[CESG] CCSDS 301.0-B-4 propsed pink sheet (Time Code B) / Backward compatibility?

[Gian.Paolo.Calzolari at esa.int]

Erik,
        from a purist point of view I think that it would be incorrect 
stating that the change is backward compatible as a former implementation 
would expect to find always the "Decimal fraction of second" and would 
most likely crashes when that field is absent.
Conversely a constant setting to 0 when not used would be fully backward 
compatible.

However it is also true that despite section 3.5.1.2 "ASCII TIME CODE B, 
Year/Day of Year Calendar Variation" defines only one optional field (i.e. 
the time code terminator) section 3.5.1.3 "SUBSETS OF THE COMPLETE TIME 
CODES" basically allows many fields to be optional so I wonder whether it 
would be more correct working on section  3.5.1.3 instead of adding the 
optional field in section  3.5.1.2.
In other words, the part of 3.5.1.3 clause (c) stating that the code "may 
be abbreviated to the span of interest by deleting the unneeded subfields" 
does already allow removing the Decimal fraction of second subfield?

My cent.......

Gian Paolo

PS It looks to me that the sentence "the need to accommodate the upcoming 
century rollover in only 11 years" was somehow wrong in 2010 as it is now  
:o)




From:   "Barkley, Erik J (3970)" <erik.j.barkley at jpl.nasa.gov>
To:     "CESG -- CCSDS-Engineering Steering Group (cesg at mailman.ccsds.org) 
(cesg at mailman.ccsds.org)" <cesg at mailman.ccsds.org>
Date:   22/07/2016 01:44
Subject:        [CESG] CCSDS 301.0-B-4 propsed pink sheet (Time Code B)
Sent by:        "CESG" <cesg-bounces at mailman.ccsds.org>



CESG Colleagues,
 
Attached is the proposed pink sheet for Time Code B which makes the time 
code more suitable for such applications as publishing a standardized 
schedule of services for which mandatory fractional seconds is 
meaningless.  (By the way does anyone know what the original rationale was 
for requiring, at a minimum, 1/10 of second time statements?)  The 
proposed change is the addition of ?(optional)? which is in keeping with 
the method by which optional is designated for the ?Z? character in the 
recommendation.  I believe the ?.? subfield separator disappears of by 
application of 3.5.1.3 clause (c).    If this change is made to Time Code 
B, we likely should apply it to Time Code A. 
 
Best regards,
-Erik
 
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