"RogerN" fired this volley in
m:

I guess the point I'm trying to get at is that in machine control you
can write a bad programs that use multi-tasking, that has a thousand
threads each holding up execution until the programmed event. Or you
can have a single loop that is written to detect the conditions you
are looking for to process the program. The only time I need
interrupts is to do something like serial communication or track an
encoder position. Seems like the more modern technology I see, the
more I'm amazed with the Commodore 64.

Your point is well taken, and anyone experienced in low-level programming
( say interrupt-driven M/L) would be easily able to do what you
prescribe.

You may easily be able to do that in an Arduino programming environment
(in which I presently have insufficient experience), but it's not always
possible in commercially-available PLCs. This conversation was taking
the tack about how you can do things like that with a PLC.

I am from the old-school M/L situation, where I not only wrote the
application, but usually wrote the underlying OS and designed the
hardware. In that scenario, it is "easy" to do simultaneous control of
numerous processes. Just get out the assembler, and DO it!

LLoyd