I'm trying to track down the source of a glitch that's occurring on one of the digital output lines on a 16F630. When there is no significant load on the pin, it works fine. However, as the resistive load is increased closer to the line's maximum allowable current of 25 mA, strange things start to happen. On 0 to 1 transitions, there appears to be what looks like ringing. It's actually a series of evenly spaced pulses which suspiciously appear to mimic an output signal that's on another digital output line on a different port. I should point out that the total I/O current draw for all I/O lines is within spec.
I'm not totally convinced that this is crosstalk, but I haven't ruled it out either. Debugging the problem is a bit tricky at the moment, because the device is at a customer's site several hundred miles away. I'm relying on tests that their technical staff are able to carry out. I have some scope traces, but can't play with it in real time at the moment.
Just wondering if anyone else has experienced similar erratic behaviour on output lines.
I'm not totally convinced that this is crosstalk, but I haven't ruled it out either. Debugging the problem is a bit tricky at the moment, because the device is at a customer's site several hundred miles away. I'm relying on tests that their technical staff are able to carry out. I have some scope traces, but can't play with it in real time at the moment.
Just wondering if anyone else has experienced similar erratic behaviour on output lines.