external interrupt for timer0 in PIC16F877A (urgent)

[sana_akhtar]

Hey

I am trying to start timer on the positive transition from external source like when I push the button, timer start counting.
The code I wrote works well with internal instruction clock but not from external source. I am really frustrated for not figure out whats wrong with this. Can someone please help me out. Please?

 

[kripacharya]

A typical push-button generates multiple transitions when you press it. This is known as 'switch bounce'

So either by circuitry (usually a R and C connected properly) or by means of clever software code, you have to 'de-bounce' your switch before it can be meaningfully used.

You can google these terms and see what you find.