Advanced Digital Circuits ECET 146 Week 12

1
Advanced Digital CircuitsECET 146Week 12

• Professor Iskandar Hack
• ET 221G, 481-5733
• hack_at_ipfw.edu

2
This Weeks Goals

• Assignment of short project without specific
  instructions on completing project.
• Goal of this project is to force the student to
  review all of the previous labs and examples to
  determine a way to solve the design problem.
• This is the last lab prior to the final project,
  so consider this lab a warm up to the final
  project.
• Thus the amount of guidance provided for this lab
  will be minimal.
• The TA and myself will only answer specific
  questions and aid in determining the source of
  errors. But the student is expected to do this
  lab pretty much without guidance.

3
Vending Machine Specification

• You will design the simplest (and probably the
  least practical) vending machine on the planet.
• This Vending machine will only accept quarters
  and dispense only one product, well call it
  ECET-Cola.
• The cost of the product of ECET-Cola is one
  dollar or 4-quarters
• After receiving four quarters the Vending Machine
  will take the dispense signal high for one clock
  cycle
• The Vending Machine will also have a refund mode
  that will take the refund signal high for the
  number of clock cycles that equate to the number
  of quarters entered
• After either vending or dispensing a can of
  ECET-Cola the vending machine will return to the
  idle mode
• The next slide shows a possible bubble graph, but
  there are other solutions

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Vending Machine Bubble Graph
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Report Requirements

• Simulate the machines operation, but you do not
  have to implement in hardware.
• You do not need to demonstrate this project
  only turn in the report.
• Turn in a short or informal lab report. That is
  only the design files and a COMPLETE simulation.
  The simulation should cover the situations that
  both product is vended and several refund
  scenarios.

6
Some Hints

• In state the transition from states S0, S1, S2,
  and S3 to the next state increment the count to
  keep track of the number of quarters to refund if
  the input refund is pressed. Youll need to use
  an array of flip-flops for this, look at the
  earlier example for a counter.
• Take the output Vend high during the SVEND state
  and Low during all others.
• Take the output RETURN high during the SREFUND
  state and Low during all others.
• Decrement count each clock cycle during the state
  SREFUND, and use an IF statement to determine if
  enough quarters have been refunded.