Serial I/O channel having independent and asynchronous facilities with sequence recognition, frame recognition, and frame receiving mechanism for receiving control and user defined data

摘要

An Input/Output (I/O) subsystem is provided for transferring frames containing frame control data from a serial data transfer medium to a parallel storage medium. The subsystem includes independent components for processing different portions of the received character stream. The subsystem includes a sequence recognition mechanism for receiving and identifying any of a plurality of digital data bit sequences. The sequences represent channel status information from the data transfer medium. The sequence recognition mechanism provides an interrupt signal derived from the sequences. A frame recognition mechanism responds to the interrupt signal. The frame recognition mechanism receives and identifies a start-of-frame delimiter or an end-of-frame delimiter from the data transfer medium. The frame recognition mechanism provides a frame status signal. A frame receiving mechanism responds to the frame status signal. The frame receiving mechanism receives and identifies a frame header from the data transfer medium. The frame receiving mechanism also verifies link and device level I/O protocol compliance asynchronously while any user defined data included in the frame are being received. The frame receiving mechanism also stores the user defined data in the parallel storage medium concurrently with the verification, if any user defined data are included.