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Browse Prior Art Database

Protocol for Switching the Mode of the Bidirectional-Data- Transfer Feature

IP.com Disclosure Number: IPCOM000100102D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 84K

Publishing Venue

IBM

Related People

Fredericks, KJ: AUTHOR [+2]

Abstract

Disclosed is a method to switch to a different mode of the bidirectional-data-transfer feature other than the mode that was established during initial-selection sequence.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Protocol for Switching the Mode of the Bidirectional-Data- Transfer Feature

       Disclosed is a method to switch to a different mode of
the bidirectional-data-transfer feature other than the mode that was
established during initial-selection sequence.

      Reference (1) describes a new feature to the parallel I/O
(OEMI) interface which is defined in reference (2).  The new feature
dynamically identifies whether the parallel I/O (OEMI) interface is
used in the traditional mode or in the bidirectional-data-transfer
mode. Either "normal-interlock mode" or "data-streaming mode" for the
bidirectional-data-transfer feature may be selected at
initial-selection sequence time.

      After the bidirectional-data-transfer feature has been
signalled and accepted by both the channel and the control unit
during the initial-selection sequence, the desired mode of data
transfer to be performed is identified by:
      1.   If the device initiates data transfer by raising the 'data
in' line, then data is transferred using the data-streaming protocol
(data-streaming mode).
      2.   If the device initiates data transfer by raising the
'service in' line, then data is transferred using the normal-
interlock protocol (normal-interlock mode).

      During an I/O operation, a device can switch to one-byte normal
data transfer mode, at any time and for any number of bytes, by using
the 'mark 0' line instead of either 'service in' or 'data in'.  When
the device requests or offers a byte of data one byte at a time, the
transfer is performed using 'bus 0' and the normal-interlock
protocol.  The I/O operation reverts to the mode selected at
initial-selection time whenever the device uses either the 'service
in' line or the 'data in' line.

      During an I/O operation...