Hi:

My clock program uses an ISR triggered from Timer2 once every 1.0 ms.  
In the ISR there is code that turns on an LED at the top of the second 
and turns it off after 10 ms.  I'd like to use the LED for debugging and 
so commented out the two lines that control the LED, but after doing 
that the LCD display turned to garbage.  It turns out that placing a 
"banksel PORTB" at the end of the ISR fixes the problem when the LED 
code is commented out.  But I don't understand why? 

Have Fun,

Brooke Clarke

Here is the end of the ISR code:

End_ISR   
  movlw .10    ; 10 ms on (1 ms is too short)
  subwf    ms_counter,W
  btfsc STATUS,Z
  banksel PORTB ; NEED banksel here or bcf PORTB,7 WHY-O-WHY
; bcf    PORTB,7    ; heart beat off PC4 Testing Switches <<<needed 
inorder to work,
; commenting out the bsf and bcf lines causes the clock to
; have garbled display.  Why?
; --- pop pclath, status & w ---
  movf  PCLATH_TEMP,W
  movwf  PCLATH
  swapf    STATUS_TEMP,W
  movwf STATUS
  swapf W_TEMP,F
  swapf    W_TEMP,W
  retfie    ; turns on GIE
;================== End of ISR ===========================

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