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发表于 2010-5-11 07:36:19
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http://www.sxlist.com/techref/piclist/weedfreq/questions.htm
# @spam@padlam at tcp.co.uk asks:
Can anyone explain what the 74hc132 does? My freq meter works if I pump an oscillator into the RTCC pin of the pic, but doesn't if I come in to the 74hc132.
@spam@je at nanosoft.hypermart.net Answers:
The 74hc132 is actually set up as a multiplexer, so it can read either new count data or the output pulses from RA2. To understand why this is done, one must remember that the prescaler of the TMR0 in the PIC is not readable. Now, being able to feed it pulsles means that you can just keep ticking it over until it gives, allowing you to get an extra 8 bits of accuracy. |
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