Control Signals from Control Bus: A number of the control signals are provided to control unit by the control bus. These signals are issued from outside the CPU. Some of these signals are acknowledgement signals and interrupt signals.
On the foundation of input signals the control unit triggers certain output control signals that in turn are responsible for execution of an instruction. These output control signals are:
Control signals that are needed within the CPU: These control signals cause two kinds of micro-operations viz. for data transfer from one register to another; and for executing an arithmetic, logic and shift operation employing ALU.
Control signals to control bus: These control signals transfer data from or to CPU register to or from memory or I/O interface. These control signals are issued on control bus to trigger a data path on the address / data bus etc.