CSE2300W
Homework 4
1. (10 points) Assuming 74HCT283’s are used, find the critical path of the circuit in
Figure 6-89 (on page 482). What’s the delay on the critical path? Table 6-3 on page 367
lists the propagation delay of many chips, including 74HCT283. The implementation of
74x283 is shown in Figure 6-87 on page 480.
2. (20 points) Show how to build each of the following single- or multiple- output logic
functions using one or more 74x138 or 74x139 binary decoders and NAND gates. (Hint:
Look at the implementation of a decoder and think about how it is related to minterms.)
a) F =
Σ
A,B,C
(1, 3, 4, 5, 7)
b) F =
Σ
A,B,C,D
(0, 2, 8, 12, 14)
c) F =
Σ
A,B,C,D
(2, 3, 4, 5, 8, 10, 12, 14)
d) F =
Σ
A,B,C
(0, 2, 4, 5)
and G =
Σ
A,B,C
(1, 2, 4, 6)
3. (5 points) Implement F = X
′
•
Z + X
•
Y with the following types of three-state buffer
and a pull-up resistor (if you think it is necessary). Use no more than four three-state
buffers.
4. (10 points) Suppose that you are asked to design a new component, a decimal decoder