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Appendix| EtherCAT
optoNCDT 2300
In order to ensure that no samples will disappear, due to the high asymmetry between master cycle and slave cycle, the master cycle
time is subject to be less than the time which is required for the generation of a block consisting of x samples.
A complete block is generated from the stated samples and first presented to the EtherCAT side after all stated samples have been
written into the block. If the time for the writing into the block is shorter than the master cycle time, unfortunately single blocks cannot
be transmitted. Reason: The next block has already been filled with samples even before the next block has been picked up by the
master cycle.
Block
10 samples at a distance 100 µs = 1 msMaster cycle > 1 ms
not transmitted blocks
Time for n samples < master cycle time
10 samples = 1 ms
If the number of samples selected is to high, i.e. the time for the filling of a block is longer than the master cycle time, each block is
picked up by a master cycle. However, single blocks and therefore samples are transmitted twice or even more often. This can be
detected on the master side by the transmission of the Timestamp or Valuecounter, see object 0x21B0.
Block
12 samples at a distance 100 µs = 1.2 msMaster cycle > 1 ms
samples > master cycle time
10 samples = 1.2 ms
double (multiple) transmitted blocks
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