[PIC] PIC16F84A - MPLAB programming **Feedback needed **

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dannyelloko20

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Hi there again, I have another project and is your feedback is needed at this point. This is what I need to do: " Read the 4-bit Switch value and then multiply the switch value by the decimal number 100 ( D’100’). Display the results on the LEDs. Must use a loop counter (“Count”) to implement this Lab. Use the literal D’100’ to set the “Count” variable and each time thru the loop add the switch value to the accumulated “SUM”. Each time thru the loop the “Count” is decrement and when you reach 0, you are done. Use REG1 for the MS byte and REG0 for the LS byte of the SUM. When S17 is a logic “0”, display the LS byte on the LEDs and when S17 is a logic ‘1” display the MS byte.

This is what I have so far and I think it needs some debugging. I would appreciate your feedback.

Code: 
BSF   STATUS,RP0
        MOVWF   TRISB
        BCF     STATUS,RP0
        MOVWF   PORTB
        
LOOP MOVLW   0x5A
        MOVWF   REG0
        MOVLW   0x39
        BTFSS   PORTA,RA0
        ADDWF   REG0,W
        BTFSC   PORTA,RA0
        COMF    REG1,W
        GOTO   DONE
        
        BTFSC   PORTA,RA0
        ADDLW   0x01
        BTFSC   PORTA,RA0
        ADDWF   REG0,W
        MOVWF   PORTB

GOTO  LOOP

DONE  END

PD: Library for PIC16F84A is included in my program. Thank you!
 

Where do I begin? You should post the full circuit and program list if you want help.

Some obvious errors are the bottom 6 lines of code are never executed because of the GOTO DONE instruction and the W register is not set for the MOVWF TRISB instruction. The W register is not set for the MOVWF PORTB instruction (should it have been MOVF PORTB,W?), the register REG1 has not been defined or used etc. I have not checked the logic of the program as I do not see how it can work
 
Last edited:

Thanks for the feedback. This is all of it.

Code: 
#include <GENERAL.H> ; PIC library

  REG0   EQU   0x40
  REG1   EQU   0x41
		

		__CONFIG	0X3FF2		
		ORG			0X0000		
		GOTO		START
		ORG			0X0004		
		RETFIE

START   BSF     STATUS,RP0
        MOVWF   TRISB
        BCF     STATUS,RP0
        MOVWF   PORTB
        
LOOP    MOVLW   0x5A
        MOVWF   REG0
        MOVLW   0x39
        BTFSS   PORTA,RA0
        ADDWF   REG0,W
        BTFSC   PORTA,RA0
        COMF    REG1,W
        GOTO    FINISHED
        
        BTFSC   PORTA,RA0
        ADDLW   0x01
        BTFSC   PORTA,RA0
        ADDWF   REG0,W
        MOVF    PORTB
        GOTO    LOOP

FINISHED    END
 

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