●
State Machine
Within the EtherCAT
®
protocol stack several state machines exist. From
an EtherCAT
®
application
’
s point of view the EtherCAT
®
State Machine
(ESM) is the most important one. The role of the ESM is to inform the
application about the communicative state of the underlying EtherCAT
®
field bus environment. Every EtherCAT
®
device (both master and slave)
contains an ESM. The ESM reflects the current communicative state of an
EtherCAT
®
device. Figure 11.65 shows all ESM states and possible state
transitions.
Initial
Bootstrap
Pre-operational
Safe operational
Operational
A
E
B
C
D
Figure 11.65:
EtherCAT
®
State Machine diagram
A Init state
After EtherCAT
®
protocol stack initialization, the system enters the
Init
state. The
Init
state defines the root of the communication
relationship between master and slave in the application layer. No
direct communication between the master and slave is possible in this
state. The master uses the
Init
state to initialize a set of slave
configuration registers. If the slave supports mailbox communication,
which Genesis systems do, the corresponding sync manager
configurations are also done in the
Init
state.
B Pre
-
operational state
In the
Pre
-
operational
state mailbox communication is active. Both
the master and slave can use the mailbox and the appropriate
protocols to exchange application specific initializations and
parameters. No process data communication is possible in this state.
C Bootstrap state
The optional Bootstrap state allows slave firmware downloads using
the File over EtherCAT
®
(FoE) protocol.
GEN3t
I3995-3.1 en HBM: public
233
