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
Type | Usable extent | Operation mode | Used memory |
|---|---|---|---|
Mailbox Out | 1024 bytes |
| 1024 bytes (fixed) |
Mailbox In | 1024 bytes |
| 1024 bytes (fixed) |
Publisher | 1024 bytes | 3-buffer mode | 3072 bytes |
Subscriber | 1024 bytes | 3-buffer mode | 3072 bytes |
If more Publisher or Subscriber data are required for an application, the SyncManagers can be modified accordingly. The mailbox cannot be modified.