[time-nuts] TIC232 Detailed Operation

Glenn glenn at net127.com
Sun Aug 13 14:58:36 EDT 2006


I've never programmed a PIC, nor do I know much about TI measurements.
But, if you wanted 100 ps resolution, would it make sense to average five
125 samples?

thanks,
glenn

Richard H McCorkle wrote:

>By selecting a known sample time for the XO speed used, the LSB 
>of the displayed data has a known time value. By default the 60-second 
>sample period gives an LSB of 1.04ns. No dividing by the sample time 
>or other scaling needs to be done to the count displayed, it is already 
>scaled by the XO speed and sample time used. By changing the 
>sample time to calibrate the reading, the count can be scaled to read 
>directly. For instance, accumulating 625 samples with a 16 MHz XO 
>speed would result in a count with an LSB of 100 ps. Since the Simple 
>Time Interval Counter only goes to 256 samples, averaging 250 samples 
>would give an LSB of 0.25ns and an output count displayed once every 
>4:10. An LSB value of exactly 1ns would require 62.5 seconds per 
>update. Because partial sample times aren't allowed, a 60-second 
>value was chosen as default giving an LSB of 1.04ns and an output 
>count displayed once per minute.
>  
>



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