Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
1999-01-08
2002-05-07
Ray, Gopal C. (Department: 2181)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C709S241000
Reexamination Certificate
active
06385743
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention lies in the field of microprocessors. More specifically, the invention relates to a monitoring method for testing the operability of a microprocessor, particularly when the microprocessors are run up from a quiescent mode to an operating mode.
The invention relates, in particular, to a method of synchronizing an electronic device for monitoring the operation of a microprocessor (watchdog) with the microprocessor when the microprocessor is being run up from a quiescent mode to an operating mode, whereby
the synchronization includes producing a trigger signal with the microprocessor, transmitting the trigger signal to the monitoring device, and indicating with the trigger signal the operational availability of the microprocessor;
the monitoring device, in order to receive the trigger signals, temporally toggles between a CLOSED window status, in which a trigger signal cannot be detected by the monitoring device, and an OPEN window status, in which the received trigger signal brings about synchronization between the microprocessor and the monitoring device.
The invention also relates to an electronic device for monitoring the operation of a microprocessor (watchdog), having a trigger signal input which toggles, in a clocked manner, between a disabled position (CLOSED window) and an enabled position (OPEN window). The trigger signal is received during the OPEN window in order to bring about synchronization between the microprocessor and the monitoring device.
As indicated in parentheses above, such monitoring devices are referred to as watchdogs. A particular refinement of such watchdogs is so-called window watchdogs which provide time windows that are spaced apart from one another and within which a trigger signal can be received signaling the operational availability of the microprocessor that has been run up, in order to bring about the desired synchronization between the microprocessor and the monitoring device. These time intervals are usually termed OPEN windows. The OPEN windows are separated from one another by so-called CLOSED windows in which trigger signal detection is not possible and the trigger signal input of the monitoring unit is thus disabled. Depending on the desired application, the time periods of the OPEN window and the CLOSED window may be the same or else different. The temporal change sequence of CLOSED window and OPEN window starts with a CLOSED window status.
Synchronization between the microprocessor and the monitoring device is brought about by virtue of the fact that, on achieving operational availability, the microprocessor produces a trigger signal which is applied to a corresponding trigger signal input of the monitoring device. If the monitoring device detects a trigger signal, the synchronization reset is carried out, in which, when the trigger signal is received, the monitoring device immediately closes the OPEN window status and starts toggle operation, starting with a CLOSED window. During this synchronization reset, the clock-signal generator continues to oscillate, so that the time period necessary for synchronization is very short.
With both the microprocessor and the monitoring device initially in a quiescent mode, a wake-up interrupt is produced in the microprocessor whenever there is a signal capable of initiating wake-up present at one of its inputs. The increase in current consumption of the microprocessor when it is running up activates the monitoring device, which adopts its toggle operation between the CLOSED window status and the OPEN window status, starting with a CLOSED window. At the instant at which toggle operation starts, the clock-signal generator of the microprocessor has not yet reached the steady state and is not stable, however. The microprocessor does not achieve operational availability until the clock-signal generator has reached the steady state and is stable. At that instant, the microprocessor produces the trigger signal. The instant is undefined within specific limits. Consequently, the trigger signal may fall in the first CLOSED window, so that this trigger signal does not bring about the desired synchronization reset. A synchronization reset is carried out only if the trigger signal happens to fall in the OPEN window adjoining the CLOSED window. From that instant on, the toggle operation of the monitoring device runs synchronously with the microprocessor.
If the trigger signal does not appear in an OPEN window, provision is made for a full reset of the microprocessor to be triggered at the end of the time period of the first CLOSED and OPEN windows. Although this reset ultimately also leads to synchronization between the microprocessor and the monitoring device, it means that the microprocessor is fully restarted. In the time required for this reset, the microprocessor cannot be used for performing the desired actions. Furthermore, data recorded in available storage elements may be deleted in the course of such a reset. Deleting the stored information is often undesirable, however, particularly when the stored data are position data for an actuator and position detection for the actuator operation is carried out on a relative basis.
Since, from a statistical point of view, there is a very high probability that the trigger signal produced by the microprocessor will fall in the first CLOSED window of toggle operation of the monitoring device, indirectly triggering a full reset of the microprocessor, and hence also renewed stabilization of the clock-signal generator, at the end of the OPEN window which follows this CLOSED window, not only is the current consumption for synchronization undesirably high, but the response time of the microprocessor is also too long.
Other monitoring devices are known, which have trigger signal inputs with a window sequence comprising nothing but OPEN windows. These monitoring devices do not have the problems described above. However, the monitoring function of a window watchdog is improved many times on account of the necessary synchronization described between the microprocessor and the monitoring device.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method of synchronizing a window watchdog with a microprocessor, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which enables both units to be synchronized without running the risk of fully resetting the microprocessor when it is operable. In addition, the invention is based on the object of providing a window watchdog with which synchronization with the microprocessor is correspondingly possible.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of synchronizing a microprocessor watchdog with a microprocessor when the microprocessor is run up from a quiescent mode to an operating mode, which comprises:
producing a trigger signal with a microprocessor indicating an operational availability of the microprocessor, and transmitting the trigger signal to a microprocessor watchdog;
temporally toggling the microprocessor watchdog between a CLOSED window status, during which the trigger signal cannot be detected by the monitoring device, and an OPEN window status, during which the received trigger signal brings about a synchronization between the microprocessor and the microprocessor watchdog; and upon having been activated, providing an OPEN window range over a predetermined time period with the monitoring device, whereby the time period is predetermined to detect the trigger signal produced by the microprocessor operating under normal conditions.
In other words, the invention is characterized by the process in which, after it has been activated, the monitoring device provides an OPEN window range over a predetermined time period, and the time period is designed to detect the trigger signal produced by the microprocessor operating in normal conditions.
In accordance with an added feature of the invention, at the end
Huckfeldt Olaf
Lenz Michael
Greenberg Laurence A.
Infineon - Technologies AG
Lerner Herbert L.
Ray Gopal C.
Stemer Werner H.
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