User Manual Of EL7-EC** AC Servo
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7.3 EtherCAT state machine
EtherCAT state machine, commonly known as "communication state machine ", is mainly
used to manage communication between master and slave stations. The communication
function mainly includes mailbox and process data communication. The EtherCAT state
machine transition relationship is shown in figure 6.3
Init
Pre-Operational
Safe-Operational
Operational
(IP)
(SP)
(PI)
(PS)
(OP)
(OI)
(OS)
(SO)
(SI)
Low
High
Figure 7.3 EtherCAT state machine transitions
EtherCAT state machine transitions have the following characteristics
：
①
From initialization to operational, the conversion must be carried out strictly in the
order of initializing > pre-operational > safe operational > operational, from low to high,
and no grade skipping is allowed
②
When converting from high to low, grade skipping is allowed.
③
If state transition request to master station fails, slave station will send an error
message to the master station.
EtherCAT 402 State Machine Communication function
State and transition
Communication function
Init
No mailbox or process data communication is possible.
Pre-Operational
Mailbox communication is effective, no process data communication, SDO
function is valid
Safe-Operational
Mailbox communication and sending process data object is valid, SDO and
TXPDO are valid
Operational
Mailbox communication, receive and send process data object valid, SDO
、
RXPDO and TXPDO valid
