Excavating
Patent
1985-07-11
1987-07-28
Fleming, Michael R.
Excavating
371 66, 371 62, G06F 1100
Patent
active
046835687
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE TECHNOLOGY
The invention relates generally to a method for monitoring computer elements, particularly microprocessors, and more particularly to improving processor efficiency by distinguishing between interrupts and power failures using a single input pin of the chip.
BACKGROUND:
From German Patent Disclosure Documents DE-OS No. 28 42 892 and DE-OS No. 29 03 638, monitoring devices for program controlled equipment are known which recognize short duration disturbances or system breakdowns and thereupon actuate a reset or interrupt input of a microprocessor. This stops the then-running program, which by resetting is put back into proper operation at the beginning of the program, so that an emergency circuit arrangement can be actuated. In such an arrangement, it is a problem that it is impossible to distinguish whether a reset has been brought about by the monitoring device (so-called "watchdog reset") or by other causes, for instance by switching on the supply voltage (so-called "power-on-reset").
In order to attain a definite status after switching on the supply voltage, from which status a normal program course can be started, the emergency circuit arrangement must first be connected to the microprocessor after a stable microprocessor state has been attained. Because of circuitry or program controlled provisions, it is necessary for the connection of the monitoring device to take place in such a way that a reset signal of the monitoring device will not immediately stop the microprocessor and start it up again.
From German Patent Disclosure Document DE-OS No. 32 40 704, a circuit arrangement for monitoring computer elements is know which, for longer-lasting disturbances, keeps attempting to restart the program of the element by means of reset signals. Here also, the problem exists that it is impossible to distinguish between a reset caused by switching on the power, or by the actuation of a reset key, and a reset brought about by a monitoring device.
THE INVENTION
The method according to the invention for monitoring computer elements, particularly microprocessors, has the advantage over the prior art that by means of a simple program controlled decision at the beginning of the portion of the program that follows resetting, it is possible to recognize whether the reset was triggered unconditionally, or by the activity of a monitoring device. Since this decision is made under program control by the microprocessor, it is readily possible to implement changes or make further decisions in the decision-making process. This has the advantage of shortening the restarting of the program considerably, because a complete reinitializing of the registers and reloading of the user program are no longer necessary. It is also advantageous that a decision according to the method of the invention can be made without requiring any special technical circuitry.
DRAWING
An exemplary embodiment is shown in the drawing and explained in further detail in the ensuing description.
FIG. 1 is a circuit diagram of an apparatus for performing the method; and
FIG. 2 is a signal diagram explaining its operation.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
FIG. 1 shows a microprocessor (MP) 1, a monitoring device (watchdog) 2, a power-on reset circuit (PO) 5, a fixed value memory (ROM) 6 and an erasable memory (RAM) 7.
The microprocessor 1 is connected via a bus at one output 13 to the fixed value memory 6 and the erasable memory 7. One output 11 of the microprocessor 1 is connected to one input 21 of the watchdog 2, the output 22 of which is connected to one input of an OR element 4. A further input of the OR element 4 is connected to one output 51 of the power-on reset circuit 5, and the output of the OR element leads to one input 12 of the microprocessor 1.
Via the output 11, the microprocessor 1 furnishes statistically distributed signals in a definite frequency range to the watchdog 2 in a known manner. If the signal is outside this frequency range or data rate, for instance when operation is stopped, then an end
REFERENCES:
patent: 4263647 (1981-04-01), Merrell
patent: 4287565 (1981-09-01), Haubner et al.
patent: 4410938 (1983-10-01), Higashiyama
patent: 4586179 (1986-04-01), Sizazi
patent: 4594685 (1986-06-01), Owens
Fleming Michael R.
Robert & Bosch GmbH
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