**Assignment
No. 4 – Combinational Logic Design**

1. Design an excess-3-to-BCD code converter that gives output code 0000 for
all invalid input combinations.

2. Design a circuit to implement the following pair of Boolean equations:

To simplify drawing the schematic, the
circuit is to use a hierarchy based on the factoring shown in the
equation. Three instances (copies) of a
single hierarchical circuit component made up of two AND gates, and OR gate,
and an inverter are to be used. Draw the
logic diagram for the hierarchical component and for the overall circuit
diagram using a symbol for the hierarchical component.

3. By using the combinational circuit analysis technique learned in class,
verify that the circuit shown in Figure 3-32 (4e) or Figure 3-55 (5e) generates
the exclusive-NOR function.

4. The NOR gates in Figure 6-26 (4e) or Figure 2-39 (5e) have propagation
delay

t* _{pd}* = 0.073 ns and the
inverter has a propagation delay t