Everybody should have the means to test the hardware he routinely uses to verify that it does what it did yesterday, and what it is supposed to do.

For DIL-40 and PLCC-44 parts, I have a circuit that puts these devices in 8032 mode by grounding nEA, and having them run a checkout program from external ROM that exercises all the instructions and internal memory, as well as lighting up and shutting off LED's connected to all the port pins not involved in the external bus interface. With QFP and TQFP packages that might not be as easy, as those want to attach directly to a PCB. With a proper test fixture or adapter, it is possible, though.

It's not a perfect way to do things, but it is a confidence-building measure.

"Working properly" can mean many things. However, if it doesn't have a functional UART despite the fact it is supposed to have one, and if its timers, etc, don't work as expected, e.g. generate an enabled interrupt at the proper point in a timing loop, something's probably wrong. If something on an IC doesn't work, the entire IC is rubbish, even if you don't intend to use that memory location or timer. If you get several lots of components with similar fault symptoms, well, you need to switch manufacturers.

Just because it blinks a LED or rings a bell, or even echoes a given string to a display of some sort, doesn't mean that it's working correctly. It just means that it's doing something.

RE