Table 62 defines the data objects of LN LTPC (PTP clock). The explanation of DO GmClkAcc is as follows: "Grandmaster clock time accuracy class, according to IEC 61588:2009, 8.2.3.7., expressed in nanoseconds". There are concerns regarding the "expressed in nanoseconds".
DO GmClkAcc corresponds to grandmasterClockQuality.clockAccuracy of IEC 61588:2009 / IEEE 1588:2008, according to Table 79 in clause 19.6.
clockAccuracy is defined as enumeration, according to Table 6 of IEC 61588:2009. For example, the enumeration value hex 29 is specified as "The time is accurate to within 1 ms".
The "expressed in nanoseconds" in the explanation of DO GmClkAcc can be understood as not providing the enumeration value (e.g. hex 29 = dec 41) in GmClkAcc but the corresponding time accuracy value in Table 6, in nanoseconds (e.g. dec 1,000,000 for 1 ms).
This tissue asks for clarification whether this interpretation of the GmClkAcc definition is correct or not.
If the above interpretation is correct then it raises at least the following concerns:
1) How to express the enumeration value hex FE ("Unknown") in nanoseconds ?
2) How to distinguish the enumeration values hex 30 ("... within 10 s") and hex 31 ("... > 10 s") in nanoseconds ?
3) The value of 10 s in nanoseconds (dec 10,000,000,000) exceeds the maximum value of INT32 (dec 2,147,483,647). INT32 is the attribute type of the stVal attribute of INS, which is the common data class of GmClkAcc.
Proposal
DO GmClkAcc should provide the enumeration value of clockAccuracy but not the corresponding time accuracy value in nanoseconds. Remove the "expressed in nanoseconds".
Discussion
Created
Status
Agree with the proposal as well.
15 Sep 25
Triage
Agree with the proposal.
15 Sep 25
Triage
Fully agree. The value in the attribute is a time accuracy class.
Stating specific units in such definitions is a bad practice anyway.