Ethercat State Machine - Leadshine EL8-EC Series User Manual

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 7.3
Figure 7.3 EtherCAT state machine transitions
① From initialization to operational, the conversion must be carried out strictly in the order
EtherCAT state machine transitions have the following characteristics：
of initializing > pre-operational > safe operational > operational, from low to high, and no
② When converting from high to low, grade skipping is allowed.
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
Init
Pre-Operational
Safe-Operational
Operational
Init
(IP)
(PI)
Pre-Operational
(PS)
(SP)
(OI)
(OP)
Safe-Operational
(SO)
(OS)
Operational
Communication function
No mailbox or process data communication is possible.
Mailbox communication is effective, no process data communication, SDO
function is valid
Mailbox communication and sending process data object is valid, SDO and
TXPDO are valid
Mailbox communication, receive and send process data object valid, SDO、
RXPDO and TXPDO valid
User manual of EL8-EC***F AC Servo
Low
(SI)
High
293