Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Patent
1997-09-17
1999-12-14
Beausoliel, Jr., Robert W.
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
G06F 1100
Patent
active
060031409
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE TECHNOLOGY
The invention concerns a method for monitoring an electric computing unit for which a reset signal is transmitted from a voltage monitoring device to the computing unit, following an initialization of the computing unit, if there is no supply voltage or the supply voltage drops, and for which the operating state of the computing unit is checked following the occurrence of the reset signal by comparing a content of a volatile memory unit with a fixedly predetermined code and a decision is reached concerning the further control sequence. The invention directly relates to an arrangement for monitoring an electronic computing unit having at least one volatile memory unit with a code that is entered during an initialization; having a voltage monitoring device, which can be used to generate a reset signal for the computing unit if a supply voltage from a voltage source is not supplied or drops off; having a comparator unit for determining whether the content present in the volatile memory unit following the reset signal coincides with a predetermined code that corresponds to the entered code; and having a decision unit for emitting signals on the basis of the comparison result.
A method or an arrangement of this type is already known from the EP 0 163 670 B1. With this known method or this known arrangement, a reset signal is triggered for a computing unit if the voltage supply is interrupted or if the computing unit does not emit signals. If the computing unit does not emit signals, an external monitoring device in the form of a so-called watch-dog reset responds, for which a pattern typical for the watch-dog reset history known a-priori is present in at least a small portion of a volatile memory unit of the computing unit. A corresponding pattern from a non-volatile memory unit is loaded in for a comparison. If the values existing in the non-volatile memory unit correspond at least in part to the predetermined pattern, a decision is made that the reset signal comes from the monitoring device. If the values from the non-volatile memory unit do not coincide with the predetermined pattern, then it must be assumed that the reset signal is caused by an interruption in the voltage supply. With a reset signal coming from the monitoring device, a specific program sequence is set in motion, while the computing unit is initialized anew if the reset signal is the result of an interruption in the voltage supply. Such interruptions in the voltage supply, which trigger a reset signal, to be sure, but do not actually cause a malfunction in the computing unit cannot be distinguished clearly with this known device.
ADVANTAGES OF THE INVENTION
It is the object of the invention to provide a method or an arrangement of the aforementioned type, designed to distinguish easily and reliably between interruptions in the voltage supply that result in malfunctions in the computing unit and interruptions in the voltage supply that do not cause malfunctions in the computing unit.
SUMMARY OF THE INVENTION
The above object generally is achieved according to the method of the invention in that the reset signal is always emitted by the voltage monitoring device if the supply voltage drops below a voltage level, above which a defined operation of the computing unit is ensured; that for each reset signal, the content of the volatile memory unit is compared to the predetermined code and that for control purposes, the operating state existing at the time when the reset signal occurs is continued if the content of the volatile memory unit coincides with the code, whereas a new initialization is carried out if the code deviates from the content of the volatile memory unit. For this latter purpose a first signal is emitted by the decision unit if the content of the volatile memory unit deviates from the predetermined code, which signal triggers a re-initialization of the computing unit; and a second signal is emitted if the content coincides with the predetermined code, which results in a continuation of the control se
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Blitzke Henry
Meier Hans
Pientka Rainer
Beausoliel, Jr. Robert W.
Elisca Pierre E.
Kunitz Norman N.
Robert & Bosch GmbH
Spencer George H.
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