12.2 EtherCAT State Machine
12-3
12
EtherCA
T Communications
12.2
EtherCAT State Machine
The EtherCAT state machine is used to manage the communications states between the mas-
ter and slave applications when EtherCAT communications are started and during operation, as
shown in the following figure. Normally, the state changes for requests from the master.
State
Description
INIT
•
Mailbox communications are not possible.
•
Process data communications are not possible.
INIT => PRE-OP
•
The master sets the DL address and Sync Manager channels for mailbox communi-
cations.
•
The master initializes DC clock synchronization.
•
The master requests the Pre-Operational state.
•
The master sets the AL control register.
•
The slaves check whether the mailbox was initialized correctly.
PRE-OPERATIONAL
(PREOP)
•
Mailbox communications are possible.
•
Process data communications are not possible.
PREOP => SAFEOP
•
The master sets the Sync Manager channels and FMMU channels for process data.
•
The master uses SDOs to set the PDO mappings and the Sync Manager PDO
Assignment parameters.
•
The master requests the Safe-Operational state.
•
The slaves check whether the Sync Manager channels for process data communi-
cations and, if required, the distributed clock settings are correct.
SAFE-OPERA-
TIONAL
(SAFEOP)
•
Mailbox communications are possible.
•
Process data communications are possible. However, only the input data is valid.
The output data is still not valid.
SAFEOP => OP
•
The master sends valid output data.
•
The master requests the Operational state.
OPERATIONAL
(OP)
•
Mailbox communications are possible.
•
Process data communications are possible.
INIT
PRE-OPERATIONAL
SAFE-OPERATIONAL
OPERATIONAL
Power ON
(IP)
(PI)
(SP)
(PS)
(OP)
(OI)
(SI)
(SO)
(OS)
