Basic function principles

EL6851 (Master)

The EL6851 connects the EtherCAT system to the DMX protocol. The EL6851 DMX EtherCAT terminal is a DMX master and transmits data to the individual devices. A maximum of 512 bytes of user data can be transmitted. The number of data to be transmitted can be set via the process data. Furthermore, the terminal can be set to RDM mode, in which the DMX devices that support the RDM protocol can be parameterized or also configured. The RDM protocol must be programmed in the controller; the EL6851 offers only Layer 2 functionality. Corresponding RDM blocks are available to TwinCAT users.

Process data

Full process image: for the use of the RDM protocol and DMX up to 512 bytes of user data.

Basic function principles 1:
TwinCAT tree, process image up to 512 bytes of user data

Minimal process image: no RDM possible and DMX up to 64 bytes of user data

Basic function principles 2:
TwinCAT tree, process image up to 64 bytes of user data

Input process data

Basic function principles 3:
TwinCAT tree DMX status, input process data

Transmit accepted
Data have been transmitted (required only for the RDM protocol)

Receive toggle
This bit is toggled if data are received from the slave (required only for the RDM protocol)

Cyclic TxD disabled
No data are transmitted if this value is TRUE

Default data sent
Default data are transmitted if this value is TRUE (see index 0x8000:12)

Frame sent toggle
This is toggled at each EtherCAT frame

TxPDO Toggle
This is toggled after each DMX frame

Channel length
Number of data received (required only for the RDM protocol)

Start code
Start code of the DMX protocol (required only for the RDM protocol)   

DMX Channel:
ARRAY[1 - 64] Receive buffer in which the response of the RDM device is located (required only for the RDM protocol)

Output process data

Basic function principles 4:
TwinCAT tree DMX status, output process data

Transmit request
This bit is toggled in order to transmit data (required only for the RDM protocol)

Disable cyclic TxD
No data are transmitted if this value is TRUE

Send default data
Default data are transmitted if this value is TRUE (see index 0x8000:12)

Channel length
Number of data to be transmitted via DMX or RDM

Start code:
Is always 0x00. Only for the RDM protocol 0xCC (required only for the RDM protocol)

Basic function principles 5:

Channel length

To enable data to be transmitted via the DMX terminal, the ‘Channel Length’ must not be equal to zero. The length specifies the number of user data, maximum 512 bytes.

Predefined PDO Assigments (Master)

The "Predefined PDO Assignment" enables a simplified selection of the process data. The desired function is selected on the lower part of the "Process Data" tab. As a result, all necessary PDOs are automatically activated and the unnecessary PDOs are deactivated.

The following PDO assignments are available:

Basic function principles 6:
Prededined PDO Assigments Master EL6851

EL6851-0010 (Slave)

Process data

Full process image: For the use of up to 512 bytes of user data.

Basic function principles 7:
TwinCAT tree DMX slave, process image up to 512 bytes of user data

Minimum process image up to 64 bytes of user data

Basic function principles 8:
TwinCAT tree DMX slave, process image up to 64 bytes of user data

Input process data

Basic function principles 9:
TwinCAT tree DMX status (slave), input process data

Receive toggle
This bit is toggled if data are received from the slave (required only for the RDM protocol)

Framing error
Incorrect start code (not NULL) or the next frame was detected during a transmission

Overrun error
Overflow of internal receive buffer

TxPDO State
Received data are invalid

TxPDO Toggle
This is toggled after each DMX frame

Channel length
Number of data received (required only for the RDM protocol)

Start code
Start code of the DMX protocol (required only for the RDM protocol)   

Predefined PDO Assigments (Slave)

The "Predefined PDO Assignment" enables also for the EL6851-0010 a simplified selection of the process data. The desired function is selected on the lower part of the "Process Data" tab. As a result, all necessary PDOs are automatically activated and the unnecessary PDOs are deactivated.

The following PDO assignments are available:

Basic function principles 10:
Predefined PDO Assigments Slave EL6851-0010

Sample program

In this sample program, two EL6851-0010 each receive 64 bytes of data from the EL6851 master. The PDO settings are explained for this.