Issue 5596: change time format in order to make the offset obsolete (smart-transducers-ftf) Source: Institut fuer Technische Informatik (Mr. Thomas Losert, thomas@vmars.tuwien.ac.at) Nature: Uncategorized Issue Severity: Summary: Even the smallest 8-bit microcontrollers should be capable of dealing with signed numbers in the 2-complement representation. Thus the following changes are proposed: In Section 2.3.8 "... plus an offset of 2^38 seconds. The offset is introduced to be able to express instants before January 6, 1980 as positive values." should be replaced by "Instants before January 6, 1980 are represented as negative values." The IDL in Section 3.4 should be changed in the following way: "typedef unsigned long long TimeInstant" should be replaced by "typedef long long TimeInstant" and "typedef unsigned long long TimeDuration" should be changed to "typedef unsigned long long TimeDuration"; in addition the description in Section 3.5 must be changed Resolution: Accept changes as proposed. Revised Text: 9/29/02 Page 15 Changes done as proposed. Section 3.5 contains now the following: long long TimeInstant: This type is used for timestamps. The 40 upper bits represent the number of seconds (all 34841 years an overflow will occur) while the remaining 24 bits represent the fractions of a second, allowing an accuracy of 60 ns. In a system with external clock synchronization the 40 upper bits are initialized with the value 0 at 00:00:00 UTC on January 6, 1980, which is also the reference starting point (the epoch) for GPS-time. In this way every point in time 17420 years before and 17420 years after January 6, 1980 can be uniquely represented with an accuracy window of 60 ns. Stand-alone systems without external clock synchronization are set to 0 during initialization. Smart Transducers FTF Finalization Task Force Report Disposition: Accepted OMG Issue No: 5597 long long TimeDuration: This type is used for durations that are represented in units of 2 -24 seconds (about 60 ns). Actions taken: August 27, 2002: received issue December 11, 2002: closed issue Discussion: End of Annotations:===== Title: change time format in order to make the offset obsolete (smart-transducers-ftf) Source: TTTech Computertechnik AG (Mr. Thomas Losert, thomas@vmars.tuwien.ac.at) Summary: Even the smallest 8-bit microcontrollers should be capable of dealing with signed numbers in the 2-complement representation. Thus the following changes are proposed: In Section 2.3.8 "... plus an offset of 2^38 seconds. The offset is introduced to be able to express instants before January 6, 1980 as positive values." should be replaced by "Instants before January 6, 1980 are represented as negative values." The IDL in Section 3.4 should be changed in the following way: "typedef unsigned long long TimeInstant" should be replaced by "typedef long long TimeInstant" and "typedef unsigned long long TimeDuration" should be changed to "typedef unsigned long long TimeDuration"; in addition the description in Section 3.5 must be changed. Resolution: See above. Revised Text: Changes done as proposed. Section 3.5 contains now the following: long long TimeInstant: This type is used for timestamps. The 40 upper bits represent the number of seconds (all 34841 years an overflow will occur) while the remaining 24 bits represent the fractions of a second, allowing an accuracy of 60 ns. In a system with external clock synchronization the 40 upper bits are initialized with the value 0 at 00:00:00 UTC on January 6, 1980, which is also the reference starting point (the epoch) for GPS-time. In this way every point in time 17420 years before and 17420 years after January 6, 1980 can be uniquely represented with an accuracy window of 60 ns. Stand-alone systems without external clock synchronization are set to 0 during initialization. long long TimeDuration: This type is used for durations that are represented in units of 2 -24 seconds (about 60 ns).