CanOpenSync

CANopen defines something like a "Synchrounous windows length" It is recommended that a SYNC PDO arrives in that time. But I don't know any device implementing this feature.

        SYNC  (period 5ms)
        0  window                5                       10 ms
        |----------|             |----------|            |----------|
  ______I________________________I_______________________I_________________
 D1        ii                                               ii
 D2      ii                       ii                      ii
 D3          ii                     ii	                      ii
 yours                                ii

* Device 1 is responding on each second SYNC * Device 2 is responding on each SYNC * Device 3 is responding on each SYNC * Your Device is responding on each SYNC after it has transmitted a SYNC PDO, which looks like it is responding on each second one. And with some luck, it fits into a SYNC window.

You can also see, that different devices may have different processing times for the SYNC. Important is sampling data on SYNC, transmitting these data within the SYNC-window. The picture doesn't show the arbitration of the messages on the bus.

oe 16.10.2002

Since CiA 301 version 4.1 the SYNC frame can have an optional data byte, the SYNC counter. Available for public since CiA 301 V4.2, April 2011.