Browse Prior Art Database

High Speed Serial Interface Protocol

IP.com Disclosure Number: IPCOM000122483D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04

Publishing Venue

IBM

Related People

Beer, R: AUTHOR [+5]

Abstract

Described is a novel Communications Interface Protocol which facilitates the transfer of data, commands and status information over a twin wire serial interface.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 16% of the total text.

High Speed Serial Interface Protocol

      Described is a novel Communications Interface Protocol
which facilitates the transfer of data, commands and status
information over a twin wire serial interface.

      There is considerable interest in developing serial
communication interfaces to ease the cabling and packaging problems
associated  with existing parallel interfaces, and to allow the use
of smaller cables and connectors. Replacing a parallel bus with a
serial interface is also a valuable means of reducing VLSI chip I/O
pin counts.

      This article reports on a novel protocol which can be
implemented using standard communication logic blocks.  By utilizing
suitably designed high speed data serialisers and deserialisers, data
rates of several megabytes per second are achievable using existing
logic technologies. Although the protocol was designed with the
particular objective of interfacing a Disk Controller to a Disk File,
its flexibility allows utilization in more widespread applications.

      The  protocol has been designed such that commands, data and
status are transferred over the same connections. The protocol
includes an addressing scheme, and supports the signalling of two
types of interrupts.  The handshaking scheme utilized by the protocol
allows streamed and throttled modes of operation.  Since data
communication over a physical medium exposes the data to corruption,
the protocol includes several features to guard against transmission
errors.
SYSTEM REQUIREMENTS

      The protocol described herein allows for the transfer of
commands, status and data between suitably equipped apparatus. The
protocol supports point-to-point and multidrop communication, as
shown in Figure 1.
  o  Figure 1(A) shows apparatus 1 configured to communicate with
apparatus 2, using a point-to-point connection.
  o  Figure 1(B) shows apparatus 1 configured to communicate with
apparatus 2, 3 and 4 using a multidrop connection.

      In the following discussion of the protocol, it is assumed that
one apparatus is a master and the other is a slave.

      The protocol requires the provision of two connections between
the apparatus.  One connection transfers information from the master
to the slave, the other transfers information from the slave to the
master.  Although frames are sent on both these connections during a
transaction, the protocol operates in  half duplex since data can
only be transferred in one direction at a time.

      The master and slave apparatus both require finite state
machines to implement the protocol. For performance reasons, these
would normally be implemented in hardware. The  master and slave
must also be equipped with encoding and decoding circuits to convert
the data into a form suitable for transmission.

      The ENCODER consists of logic which converts data from the
internal representation used within the apparatus into a serial
format.  The encoder may contain...