Objectives
We will learn how to design and build state machine circuits.
Part 1. A complex counter
- There is an input X to the 3-bit counter.
- If X = 0, the counter will count from 0-1-2-3-4-5-6-7 and repeats
- If X = 1, the counter will be a gray-code counter.
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i.
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Design this circuit (Include a MOORE state digram, state table,
and K-maps/algebra to simplifly the circuit.
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ii.
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Build the circuit and simulate is using xilinx.
Be sure to simulate both direction completely and
change input X from 0 to 1 at random time to verify the
counter reacting properly to the input changes.
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Part 2. 15-second time bomb
Design a counter that starts at 15 and count to 0.
There are several input to this circuit:
- [start] : start the counter
- [stop] : stop the counter
- [reset] : reset back to 15 seconds
The output should include:
- [counter index] (in binary is OK)
- [blow_up] indicator when the sequence reaches 0000.
You should use a D-FF that allows your to pre-set value (try FDSRE or similar ones).
Note, figure out which D-FF you want to use & understand how it works before you
connect all the wires together. Once you figure out how FDSRE works, you may need to
add a few logics so that the time bomb does not blow up when you start.
Simulate with start=0 first, then switch start=1.
The counter should be at 1111 & the blow_up indicator should be 0 until the counter
becomes 0000. Also, simulate the case that when start=1 but you realize at 5 second
before blowing up, you need to stop it & reset it back to 15 seconds again.
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i.
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Design this counter (including MOORE state digram, state table, and K-maps, etc)
Note, remember to simplify your design as much as possible.
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ii.
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Build and simulate the circuit using xilinx.
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Part 3. Freeway Traffic Control
Around 4pm in the afternoon when much of the traffic starts to enter the
freeway, a set of GREEN/RED signal are used to prevent highway jams. Here
is how the traffic signal works.
- There will be 2 lanes to enter the freeway: 1 carpool lane and 1
regular lane. Each lane will have a GREE/RED signal.
- When both lanes have cars waiting, each lane will
take turns to go (GREEN will rotate between 2 lanes).
- When both lanes have no cars, both signal will be RED
- When 1 lane has cars, only that lane will be GREEN.
The other lane will always be RED.
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i.
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Design this circuit (Include a MOORE state digram and briefly
describe the state diagram and how it satisfies the requirement
definition. Also include the state table, and K-maps, algebraic
equation, and final schematic).
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ii.
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Build the circuit and simulate is using xilinx
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iii.
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What happens when your car breaks down on the carpool lane at
the signal and it's your turn to go on GREEN light?
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Report
You know the drill by now!
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