FSM activity instructors notes

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FSM activity instructors notes
Activity 1 Mealy Machine Button Box A. Using
the Crazy Hat and Candy Machine as a (hidden)
guide, ask the participants to push buttons and
try to figure out what happens. You might go
around the room asking who wants to call out a
button to be pushed. (An assistant can push the
button). The goal should be to get a chocolate
mint, as opposed to the other candies. Change
hats and dispense candies as the diagram
indicates. Challenge them (what will happen if
I now push GBBRG?) to make sure they have
completely understood the behavior of the entire
system. B. After they succeed (perhaps with some
help), ask how they did it. Discuss each way as
a valid approach. There are many ways to
organize information and keep track of behavior.
If somebody used a graph, then focus on that. If
not, ask if anybody used a graph, or whether they
thought about how a graph might be used, and to
use one (somehow) in what follows. C. Do the
fickle fruit exercise from MATHmaniaCS lesson
5. D. Take time to discuss their solutions,
having volunteers draw on the board. E. Show the
fickle fruit solution transparency, and go over
the definitions and standard notation for FSMs
with input/output along each transition. F. Do
the frustrating fruit exercise, and then the
fancy fruit exercise from MATHmaniaCS lesson 5
this time the participants should use the
standard notation. G. Now go back to the button
box, and this time use the Crazy Hat and Candy
Machine 2 rules. This FSM has output at states
(not on transitions), and in fact has output only
at the goal state of obtaining a chocolate
mint. Emphasize the point when it comes up that
there is no output on the transitions. H. Show
the diagram for the first Hat Candy machine 1,
and talk about output on edges, then compare with
the solution for machine 2. I. Show the Output
Variations transparency (and handout) and
discuss the fact that there may be transitions
with or without output, and states with or
without output. Typically, there is only one
type (transitions only Mealy machine, or states
only Moore machine). Point out that a special
type of Moore machine is a recognizer or
acceptor, where some special states accepting
states may be thought of as outputting YES!,
and other states have no output. Instead of
YES!, we simply double-circle the state. The
goal is often to design a recognizer that says
YES only on a specified collection of inputs.
(We will see examples). See if the participants
can guess what the parity machine shown does.
Make sure that all understand before moving
on. J. Finally, point out that sometimes it is OK
not to draw a transition from a state for a given
input. However, it must be made clear WHAT
HAPPENS when that input is received. The default
assumption is that the machine crashes (like
your PC) and has to be rebooted in order to do
anything useful again. However, it is OK to note
that transitions not shown all go to state X,
or all result in no change of state and no
output, etc.
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FSM activity instructors notes p. 2
Activity 2 FSM design A. Pass out the handout
and show the transparency regarding
considerations while designing FSMs. Discuss
each aspect, and point out that initially it can
be confusing, but experience (and lots of
examples) helps. B. Play Stump Mr. FSM. A
design task is proposed (chosen with a point in
mind, by somebody well-familiar with the
material, and the instructor goes through the
design process out loud, explaining every step
(and false step), reasons for choice of states,
etc. C. As another example, the instructor solves
the Airhead 2000 design problem D. Pass out the
group design problems, and have each group work
on one design (two pairs in a group working on
the same problem, or all four working together.
Instructors wander around and offer help. E.
Groups present their tasks and solutions with
discussion. F. Homework problems are passed out,
and assigned. G. After the activities are all
finished, pass out the MATHmaniaCS lesson.