Importance

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Abstract

A combined hardware/firmware device and method for automatic recovery of an integrated circuit avoids a disruptive power-on reset after occurrence of an electrostatic discharge which may occur during normal operations or during electromagnetic compatibility testing. The device is incorporated into the chip of the IC and includes an electromagnetic discharge sensor, a flag, and firmware to execute the recovery and reset procedures. The sensor is located between the VDD and VSS lines of the IC which itself includes one or both of a microprocessor and a microcontroller. In a power-on reset sequence, the sensor output and the flag are both set to logic 0. After an electrical transient voltage occurs, the sensor output is set to logic 1. The logic 1 output of the sensor sets the flag, which may be a D flip-flop, to a value of logic 1. When either a power-on reset operation begins or the sensor output is set to logic 1 due to an electrical transient voltage on the VDD-VSS lines, firmware begins a reset subroutine in which (1) the sensor output is reset to logic 0, (2) the status of the flag is checked, (3) if the flag is at logic 1, the firmware performs a recovery procedure to restore predetermined functions of the IC and resets the flag to logic 0 (the recovery procedure being performed on the order of nanoseconds), and (4) if the flag is at logic 0, a general reset procedure is performed. The reset procedure includes a first set of operations and the recovery procedure includes a second set of operations which is different from the first set of operations (for example, a subset or overlapping set). The reset procedure will be disruptive to a user, whereas the recovery procedure involves smooth restoration not noticeable to the user. The apparatus and method permit higher levels of electrostatic discharge to be absorbed by a device without causing permanent damage and/or corrupted data. One particular embodiment for the present invention is for personal computer keyboard microcontrollers.

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First Claim