Control Unit Design Questions and Answers

Answer: A

The statement not expected of the clock is It is not applied to all registers.

In a synchronous CPU, the clock pulses are applied to all registers and flip-flops in the system. Whether a register actually changes on a given pulse is decided by its control signals, such as load or increment enable.

The other options describe what the clock does: it changes register states as the control signals require, it synchronises the activities of the system, and it triggers loading of data into registers or transfers between them.

Answer: C

The statement that is not true of a hardwired control unit is that it enables a simpler control unit design.

A hardwired control unit generates control signals with fixed combinational logic. It needs no control memory and is faster, but its design is complex for a large instruction set and any change means redesigning the circuit, so it is inflexible.

A microprogrammed unit stores control words in a control memory, which makes the design systematic and simpler to modify. So options A, B and D are true of hardwired control, and C describes the microprogrammed approach.