As the receiver to control from a central processing unit (CPU) to force that will read the data or send data out of the central processing unit (CPU) by the external system to respond to the signal.
The bus control signals from the central processing unit (CPU) to force it to read data. Or to send off The central processing unit (CPU) by an external system to respond to signals that control.
A bus receiver control from the central processing unit (CPU) to force to read data, or to send the output to the central processing unit. (CPU) by the external system responds to the control signals.