Hi,

I recently started using the 8052. Some simple programming to experiment works fine.
Now I'm using the INT0 interrupt. I use no external
memory so EA is strapped to VCC reset is held low by a 1k resistor and a 50 Hz TTL pulse is applied to the INT0 pin.
The interrupt increments a register , divides it by 50 and places the result in another register.
Outside the interrupt the result is placed at P0.
The interrupt is edge triggered.

The problem:

When I'm looking at output of P0 with my oscilloscope
I see at the background a parasitic pulse, this pulse
occurs at the falling edge of the 50Hz pulse.
Does anyone know where this is comming from? It looks
like it is a division of the clock freqency.