Browse Prior Art Database

Hand Shaking Across Switch Matrix

IP.com Disclosure Number: IPCOM000101528D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Harper, HM: AUTHOR [+4]

Abstract

Limitations on the number of input/output (I/O) pins from one device to another might prevent the implementation of needed control signals between devices. In this case more information can be conveyed by encoding the control information within the existing interface bits. If, however, the interface is limited to data transmission only, the problem of implementing needed control signals becomes more evident. A means is provided for incorporating control information within the data stream of an interface where no control path exists.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 55% of the total text.

Hand Shaking Across Switch Matrix

       Limitations on the number of input/output (I/O) pins from
one device to another might prevent the implementation of needed
control signals between devices.  In this case more information can
be conveyed by encoding the control information within the existing
interface bits.  If, however, the interface is limited to data
transmission only, the problem of implementing needed control signals
becomes more evident.  A means is provided for incorporating control
information within the data stream of an interface where no control
path exists.

      Digital data is transmitted by means of some encoding standard.
If the encoding standard to be used eliminates some permutations of
the code, and treats these as illegal for data transmission, then the
illegal subset can be used for control signals.

      Utilizing a code which has this property, where information is
coded into 5 bit sub-bytes, the code points 00000, 11111, 01111 and
10000, among others, are designated as illegal for data transmission.
The all-ones (11111) code point indicates to each device that there
is a ready condition and so transmission of data can begin.  An
all-zeros (00000) code point indicates that the device is either not
ready, or if data was already transmitted, that the device is waiting
for data transmission to cease so that it can handle an existing
interrupt.

      A system consisting of two ports with two separate
unidirectional data path...