Lab one questions and answers

In question 1b, when it says "using a minimal number of NAND gates", this means only use NAND gates.

Q: Are truth tables enough for the explanation of the operation of each of the two latches in part 2a?

A: Not quite; do explain it somewhat tersely. There's no need to go through ALL of the possibilities, but do explain the basic idea.

All of the lab questions of the kind to be answered in sentences (rather than with tables or circuitry) are intended to be answered briefly.

Q: Won't it take a long time to check all of the possibilities in part 1?

A: No! You should be able to go through them all in about eight seconds (like about a second per line), after some practice. That is to say, you would be able to do it in about one second per input combination if you had to do it again in lab 2. If you did it more than a few times, you'd get even faster.

It goes something like this:

• Set all switches to zero
  • Check that the output LED is lit or not lit, appropriately, while you put C to 1 and back to 0 (i.e. you are checking both the 000 and 001 inputs).
  • Set the 'B' switch to one
    • Check that the output LED is lit or not lit, appropriately, while you put C to 1 and back to 0 (i.e. you are checking both the 010 and 011 inputs).
  • You've now checked the first half of the chart.
• Set the 'A' switch to 1 and all other switches to zero.
  • Repeat the previous half.

My answer for question 2b is available in a separate web page. Please don't look at that page until you've thought about this issue yourself first!