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MANUFACTURING TESTING

by George Martin

Start ı The Problem ı A Possible Solution ı Test Setup ı POP Quiz ı Final Exam ı Sources and PDF

Iım trying to concentrate on writing this article in the wake of the attacks on New York and Washington. I wanted to say something about the events but canıt seem to find the words. Hopefully by the time you read this some sort of normalcy will be restored.

If youıre doing a design with one of the current crop of embedded microprocessors, you are likely to be using a background debug module (BDM) pod for development. The newer processors are so compact and complicated that they no longer work with the classic emulators. The old-school emulators used hand-picked (the fastest) versions of the processors with special bonding options. This permitted the various busses to be monitored and, when data patterns were found, break points could be enforced. Needless to say, these emulators were and are quite expensive. On the other hand, the BDM units work with logic built into each micro. This logic can perform the break point and single step functions that are needed to have a useful emulator.

All of this is good news. It means that instead of $30,000 for an emulator, you only need to spend perhaps $500 to $5000. The supporting software also has advanced, so you can single step in your high-level language and view all of your data, including local and global variables. You can even peer into all of your data structures. This is a great advancement.

One of the features that was lost by going to the BDM pods was the ability to map memory in either the debug hardware or the user hardware. I have no idea how you would perform this mapping using a BDM pod. This means you need working hardware in order to get the debugger working. A catch-22 perhaps? Well, itıs not so bad because all you need to get the micro running is power and clock. And, many of these micros have built-in RAM, so some code can be run as the new hardware is brought up and running.

If youıre building large quantities of boards, a manufacturing-defects test fixture and test set is easily justified. However, if you build in lots of 25 or 100 then justifying that investment would be extremely difficult. This is exactly the situation I find myself in this month.

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