EtherCAT® Sync

Overview

The EtherCAT® Master CM579-ETHCAT supports 2 modes for synchronized operation. These modes can be used for synchronization between PLC task and IO image.

The master has the same functionality as in unsynchronized mode, but with every new bus cycle it additionally creates an interrupt. With this interrupt the PLC task will be triggered.

System Requirements

The functionality described here has the following system requirements.

PLC	Firmware version 2.1.3
CM579-ETHCAT	Firmware version 2.4.11
Control Builder Plus	V2.1.0

Sync Mode 1

In this mode, the interrupt for task synchronization is generated at the end of the current bus cycle. If the PLC is triggered by this interrupt, it reads the input values at first. Then it starts the corresponding task. And at the end of the task, it writes the output values back to EtherCAT® Master. If the PLC task is not finished within a bus cycle a diagnosis message will be created.

Sync Mode 2

The difference between sync mode 1 and sync mode 2 is the instant of time when the interrupt is generated. In sync mode 2 it will be generated at the beginning of a bus cycle. The PLC task uses therefore the input values of previous bus cycle. If the PLC task is not finished within a bus cycle a diagnosis message will be created.

Diagnosis

2 error counters are available for diagnosis purposes. It can be read and evaluated within a PLC program using Function Block ECAT_SYNC: ECAT_SYNC ECAT_SYNCfrom EtherCAT® Library. More detailed information can be found in the corresponding documentation of this library EtherCAT_Library: ETHERCAT Library