pic16f886 / mplab help with bsf PORTC

Discussion in 'Embedded Systems and Microcontrollers' started by DMCCOY, Mar 8, 2009.


    Thread Starter New Member

    Mar 8, 2009
    Hello, I have searched here and elsewhere for the answer to my question but I cannot seem to find it. :confused: I am tyrying to make an 8 bit LED bar graph scroll to the left. But, it only is to shift one time left before returning to main. LED_Location is a variable I have set to keep track of my LED position. Once the count in LED_Location gets to d'8' I have it reseting the count to zero since my leds are 0-7.

    It currently is working like a counter, my LED output on PORTC is from what I understand taking the number from LED_Location and representing it in binary dislpay.

    What I am trying to accomplish is only one LED is on at a time, and if my value from LED_Location is 1, then I need only PORTC bit1 on, if my value from LED_Location is 3, I need only PORTC bit 3. Right now if LED_Location is 3, im getting PORTC bit1 and bit2 lit up for the b'3' value....

    Heres what I have

    ; Shifts LEDs left one position, to scroll left led location output shifts from 'd' value
    ; 0 and shifts upward, ie 0,1,2....7, then resets to 0

    clrf PORTC ; Clears previous LED
    incf LED_Location,f ; adds 1 to previous LED value to scroll left
    btfsc LED_Location,3 ; tests if decimal value is 8,there is no led8
    clrf LED_Location ; if decimal value is 8 Led location is reset to zero
    movf LED_Location,W
    movwf PORTC ; led is now lit up depending on value

    My problem is the movwf PORTC, I need to bsf PORTC (what ever bit is represented by the value of LED_Location)

    Any suggestions???
    Last edited: Mar 8, 2009
  2. thatoneguy


    Feb 19, 2009
    Work with it in binary, using the rollleft instruction.

    movlw 1
    movwf PORTC
    Call Delay
    rlf PORTC, 1 ; Roll PORTC Left 1 Position, from w through carry
    goto Roll

    Port C would proceed like this:

    Is that the desired result?

    Substituting just the rlf in where you need it will roll the contents of the register left the number of positions you specify, wrapping around through w and carry, so the 0/all off would be when the single bit above is in the carry bit.

    In an application that does more than just the above, save w, save carry, set to w PORTC, roll 1 position, restore w and carry. Otherwise w contents will be rolled and odd stuff will happen to both what w was supposed to be, and the display (PORTC). :)