CSC 311 Practice Problem Set #2
- There is an automatic door that opens when someone steps onto the mat with the weight sensor. However, the door will not open if the door is locked. Neither will the door open if there is an obstacle just inside the door (door might hit the obstacle). If the door is unlocked, however, the manager has a remote that can force the door to open even if there is an obstacle just inside. Your task is to design a circuit that takes the four inputs (lock sensor, obstacle sensor, weight sensor, manager remote signal) and produces the output to open the door. Also provide the corresponding Boolean expression.
- Draw a two-bit demultiplexer. This has one data input line, four output
lines, and two control signals.
- Construct a 16-bit comparator using multiple 4-bit comparators (see the circuit notes).
- Consider the shifter in the circuit notes. Given the input number 00110101 for D0 through D7,
(a) what output is produced when C is 1?
(b) and what if C is 0?
- Consider the 1-bit ALU in the circuit notes. If all the gates have a propagation delay of 1 nanosecond and all other delays could be ignored, what is the earliest time this circuit can be guaranteed to have a valid output bit? Think in terms of worst-case delay.
Solutions to these are posted here.