问题：
What is the accuracy of the 40MHz internal timebase of the KPCI-3140 board?
答案：
What is the accuracy of the 40MHz internal timebase of the KPCI-3140 board?
The 40 MHz crystal we use is spec'd at +/- .01% which implies it can range in frequency from:
Freq1 = 40,000,000 + (.0001)*(40,000,000) = 40,004,000 Hz
Freq2 = 40,000,000 - (.0001)*(40,000,000) = 39,996,000 Hz
Note: these results take into account temperature, aging, etc. and we typically find the crystals are accurate to .005% (i.e. 2 times better than they are spec'd). The maximum frequency that can be generated by one of our counter/timers which is driven from this crystal is found by taking half the crystal's max frequency...so in this case we would get:
Freq1 / 2 = 20,002,000
Freq2 / 2 = 19,998,000
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