All,
Two of my kids are competing in this years BEST robotics
design competition. Rules are here, FYI:
http://www.bestinc.org/b_game_rules.php
The competition is to build a robot which will assemble logic
element stand-ins into logic gates and CPU elements (not actual ones,
everything is sylized so that the robots can be made out of easily
available macroscopic materials). However, an important element of
the competition, on which the older child is working, is to write a
"business case" for such a robot - do market research, in essence,
and convince investors why such a device is useful.
When I heard "market research" I immediately thought of this
group as probably the best concentration of knowledge anywhere on why
anyone would want to build custom-configured logic circuits as
opposed to using a generic general-purpose microcontroller for the
same task.
I *think* I know part of the answer. My thoughts are generally:
1) Anything custom-configured to the task at hand can have number of
logic gates, number of transistors, etc. optimized to that task.
Register length can match precision of sensors, etc. Thus, *all else
being equal*[1], minimum resources (power, heat generated, etc.) will
be required by the resulting system.
2) Anything custom-configured can have performance optimized - state
machines or flip-flops (vs. combinatorial logic) implemented only
when necessary, path lengths shortened where possible, etc. to
provide minimum feedback-control times.
3) Anything custom-configured can have minimum complexity. For
mission-critical applications, this means it becomes exponentially
easier to "prove" correct control system functionality and to predict
performance even in the case of SEU or other problems;
general-purpose microcontrollers are much more difficult to validate
in this sense.
I would love comments, and particularly references (places to
look on internet, conference proceedings, etc.) from anybody who
would care to provide them. Replies on the list to the extent you
think they are on-topic, or direct to me and my cc'd daughter if off
topic. Thanks in advance!
[1] I know microcontrollers have the advantage of gate size *far*
below what any discrete components currently can achieve; that's the
caveat I'm trying to leave with the "all else" comment. I assume part
of the business case has to be that a robot assembling logic designs
can be made arbitrarily small so that gate feature size for the
discrete logic can compete with gate feature size for large-scale
IC's.
--
- Mark 210-379-4635
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