PUCR,$02

START  LDAA #$E8
       LDAB PRTB
       ANDB #$03
       XGDX
       LDAB ,X
       COMB
       STAB PRTB
       JMP START
       ORG StartVector
       DC.W Port1