Abstract: A system for controlling the issuance of a "Sync In" signal by a disk file controller to a control unit to request a byte of data to arrive at the controller at the same predetermined time regardless of the propagation delay of the cables interconnecting the two units. The system includes a circuit arrangement for measuring the actual propagation delay of the interface cable by issuing a "Sync In" signal at a predetermined time and detecting when the return "Sync Out" signal is received. The measured time is converted to a "Sync In" lead time in terms of bits and bytes. This value is stored and subsequently controls circuitry for issuing the "Sync In" pulse at a bit time which provides the exact lead time necessary for the "Sync Out" signal to arrive at the predetermined bit and byte time so that the data byte will be encoded and recorded at the predefined location on the moving magnetic disk.

Abstract: A control system for a serial data channel for a disk file is disclosed in which a microcontroller is used as the control means. The microcontroller has an input port and an output port, while the serial data channel has a data register. The connections of the data register to the input and output port and the parallel by bit input and output busses on which write data and read data is sent provides a plurality of different data transfer loops through the data register which can be selected under the control of the microcontroller. The arrangement permits functions to be achieved by the microcontroller that heretofore were performed by another device connected to the controller or by special hardware.