TEMP1 = $F9
TEMP2 = $FA
TEMP3 = $FB
TEMP4 = $FC
TEMP5 = $FE
;
;Routine to replace the OS with the Shadow OS.
;
         *= $0600
;
         LDA $D20E ;IRQEN
         PHA
         LDA #$00
         STA $D40E      ;NMIEN
         STA $D20E      ;IRQEN
         STA TEMP2     
         TAY
         LDA #$40
         STA TEMP3        
         DEC $D301      ;PORTB
L0001    LDA (TEMP2),Y
         STA (TEMP4),Y     
         LDA TEMP3        
         CMP TEMP5      
         BNE L0002
         LDA TEMP2   
         CMP TEMP4       
         BEQ L0005
L0002    INC TEMP2    
         BNE L0003
         INC TEMP3       
L0003    INC TEMP4        
         BNE L0004
         INC TEMP5       
L0004    BNE L0001
L0005    INC $D301      ;PORTB
         PLA
         STA $D20E      ;IRQEN
         LDA #$40
         STA $D40E      ;NMIEN
         RTS