Beckhoff network variables

The EP6601-0002 supports the sending and receiving of network variables.

A maximum total of 32 Publisher and Subscriber per EP6601-0002 is permitted.

Network variables are specially configured Ethernet frames that enable Beckhoff devices to communicate with each other in real-time via Ethernet. Such a device can be a sender of messages (Publisher) or a recipient (Subscriber).
One Ethernet frame is sent per Publisher (Ethernet-based). A maximum of 1500 bytes of data can thus be sent per Publisher. Several variables - the Publisher or Subscriber variables - can be created within a Publisher/Subscriber.
Several Publisher/Subscriber can usually be configured for each sending/receiving device (e.g. IPC or EP6601-0002).

The hierarchy of a data sender, for example, consists of

• the sending device with at least one Ethernet interface: IPC, CX, FC9011, EP6601-0002, ...
• FastEthernet/100 Mbit and 1 Gbit are supported
• this Ethernet interface is configured in the local TwinCAT System Manager as a real-time Ethernet device
• 1..n configured Publisher - each Publisher is sent as a separate Ethernet frame and can therefore comprise a maximum of 1500 bytes
• 1..n Publisher variables contained therein for linking with the task/PLC
• for each Publisher variable the user data and diagnostic data are transferred

The configuration is mirrored on the receiver side.

The EP6601-0002 can also process Publisher and Subscriber independently, the framework data are

• max. 32 Publisher and/or Subscriber
• per transmission direction (Publisher or Subscriber) are maximum permissible in total
• all Publisher: 1024 bytes total data
• all Subscriber: 1024 bytes total data

Note on the term total data

The EP6601-0002 can transmit a maximum of 1024 bytes of total data per data direction. The total data consists of the user data (e.g. a UDINT to be transmitted) and diagnostic data from EP6601-0002.

Formula for number of diagnostic data bytes

• Publisher direction: 2 + ((number of Publishers) * 2)
• Subscriber direction: 2 + ((number of Subscriber variables) * 4)

If the configured amount of data exceeds 1024 bytes, this is indicated by a message window when an activation attempt is made:

Note regarding the amount of data

The EP6601-0002 has 8 kbyte of usable memory, which is allocated as follows by default

If more Publisher or Subscriber data are required for an application, the SyncManagers can be modified accordingly. The mailbox cannot be modified.

• Notes