Abstract: A method for controlling the data transmission of a central unit interfacing control circuit and a circuit arrangement for the implementation of the method. The control of the data transmission between a central unit and a communication controller with the central unit interfacing control circuit is guaranteed under real-time conditions on a part of the central unit channel interface and is guaranteed on a part of the communication controller with a processing speed inherent in the microprocessor unit that controls the central unit interfacing control circuit. The central unit interfacing control circuit has a ROM interface controller that controls all control executions at the central unit channel interface under real-time conditions thereby relieving the microprocessor unit. The microprocessor unit can thereby operate the communication controller interface with its maximum possible processing speed.