[time-nuts] Fwd: M12+T ASCII interface - I'm confused?
Chuck Harris
cfharris at erols.com
Thu Nov 20 15:33:46 UTC 2008
Stephan Sandenbergh wrote:
> Hi,
>
> Now I'm slightly confused:
>
>>> My gut tells me that <Checksum><cr><lf><@><@> would be believable more than
>>> say 95% (if not 99%) of the time. I've got the following observations:
>
> In the above I assumed no data length checking is employed.
>
>>> - 95% is a bad number in accurate timing applications.
>> You misunderstand. You can get as close to 100% as you
>> want. Some of us have logged data from M12+ receivers without
>> error for weeks or months -- gigabytes, error-free.
>
> Sure, I assume you refer to the case when you check the data length as
> well? I meant that the <Checksum><cr><lf><@><@> byte string could also
> potentially exist in the data itself, but only in very rare cases
> (from there the 95% thumb suck).
No it cannot. It would be:<checksum><cr><cr><lf><lf><@><@><@><@>...
As I understand it, they use a byte stuff code, where any of the "special"
bytes must be doubled if they are in the data.... And, there must be a
data area length check or you could get into some truly pathological situations.
-Chuck Harris
More information about the Time-nuts_lists.febo.com
mailing list