Browse Prior Art Database

Open Line Detection on CPU Channel Bus

IP.com Disclosure Number: IPCOM000047074D
Original Publication Date: 1983-Sep-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Bersac, JM: AUTHOR [+2]

Abstract

The circuit shown in Fig. 2, allows the signal on the output line driver to be detected when the load line is not present due to a defective contact, broken wire, or open line. The central processing unit (CPU) is attached to devices 1 to n through a bus, each line of the bus being driven in each device by a driving circuit D. Two lines are shown in Fig. 1. The driving circuit D (Fig. 2) operates as follows: 1 - Operation with load: When input data IN is positive, the output loaded by load resistor RL is positive and the data ECHO is positive. When input data IN is grounded, the level of the data ECHO is 0 volts. 2 - Operation without load: When the input is positive, the output is at a positive level, and when the input is grounded, the output is always also at a positive level.

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Open Line Detection on CPU Channel Bus

The circuit shown in Fig. 2, allows the signal on the output line driver to be detected when the load line is not present due to a defective contact, broken wire, or open line. The central processing unit (CPU) is attached to devices 1 to n through a bus, each line of the bus being driven in each device by a driving circuit D. Two lines are shown in Fig. 1. The driving circuit D (Fig. 2) operates as follows: 1 - Operation with load: When input data IN is positive, the output loaded by load resistor RL is positive and the data ECHO is positive. When input data IN is grounded, the level of the data ECHO is 0 volts. 2 - Operation without load: When the input is positive, the output is at a positive level, and when the input is grounded, the output is always also at a positive level. Since there is a large number of connections between the host CPU and the devices, the probability that contacts are defective in the socket is high. All connections along the bus are checked continuously in order to generate a diagnostic message indicating the wire where a defective contact exists. This is done by analyzing the ECHO outputs of the driving circuits.

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