Microcomputer with watchdog timer generating internal and external reset signals
AssigneeOki Electric Industry Co., Ltd.
InventorKazumasa Ozawa
Life of this patent
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Abstract
A microcomputer or microcontroller with a watchdog timer-counter also has an external reset signal generator. When the central processing unit of the microcomputer or microcontroller fails to execute its control program correctly, the watchdog timer-counter generates an internal reset signal for a first interval, resetting the central processing unit, and the external reset signal generator generates an external reset signal for a second interval, different from the first interval. The length of the second interval can be set to match the requirements of external peripheral devices to which the external reset signal is supplied.
Claims18
A microcomputer comprising:
- a central processing unit (CPU) that, when operating normally, repeatedly generates a clear signal;
- a watchdog timer-counter that receives the clear signal from the CPU and, if no clear signal is received for a predetermined length of time, asserts an overflow reset signal for a first interval, thereby resetting the CPU;
- an external reset signal generator coupled to the watchdog timer-counter, for asserting an external reset signal responsive to assertion of the overflow reset signal, the external reset signal being asserted for a second interval differing from the first interval;
- and
- a reset output terminal for external output of the external reset signal.
Dependencies are inferred from the claim text.