[time-nuts] TIC232 Detailed Operation

Richard H McCorkle mccorkle at ptialaska.net
Sun Aug 13 20:46:18 EDT 2006


The key is the total number of samples added together. Adding
together 5 groups of 125 measurements each works as well as
taking 625 measurements and gives 100ps LSB resolution.
Averaging 5 groups of 125 measurements is the same as 125
measurements and gives an average with 0.5ns LSB resolution

Enjoy!
Richard

----- Original Message ----- 
From: "Glenn" <glenn at net127.com>
To: "Richard H McCorkle" <mccorkle at ptialaska.net>; "Discussion of precise
time and frequency measurement" <time-nuts at febo.com>
Sent: Sunday, August 13, 2006 10:58 AM
Subject: Re: [time-nuts] TIC232 Detailed Operation


>
> 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.
> >
> >




More information about the time-nuts mailing list