Kai said:



We have a chip tester here. I wrote test vectors for the 82C55 which exercise all of the modes. I then used timing strobes to measure the through chip propagation times. I also connected a PMU to the pins to measure the DC characteristics.

The test vectors also allow me to determine the exact nature of the internal logic. For example, I can wiggle a port pin during a read, and see the data bus wiggle, which shows that data is not latched during the read operation.