Sync in-sync out calibration for cable length delays

摘要

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. The system further includes circuitry for detecting the occurrence of numerous types of errors which may occur between "Sync In" and "Sync Out" signals.