EET205 Fall 2015
HOMEWORK 4:
(Due 11/24 via email or hard copy by the start of class;
email me if you have any questions. Some of the questions are subtle.)
Read Kleitz, Chp. 12 (and review Chp. 13). You may want to review chp.10.
- Create a divide-by-ten counter out of flip-flops (you may use J/K, S/R, D, and/or T flip-flops) and any basic logic gates (AND, OR, NAND, NOR, NOT, XOR, XNOR) that you need). Draw the schematic and briefly describe how it works. I recommend using MultiSim or a similar program to draw the schematics (that’s how I draw many of the ones in the lectures and labs), but hand-drawn schematics are fine if you prefer to do that.
You’re welcome to use MultiSim in the Electronics lab,
when the room is available.
- One of the most important concepts in electronics – especially in digital electronics – is modularity. Once a circuit has been designed to do a particular function (like the divide-by-ten circuit above), it can be kept as part of a circuit library, and reused – without having to re-invent it each time.
Using three divide-by-ten “black boxes,” each with a clock input and four outputs (Q3, Q2, Q1, Q0), design a divide-by-1,000 counter. (You don’t need to redraw the schematic from #1 above; just assume that it works and use a “black box” for each instance of it, with the inputs and outputs labeled.
- How many (legal) states does your design from #2 above have? Why?
- Since each flip-flop might power up in either the Set or Reset state,
a counter which uses N flip-flops might power up in any of 2^N possible states. How many total (legal and illegal) states does your design from #2 above have?
- (extra credit, since this is tricky) How many possible states could your design from #2 above be in, after it is powered up in an unknown state and fifty (50) clock cycles have been input? (Hint: after that many cycles, you know the ones’ place counter will be in a legal state. What about the others? What states could they be in?)
Explain your reasoning for full credit.
