If there's one thing that irks most of us when developing PIC microcontroller software, it's that sinking feeling when you apply power for the first time and the thing just sits there smugly doing (apparently) nothing. In fact, your PIC chip is probably whizzing away inside some loop or other, or resetting itself several thousand times a second. You'll be none the wiser.

One answer to this problem is to use an existing output pin to output a very short duration Debug word (of around 64ms). When the Micro-Probe described here is connected to the target output pin, it "listens" for any valid debug words coming from that pin

The Micro-Probe has a very simple circuit and uses the ever-popular PIC16F84 in its 10MHz version. It is such a simple circuit, in fact, that it does not really warrant a printed circuit board. Consequently, it has been designed onto a piece of stripboard.