Build a 4-to-1 multiplexer that chooses between four single-bit data inputs based on a 2-bit select signal.
Interface
| Signal | Direction | Width | Description |
|---|---|---|---|
a |
input | 1 | Data input, selected when sel = 0 |
b |
input | 1 | Data input, selected when sel = 1 |
c |
input | 1 | Data input, selected when sel = 2 |
d |
input | 1 | Data input, selected when sel = 3 |
sel |
input | 2 | Select line |
out |
output | 1 | Selected output |
Truth table
| sel | out |
|---|---|
| 00 | a |
| 01 | b |
| 10 | c |
| 11 | d |
Use a case statement inside a combinational always block to implement the selection.