Parameterization and commissioning
EL6751
128
Version: 3.5
Fig. 129: Flow chart for CAN cycle (Sync Multiplier = 1)
Synchronization with SM2 (SM3) event
When receiving the EtherCAT process data telegram, the SM2 event (SM3 if no EtherCAT output data are
configured, i.e. only CANopen slaves without CAN RxPDOs) is generated by the EtherCAT slave controller,
thus starting the CAN cycle. If synchronous CAN PDOs are configured, they will be dealt with at the
beginning. Following the preparation of CAN transmit PDOs, the SYNC message will initially be sent.
Because some CANopen slaves react strangely if their RxPDOs are received before they have sent their
TxPDOs, a delay can be set for the TxPDOs in 0xF800:0E. After sending the SYNC message, the EL6751
waits until this delay has expired before sending any further CAN messages. After that, the synchronous
RxPDOs are transmitted first, followed by the asynchronous RxPDOs (if they have changed or if the event
time has expired). If the synchronous RxPDOs have been sent, the expiry of the input shift time is waited for.
Subsequently, the receipt of the synchronous TxPDOs is checked. If the transmission type of a TxPDO is set
to 1, the EL6751 expects a RxPDO in each cycle until the time T4; if this has not been received, the Node
State of the CANopen slave (0xF102:yy) is set to 0x28 for one cycle. If the next SM2 (SM3) event is received
before the CAN cycle is completed, the Cycle Exceed counter (0x1C32:0B or 0x1C33:0B) is incremented
and a CAN cycle is omitted.
