| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To correctly measure the cycle of an external signal even when a timer clock and a CPU clock are asynchronously operating. <P>SOLUTION: A timer circuit 200 is provided with: a timer 201 for counting the generation interval of an external signal synchronously with a timer clock; a timer register 202 for capturing the counted value of the timer counter 201 synchronously with the timer clock; and a timer register 203 for capturing the value of the timer register 202 synchronously with the CPU clock. The counted value of the timer counter 201 is reloaded into the timer register 202 synchronously with the timer clock based on the external signal, and the second reloading of the value of the timer register 202 into the timer register 203 is performed synchronously with the CPU clock. When the next external signal is generated in the period since the first external signal is generated until the contents of the timer register 203 are read by the CPU, the second reloading is held, and after the contents of the timer register 203 are read by the CPU, the second reloading is performed. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
