The clock subsystem is the heart of the TSync Time Code Processor timing architecture. Time is maintained in the card’s hardware and incremented in 5nsec units, while sub-second information is tracked. Time, from seconds through years, is incremented based on the internal 1PPS derived from the selected input reference.
By default, system time is maintained in UTC, but this can be set to TAI, GPS, or a local timescale (with DST rules). Offsets between timescales are maintained on the card to facilitate conversions between the timescales. The offsets can be set by the user or, depending on the references available, may be automatically determined. Users who wish to use a specific timescale must provide the timescale offset from an input reference or by setting it manually.
The clock subsystem can handle several types of time discontinuities, including leap years, leap seconds, DST transitions, and a user-settable discontinuity. Leap years are automatically detected and handled by the system. Leap seconds, if set from the user or received from an input reference, are also handled accordingly. The system can manage DST transitions set by the user when running in a local timescale.