12.3 EtherCAT (CoE) Communications Settings
12.3.1 Normal Device Recognition Process at Startup
12-5
12
EtherCA
T Communications
12.3
EtherCAT (CoE) Communications Settings
You can use EtherCAT secondary addresses (station aliases) to identify devices or to specify
addresses.
12.3.1
Normal Device Recognition Process at Startup
When communications are started, the master uses auto-increment addressing to detect the
slaves. The Identity objects read from the slaves are compared with the master configuration
information (set in advance with an EtherCAT configuration tool). Therefore, the slaves must
normally be connected in the network in the same order as they appear in the master configu-
ration. However, you can define station aliases to enable using other network topologies.
12.3.2
Application Example
With a machining center, there may be two identical drives for operation in the X and Y direc-
tions. When a device is replaced, there is a chance that the cable may be connected in the
wrong order. To prevent the drives from receiving incorrect process data, you can use station
aliases to use explicit addresses for the drives.
12.3.3
Device Recognition with Station Aliases
The master uses auto-increment addressing to read the station aliases. It then compares the
detected station aliases with the master configuration to get the topology that was set as the
network topology.
Station Alias Register (0x0012)
The station alias is set in the ESC Configured Station Alias register when the power supply is
turned ON.
The value of the register can be read as follows:
Configured station alias = (S1 set value)
×
16 + (S2 set value)
S1:
Upper four bits
of EtherCAT
secondary address
S2:
Lower four bits
of EtherCAT
secondary address
