"StartTimeNextLatch"

Fig.140: EL5031-0011 – StartTimeNextLatch (default)

The 64-bit wide process data "StartTimeNextLatch" (PDO assignment 0x1A01) is enabled by default. In each process data cycle, it specifies the time at which the next SYNC0 pulse and thus the next block of sample values begins (see "Process data timestamp").
"StartTimeNextLatch" therefore changes in each cycle by the amount of the task cycle time with which this terminal is operated.

This time specification is based on the local distributed clocks time of the terminal.
The EL5031-0011 only maps the 64-bit distributed clocks time.
This time specification enables all samples to be linked in time with other time specifications in the EtherCAT bus using the known oversampling factor (see "SYNC0 interrupt")

Example:

In the cycle under consideration, the terminal supplies
in the "DC Oversampling 20 Compact" operation mode with an
oversampling factor n = 20 at
a cycle time T_SYNC0= 1 ms (= 1,000,000 ns)

• as process data a timestamp "StartTimeNextLatch" = 503,330,625,067,077,000_dec and
• 20 measured values position [0]...position [19] of 32 bits each.

The time of measurement of the 5th delivered position value is to be determined, i.e. at which distributed clocks time the 5th position value was determined.

• The currently delivered set of 20 position values was started at the time:
  503,330,625,067,077,000 - 1,000,000 (cycle time) = 503,330,625,066,077,000 ns.
• The time interval between the samples is 1,000,000 / 20 = 50,000 ns.

The 5th position value was thus determined at the time
503,330,625,066,077,000 + ((5 - 1) * 50,000) = 503,330,625,066,027,000 ns.

Special oversampling factor and Shift Time for the SYNC0 pulse