Browse Prior Art Database

Identification of Five Connector States Using Two Pins

IP.com Disclosure Number: IPCOM000036073D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Hayes, IE: AUTHOR

Abstract

An X25 Interface equipment has three network interface cables, one wrap plug, with the possibility of none of these being connected. All five of these conditions have to be detected using just two pins on the connector.

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Identification of Five Connector States Using Two Pins

An X25 Interface equipment has three network interface cables, one wrap plug, with the possibility of none of these being connected. All five of these conditions have to be detected using just two pins on the connector.

An adapter card is designed to drive an X25 network via one of three network interfaces. All three interfaces are driven through a single connector on the adapter, and different cables pick up the correct signals. It is normally only possible to detect four logical states with two bits (00, 01, 10, 11). This design allows the addition of another fifth state. The adapter card makes use of a ZILOG* Z8036 counter/timer and parallel I/O device (CI0) which has two bit-wise bidirectional ports normally used for network control line generation. Two bits on one port are used as identification bits. These bits are taken directly to two pins on the connector, and are tied to +5 V by two 6.8 k resistors (see the figure).

Four states can be sensed directly, by reading the inputs to the CI0 as follows: 1. Pin 1 tied to ground, pin 2 unconnected (pulled high) 2. Pin 2 tied to ground, pin 1 unconnected 3. Pin 1 and pin 2 tied to ground 4. Pin 1 and pin 2 unconnected

These give logic states 01, 10, 00 and ll. On the adapter, these states are used to detect the three network interfaces and the unconnected state.

To detect the wrap plug, another 'state' is required and the bidirectional nature of the CI0 can be...