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Improvement to Transmit Activity Check for Twinax Work Station Controllers

IP.com Disclosure Number: IPCOM000116767D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Dancker, GA: AUTHOR

Abstract

Changing the way the Transmit Activity Check (TAC) logic works so that twinax Work Station Controllers (WSC) can operate better on marginal cable networks is described. Instead of the WSC aborting a transmission when a TAC error occurs, continue the transmission and allow the attached display or printer to report the error if one occurs.

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Improvement to Transmit Activity Check for Twinax Work Station Controllers

Changing the way the Transmit Activity Check (TAC) logic works so that twinax Work Station Controllers (WSC) can operate better on marginal cable networks is described. Instead of the WSC aborting a transmission when a TAC error occurs, continue the transmission and allow the attached display or printer to report the error if one occurs.

As shown in the Figure, current twinax Work Station Controller (WSC) designs wrap the transmit data back through the receiver and do a bit-by bit-compare during normal operations, as shown in the Figure. The digital (TTL level) data (1) is sent to the twinax Driver/receiver module. The driver (D) converts this to a differential analog signal (2). The analog signal is wrapped back (3) to the receiver
(R) where it is converted to a TTL receive data signal (4). The WSC logic compares receive data (4) to transmit data (1). If there is a miscompare, a Transmit Activity Check (TAC) error is set.

On marginal cable networks, when the WSC logic is transmitting data, the attached cabling (attached to (2) in the figure) can cause reflections and interfere with the signal that the WSC receiver detects. The WSC logic detects this miscompare, aborts the current transmission (by sending a frame with bad parity), and flags an error. However, in many cases, the attached display or printer is able to receive the data correctly, since the reflections on the cable are usually...