TMR0 overflow problem

[paul borgmeier]

Runtimer:

TMR0ON = 1
TMR0IF = 0

IF TMR0IF = 1 THEN HIGH PORTB.4

GOTO Main

Your polling technique has holes. When you enter Runtimer, you clear the flag and turn the timer on. If it has not overflowed, you go to main and spend a lot of time talking to your LCD ... then you turn the timer off. If the TMR0 overflows while in the LCD routine (odds are that this is where it will overflow), you clear the flag right before polling. Change to something like this:

Runtimer:

TMR0ON = 1

IF TMR0IF = 1 THEN 
	HIGH PORTB.4
	TMR0IF=0		' clear flag after you have trapped it
ENDIF

GOTO Main