Unisys Corporation

Kin H Ng

Edward T Cavanagh

Douglas E Morrissey

William E Oldham

Gene T Wieder

Apparatus is provided for transferring user defined data from a parallel storage medium to a serial link driver in an I/O channel subsystem of a processor or I/O device controller. The serial link driver transmits a frame of user defined data over a serial data transfer medium. A data buffer receives and stores user defined data from the parallel storage medium. A control data facility that is distinct from the data buffer forms and transmits control data from the sender of the frame to the recipient of the frame via a path that does not include the data buffer. The control data facility includes respectively different dedicated logic for asynchronously generating each of the following: special character sequences, frame delimiters, headers, and cyclic redundancy checksums. A switching facility receives the user defined data from the data buffer. The switching facility also receives control data from the control data facility. The switching facility provides either the user defined data or the control data to the serial link driver. A data path control mechanism signals the switching facility to alternately provide the control data and the user defined data to the serial link driver, thereby forming frames.

Serial I/O channel having dependent and synchronous sources of control

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.

Serial I/O channel having independent and asynchronous facilities with

Apparatus is provided for use in an Input/Output (I/O) subsystem. The I/O subsystem is coupled to a serial data transfer medium that transmits data from a sender to a recipient. The I/O subsystem processes a frame comprising user defined data and frame control data. The frame is received over the serial data transfer medium. The apparatus includes a mechanism for receiving and validating the frame from the serial data transfer medium. The receiving mechanism transmits the user defined data to a first-in, first-out (FIFO) buffer. A mechanism is provided for forming a block header. The block header comprises control data that are used by the recipient of the user defined data. The block header forming mechanism is distinct from the FIFO buffer. A switching mechanism is coupled to receive the block header and a subset of the user defined data. The recipient has a parallel storage medium. The switching mechanism transmits either the block header or the subset of the user defined data to the parallel storage medium. A control mechanism provides signals to configure the switching mechanism to alternately transmit the block header and the subset of the user defined data to the parallel storage medium. By alternating the block header and data, a data block is formed having a size that equals the native sector size of the recipient.

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Glenmoore, PA, United States of America

Kin H Ng