CSC270 Homework 4 2011

--D. Thiebaut 10:42, 19 February 2011 (EST)

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This assignment is about multiplexers and RS flipflops. You can work on this assignment in pairs if you wish. The due date is next Friday, at midnight.

Problem #1

• Implement a majority voter with a 4-to-1 multiplexer.
• Show the Karnaugh map and logic diagram that you use to find your answer.
• Similarly, use an 8-to-1 multipler and implement the same majority voter.
• Similarly, use a 16-to-1 mux and implement the same majority voter.

Problem #2

• We saw earlier that we can easily verify a design/circuit by generating its truth table with a Python program.
• How would we represent a 3-to-8 decoder circuit in Python?
• How about a 4-to-1 multiplexer (mux)?
• Prove that your two solutions for Problem 1 are correct by coding them in Python. Include the code and the output of the Python answer in your homework.

Problem #3

• The SR flipflop is the basic element of sequencial circuit. Its main property is memory. It can be used to remember a bit, either 0, or 1. Storing a bit in the flipflop is performed by activating one of the two inputs. Being able to store only a 0 or only a 1 doesn't satisfy the true definition of a bit.

• If we were to switch one of the NANDs in the circuit above for a NOR, would we still have a flipflop? Why or why not?
• If we were to replace both NANDs by two exclusive-ORs, would we still have a flipflop, i.e. a circuit that has memory, in which we can store either 1 or 0?

Submission

• Write your answers in a pdf called hw4.pdf and submit it to your 270b-xx account as usual.