Microcomputer including circuitry for detecting an unauthorized stoppage of the system clock signal
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United States of America Patent
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Aug 12, 2003
Grant Date -
N/A
app pub date -
May 11, 2000
filing date -
Nov 17, 1999
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A microcomputer comprises a selecting unit for selecting one of a plurality of clock signals generated by a plurality of clock generating sources according to a selection instruction from a central processing unit or CPU, a clock generation stop unit, responsive to a stop instruction to stop generation of a clock signal other than the selected clock signal from the CPU, for causing a corresponding clock generating source to stop the generation of the clock signal, and an unauthorized stop process detecting unit, responsive to a stop instruction to stop the generation of the selected clock signal from the CPU, for determining that the CPU has provided an instruction to perform an unauthorized process of causing a selected clock generating source to stop the generation of the selected clock signal. When the unauthorized stop process detecting unit determines that the CPU has provided an instruction to perform an unauthorized process of causing a selected clock generating source to stop the generation of the selected clock signal, it can furnish an interruption signal to the CPU.
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