Basics communication
EL6751
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Version: 3.5
4
Basics communication
4.1
EtherCAT basics
Please refer to the
for the EtherCAT fieldbus basics.
4.2
EtherCAT State Machine
The state of the EtherCAT slave is controlled via the EtherCAT State Machine (ESM). Depending upon the
state, different functions are accessible or executable in the EtherCAT slave. Specific commands must be
sent by the EtherCAT master to the device in each state, particularly during the bootup of the slave.
A distinction is made between the following states:
• Init
• Pre-Operational
• Safe-Operational and
• Operational
• Boot
The regular state of each EtherCAT slave after bootup is the OP state.
Fig. 28: States of the EtherCAT State Machine
Init
After switch-on the EtherCAT slave in the
Init
state. No mailbox or process data communication is possible.
The EtherCAT master initializes sync manager channels 0 and 1 for mailbox communication.
Pre-Operational (Pre-Op)
During the transition between
Init
and
Pre-Op
the EtherCAT slave checks whether the mailbox was initialized
correctly.
