Timer Hardware - Synchronization

There are several situations where timer hardware needs to be in sync with externel timer source. For example, consider the timing for transmitting packets in industrial Ethernet: an EtherCAT master on INtime would keep the tick rate of INtime‘s system timer in sync with the DC clock master.

The timer hardware’s reload register can be used to synchronize the system timer ticks – both in terms of drift and absolute start time - to an external source. You may implement a “software PLL” to lock the interrupts generated by the timer hardware – that make up the system timer ticks - to the external source. The accuracy of this lock is ruled by the high frequency clock signal driving the timer hardware.

Note: Timer hardware synchronization is not the same as synchronizing the INtime wall clock (system time aka time of day) with an external source. In that case the time of day provided by the system is kept in sync with an external source, irrespective of the local system timer characteristics.