Question

A control unit can generate maximum upto 30 control signals. But at a time atmost 3 control signals can be active. The minimum number of bits required to store the signal information in micro-programmed control unit is_______.

Answer 1

For maximum of 3 signals to be active simultaneously, 3 groups should be present in vertical micro-programmed control unit.
Within each group any of 30 signals can be active, hence we should have are all 30 signals in all 3 groups.

$\begin{array}{ccc}\text{group 1}& \text{group 2}& \text{group 3}\end{array}$
30 signals 30 signals 30 signals

In encoded from

$\begin{array}{ccc}\text{5-bits}& \text{5-bits}& \text{5-bits}\end{array}$ $2^5\ge 30$

Total = 5 + 5 + 5 = 15-bits