Hello...

scroll down...

In a message dated 2/6/00 7:17:22 PM Pacific Standard Time,
sseyedi@HYPERVR.COM writes:

> Hello,
>  RE: PIC16F84
>  I am still working on this piece of code and to me it fully makes sense.
But
>  the thing wont work. None of the LEDs get lit with the input. I tried it on
>  the MLAB simulator and it seems to be doing what I want it to do!
>
>  Anybody see the problem? (or maybe have code for reading a button (or a set
>  of), debounce them and light an LED accordingly, this might actually be
more
>  faster?!).
>
>
>  ------
>  #include "p16f84.inc"
>
>          LIST P=16F84, R=DEC
>
>
>          ;  Register Usage
>          CBLOCK 0x20                   ;  vars to use for the delay loop
>                  LoopCntr1,LoopCntr2
>          ENDC
>
>
>          __CONFIG _CP_OFF & _XT_OSC & _PWRTE_ON  & _WDT_OFF
>          ;  Note that the WatchDog Timer is OFF
>          ;  ** the RC oscillator does not work for some reason with an rc
>  oscillator?!?!
>          ;     the funny thing is that the xt works with it though!
>
>
>          ; Note: B0 : mommentarily on push button
>          ;       B1 : lit at all times!
>          ;       B2 : lit if button is being pushed
>
>
>          ORG     0
>          GOTO    Start
>
>  ; DELAY SUBROUTINE
>  ; - creates a delay by doing (for) loops
>  Delay           MOVLW   250
>                  MOVWF   LoopCntr1
>  Outer           MOVLW   110
>                  MOVWF   LoopCntr2
>  Inner           NOP
>                  NOP
>                  DECFSZ  LoopCntr2,F
>                  GOTO    Inner
>                  DECFSZ  LoopCntr1,F
>                  GOTO    Outer
>                  RETURN
>
>
>  ; MAIN PROGRAM
>  ;
>  Start
>          BSF     STATUS,RP0      ; select bank 1 (need to go to bank 1
since
> trisb is there!)
>          MOVLW   0x01            ; turn b0:input, b...:output
>          MOVWF   TRISB           ; apply it to trisb register
>          BCF     STATUS,RP0      ; select bank 0 (come back!)
>          BSF     PORTB,1         ; turn on led on B1 (and keep lit)

>
>
>  Loop
>          BTFSS   PORTB,0         ; Is the Button Pressed? (if PORTB<0>=0
then
> ... )
>          GOTO    ButtonPressed   ;  .... turn it on
>          BCF     PORTB,2         ; (else:) Turn off LED B2 off
>          GOTO    Loop

You should flip those instructions around. The BTFSS will SKIP the next
instruction if the bit tested comes out true. So, looking at your code, when
PORTB0 = 1 then it will turn off the LED. Flip the GOTO and BCF instruction
around.

>
>  ButtonPressed                   ; Button Pressed, Turn LED on
>          BSF     PORTB,2
>          CALL    Delay
>          GOTO    Loop
>
>          END                     ; end of program.
>  ------
>

Regards,

Tim Hamel

>  Thanks.
>
>  +----------------------------+
>  |  Sep Seyedi   [:{0)]       |
>  +----------------------------+