| Re: modulo reset [message #41844 is a reply to message #41703] |
Tue, 23 November 2004 11:36   |
Ralf Schaa
Messages: 37
Registered: June 2001
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Member |
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James Kuyper wrote:
> Ralf Schaa wrote:
> ...
>
>> I am reading binary data (not longer than 32 bit, and I store it in
>> ULL as suggested)
>> and the 'modulo reset' I talked about may appear at one datafield:
>> that is in an accumulated
>> "Doppler" cycle count.
>> By differentiating with respect to time, one can get the true doppler
>> count.
>
>
> "Differencing", not "Differentiating". You differentiate a continuous
> function of time. For a discontinuously sampled function, you can't
> differentiate, you can only calculate finite differences.
yep, of course
>> Than the documentation says, when a modula reset occurs , add 2^32.
>> I think, this means when the counter is full and is starting with zero
>> again. than add the 2^32.
>> But I don't see what adding 2^32 exactly would do ...
>
>
> Let's assume that the current cycle count is t0=2^32-5. 20 cyles later
> the true count would be 2^32+15. However, because it reset at 2^32, the
> actual number in the cycle count would be t1=15. If you calculate the
> time difference as dt = t1-t2 while storing the value in, for instance,
> a 64 byte integer or floating point type, then the dt will be
> 15-(2^32-5) = 20-2^32. To get the correct number of cycles, you have to
> add in 2^32, leaving you with dt = 20.
sounds good, i'll try that.
thanks
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