Explanation network variables

Network variables

The EL66xx support sending/receiving network variables. This applies for the EL6601 as of Firmware 07, for the EL6614 as of Firmware 03.

A maximum of 32 for each, publishers and subscriber, are permitted per EL66xx.

Hardware replacement If the system was designed with a previous EL6601 version (EL6601-0000-0000), this can be replaced with versions from EL6601-0000-0017 without problem. If the system was designed for version EL6601-0000-0017 or higher, replacement with a previous version is not possible due to unsupported network variables.

Network variables are specially configured Ethernet frames that enable Beckhoff devices to communicate with each other in real-time via Ethernet. Such device can send (publisher) or receive (subscriber) messages.
An Ethernet frame is sent for each publisher (Ethernet-based). A maximum of 1500 bytes of data can thus be sent per publisher. Within a publisher/subscriber several variables (publisher and subscriber variables) can be created.
Generally, several publishers/subscribers can be configured for each sending/receiving device (e.g. IPC or EL6601).

Based on the sample of a data sender the hierarchy therefore consists of

• the sending device with a minimum of one Ethernet interface: IPC, CX, FC9011, EL6601, ...
• 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 publishers - each publisher is sent as an independent Ethernet frame and can therefore contain 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

On the receiver side the configuration is mirrored.

The EL66xx can also process publishers and subscribers which are frame data

• Max. 32 publishers and/or subscribers
• For each transmit direction (publisher or subscriber) the following maxima apply:
• all publishers: 1024 bytes total data
• all subscribers: 1024 bytes total data

Update of the terminal The values above apply for a EL6601/6614-0000-0018. Version -0017 only supports a maximum of 300 bytes per publisher/subscriber. If a -0017 terminal is used, the values specified above can be achieved by an update to revision -0018. Please contact our technical support.

With appropriate EtherCAT cycle time and depending on the scale and number of the publishers/subscribers configured in the EL66xx, real-time cycle times down to 500 µs or below are possible.

Typical throughput values for EL6601, FW08, Rev. EL6601-0000-0018 are

• 1 publisher with 1000 bytes, 1 subscriber with 1000 bytes, simultaneous bidirectional operation: 2 ms
• 1 publisher with 100 bytes, 1 subscriber with 100 bytes, simultaneous bidirectional operation: 300 µs

Both characteristic values were determined with this sample program . TwinCAT from version 2.11 is required for the *.tsm System Manager file.

The EL6601 is used as a sample to explain configuration as publisher or subscriber for network variables. The dialogs under TwinCAT 2.10 and TwinCAT 2.11 here are slightly different.

The following descriptions of the dialogs of the EL6601 in the TwinCAT System Manager can be applied equally to the EL6614.

Note regarding the term total data

For each data direction the EL6601/EL6614 from Rev. -0018 can transfer a maximum of 1024 byte total data. The total data consist of the user data (e.g. a UDINT) and the diagnostic data for the EL66xx.

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 data quantity exceeds 1024 bytes, a corresponding message window appears when activation is attempted:

Note regarding the data quantity

The EL66xx (EL6601 from FW07, EL6614 from FW03) has an 8 kbyte data memory with the following default allocation

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