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Enhanced Microprocessor Monitor With Reset Inhibit And Forced Reset Controls

IP.com Disclosure Number: IPCOM000062765D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Langer, PL: AUTHOR [+3]

Abstract

This article describes a microprocessor monitor with reset inhibit and forced reset controls which prevent loss of microprocessor ability to properly execute c

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 82% of the total text.

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Enhanced Microprocessor Monitor With Reset Inhibit And Forced Reset Controls

This article describes a microprocessor monitor with reset inhibit and forced reset controls which prevent loss of microprocessor ability to properly execute c

The circuit arrangement is shown in the drawing. It has an inhibit input labeled "Watch Dog Timer Inhibit". If this line is held at logic 0, the input pin 2 of U3 is also low. This causes the output pin 3 of U3 to remain high independently of reset signals appearing at pin 1 of U3. Resistor R3 is used for pull up. Resistor R4 is used for transient protection.

The circuit also provides a reset signal to a microprocessor and/or other devices under either one of two conditions as follows: 1) A reset is applied if the line labeled "External Reset Input" is held low. Under this condition, pin 2 of U2 is at logic 0 causing the output pin 3 of U2 and pin 1 of U3 to go to logic 1 regardless of the state of pin 1 of U2. With pin 1 of U3 at logic 1 the output pin 3 of U3 will go to logic 0 if reset inhibit is not applied at pin 2 of U3. 2) A reset is also applied if pin 1 of U2 is held at logic 0 provided the inhibit is not applied at pin 2 of U3. The combination of U2, resistor R1, and capacitor C2 form an astable multivibrator which toggles, thereby providing reset pulses. The combination of capacitor C1, resistor R2, U1, and diode CR2 form a function element which keeps capacitor C2 charged if toggling input appears at capacitor C1 there...