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vacon • 7
EtherNet/IP - General info
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2.1.1
ACD (Address Conflict Detection)
The VACON® 100 Family AC drives implement ACD algorithm (IETF RFC 5227). The implementation
includes requirements from the EtherNet/IP protocol.
The ACD algorithm tries to actively detect if the IP address configured to this device is been used by
another device in the same network. To accomplish this, ACD sends four ARP request packets when
the device's Ethernet interface goes up or when its IP address changes. ACD prevents the use of the
Ethernet interface until the ARP probing finishes. This delays the startup of fieldbus protocols about
one second. During the delay or after it, the ACD passively checks incoming ARP messages for use
of the device's IP address. If another device with the same IP address is detected, the ACD will try
to defend its IP address with a single ARP message. If the other device with the same IP address
also supports ACD, it should stop using the address. If not, the ACD will close the Ethernet connec-
tion and indicate the situation with an alarm. This is done according the "DefendWithPolicyB". You
cannot acknowledg the alarm if the problem is active. The ACD opens Ethernet connection if the
other device with the same IP address disappears from the network. You can acknowledge the
alarm after this.
Other policies are not supported. If the fieldbus protocol has been active, a fieldbus fault may be
activated (depends on the fieldbus and drive application configuration).
2.1.2
Technical details
EtherNet/IP is a connection-oriented communication protocol designed for use in industrial envi-
ronments. The protocol allows simple and complex industrial devices to communicate with each
other.
Standard Ethernet and TCP/IP technology is used by the EtherNet/IP protocol. There are different
messaging forms in EtherNet/IP:
•
Connections are established using so-called "Unconnected Messaging”,
•
Real-time I/O data transfer happens through "Connected Messaging”
There are two kinds of connections in EtherNet/IP:
•
General-purpose, point-to-point connections are known as "Explicit Messaging Connec-
tions". These messages are sent using the TCP protocol.
•
Connections for moving application-specific I/O data at regular intervals are known as
"Implicit Connections" or "I/O Data Connections". These messages are sent using the UDP
protocol
