Abstract: 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.

Abstract: 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.

Abstract: 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.