I'm not having much success in finding an 8031 POST (power on self test) online. I'd be especially interested in tests from a microprocessor manufacturer. For example, are there published tests to verify that the 128 bytes of indirect memory are reliable? Are there simple tests for the SFRs? Thanks for your comments. Robert Berkey
The destructive RAM test has discovered problems. 80C52 software that includes the Borer RAM test and a number of other self-test features has been incorporated into some 200,000 production units. The production contractors are not too analytical about why a unit fails, so I don't have exact figues, but it is clear that processor failures are rare. Probably between one in 1,000 and and one in 10,000. The self-test features generally ensure that units with faulty processors do not leave the factory. Only one service return indicating a failure to pass the destructive RAM test has ever been brought to my attention. The software includes other self-test features inlcuding testing SFRs on the lines that you suggest. I am not aware of this test ever detecting a fault. However, I think it is still worth doing as the effects of such faults may be very subtle. Although faults have been rare, it is important the remember that components are changing all the time. Your software may be put into processors made by different companies at different factories and even into processors that have a completely different construction. As fabrication techniques change, failure rates could change suddenly without warning. I feel that all embeded systems should include a power-on RAM and ROM test as a minimum and that a watchdog of some sort is a very good idea. Depending on the application, you might also consider a continuous ROM test and a non-destructive RAM test.