The control bus is used to carry the control signal b/w the CPU and the peripheral devices connected to it. The control signal are generated by the timing and control units as per the instruction in the instruction register and in reference to the clock signal. These signal tell to peripheral devices, what to do.
The control signal are of two types.
Memory and I/O control signal.
CPU and bus control signal. A few of them are listed below.
Memory I/O control signal.
CPU and bus control signals.