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Diagnostic Method for Analog Circuit

IP.com Disclosure Number: IPCOM000035882D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Inui, T: AUTHOR [+4]

Abstract

This article describes a method of adding a simple simulation circuit to diagnose an analog input circuit by microcode. A key problem with diagnostics for analog circuits of computer input devices is that an image scanner provides the instability of analog input signals to an analog-to-digital (A/D) converter. (Image Omitted) Following is the summary of the additional circuit and microcode:

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Diagnostic Method for Analog Circuit

This article describes a method of adding a simple simulation circuit to diagnose an analog input circuit by microcode. A key problem with diagnostics for analog circuits of computer input devices is that an image scanner provides the instability of analog input signals to an analog-to-digital (A/D) converter.

(Image Omitted)

Following is the summary of the additional circuit and microcode:

Hardware inputs a constant voltage signal to the amplifier by disconnecting the interface cable between the input device and the A/D converter.

Microcode verifies the digital data controlled by gain control circuits of the amplifier through the A/D converter.

Fig. 1 shows the image scanner and a scanner adapter card whose analog circuit is diagnosed by this method.

Referring to Fig. 2, the adapter card has circuits which convert the analog video signal to digital signals. The analog video signal is inputted from the image scanner via scanner cable and amplified by the gain control circuits on the adapter card. The amplified analog signal is then converted into digital signals by the A/D converter on the card.

When the cable is connected, the -SCEX signal is at a ground level of the scanner. The microcode in the adapter card checks the level of the -SCEX signal to determine whether or not the cable is connected to the scanner. When the cable is disconnected, the -SCEX and VIDEO signals are opened. In this condition, the input voltage to the...