Quote Originally Posted by tumbleweed View Post
Also, if you're using a crystal then probing the OSC1 and OSC2 pins is going to throw things off, and could even make it stop oscillating.
Usually with a 20M xtal you want smaller caps, not larger ones. You might get away with probing the OSC2 pin since that's the output drive...
Yeah, I noticed that rather quickly on the Lab X1. But even probing only OSC2 on both setups, it quickly became apparent something was terribly wrong with the breadboard.

I did get OSC1 to function while being probed on the X1. That's wht I wasn't really concerned when the intervals on both pins became "slightly irregular", but hey, the PIC still worked.

I'm tempted to solder the cap right off the side of the 16F877.


IMHO you're better off using the LABX1 instead of a breadboard. That ICS502 clock generator will give you a nice logic-level output.
For the 18F4550 I'd set the CONFIG to use external clock mode, not xtal (EC, ECIO or ECPLL)
Yeah, but this was just to see if the IC had a heartbeat.


The PK4 can take a while to switch chips, and it's not great with some of those really old devices.
Thing is, the PK4 took forever even if I was programming them sequentially in batch mode; keeping the 18F4550 separate.


It's even been known to blow them up from time to time (the VPP generator can overshoot > 20V)
You see, now that is very worrisome. Gonna go google voltage limiting. I remember seeing voltage clamps last time I was "electronically active".

I just don't know to what limit I should set the clamp for. I suppose the datasheet will give me some indication in "maximum specs".

Robert