Datalogic AMT58 Series Manual page 147

AMT58x-EC EtherCAT®
6.1.7 EtherCAT State Machine (ESM)
EtherCAT Slave is a state machine; communication and operating
characteristics depend on the current state of the device:
 INIT: it is the default state after power on; in this state there is not
direct communication between Master and Slave on the
Application Layer; some configuration registers are initialized and
the Sync Managers are configured;PRE-OPERATIONAL: in this
state mailbox is active; both Master and Slave can use the
mailbox and its protocols for exchanging specific initialization
parameters of the application. Exchange of Process Data (PDO)
is forbidden;SAFE-OPERATIONAL: in this state Master and Slave
can issue only input process data, while output process data are
still in SAFE-OPERATIONAL
Master and Slave are enabled to send both input process data
and output process data.
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state;OPERATIONAL: in this state