Worst case execution time problem

I'm with John. (And coincidentally a large part of my past experience was in designing temperature controllers which Must Not Crash.)

The state-machine (etc) approach means that runtime hardware weirdnesses can be detected and dealt with by design, rather than causing an excluded state. Exactly *how* one deals with them is application-specific, but as John says, if the code ain't running you have no chance.

One final thought: with a state machine, it's easy enough for unstable states to be equipped with time-outs.

Steve

Do CS classes at universities teach state-machine programming?

John

Yes. From 1st year on.

Google up:

"state machine" syllabus CS

You'll find all kinds of CS (not EE or CE) courses for 1st year, 2nd year, 3rd year, 4th year, and beyond. 1st year is usually just a concepts stage, taught along with ideas about Turning machines. Often, the course includes 'finite automata' in the name (obviously.) 2nd year actually has them programming some, possibly for a logic design course if nothing else (yes, logic design is taught as a CS course, not only as an EE or CE course.) 3rd year and 4th year will certainly deal with it in compiler writing courses, for example. And other places.

Jon

So am I actually. I just read an absence of any checking into his 'don't check done bits'.

Robert

Hey, I'm not anywhere near as dumb as I look.

I added the input checking because my customer's programming group (very hip guys, writing in C++) decided that they should have a flag that indicated that their console had lost handshake communications with my temperature controller box. The way they stored the flag was to set the "temperature" variable to +3000.

We had to build a stealth blackbox recorder into our code and save all incoming serial communications commands (all up until the NMR probes burned up, $50K a pop) into a battery-backed circular buffer, and seed them out into the field. Guess what we saw?

John

Turning machines? :-) Are we automating lathes now?

Well, you certainly hadn't shown any evidence of that form of insanity before :) I figured I had to be missing something.

Ouch.

Robert

:) My apologies.

Jon