| 摘要 |
<p>PURPOSE:To adjust the accuracy of a clock automatically without being limited by the selection of a crystal oscillator by dividing the output signal of an oscillation device at a correction frequency division ratio by a programmable frequency divider whose frequency division ratio is optionally settable. CONSTITUTION:The programmable frequency divider 14 divides the clock 100 of the input oscillation signal at the frequency division ratio written in a nonvolatile memory 15 and outputs the result as a timer interruption signal 200 to a CPU 13 and an external output terminal 18 and a CPU 13 perform time calculation through software with the signal 200. When the clock accuracy of a timer microcomputer 10 is adjusted, an external adjustment device 6 is connected to external terminals 7 and 8 to input the signal 200 and the correction frequency division ratio N0+DELTAN (N0: center frequency division ratio, DELTAN: deviation from N0) is calculated from the frequency measured value and written in a memory 15. The frequency divider 14 corrects the oscillation frequency division of the crystal oscillator 12 by using the correction frequency division ratio N0+DELTAN to obtain the accurate frequency of the signal 200, thereby securing the clock accuracy of the CPU 13.</p> |
