EtherCAT Overview

The Automation1 controller supports the EtherCAT slave protocol.

EtherCAT-Related Terms

• EtherCAT

  • Ethernet for Control Automation Technology is a real-time communication protocol over standard Ethernet hardware / networks.

• Master / Slave

  • In EtherCAT, the network topology has one master controller that communicates with up to N (65,535) slave controllers. The maximum number of slave devices is limited by bandwidth restrictions.

• TwinCAT

  • The Windows Control and Automation Technology platform. This platform is an EtherCAT master controller.

• ESI

  • The EtherCAT Slave Information file defines the capabilities of the entire EtherCAT slave device. This file is imported by the EtherCAT master software when you configure the EtherCAT network.

• PDO

  • Process Data Objects make up the real-time application data transfer protocol over the EtherCAT network. The ESI file defines the layout of data in the PDO space.

    • Rx PDO: data received from the master device by the slave device.

    • Tx PDO: data sent to the master device from the slave device.

EtherCAT ESI Definition File

The EtherCAT Slave Information (ESI) definition file is titled Automation1EtherCAT.xml. The EtherCAT master imports the ESI file, which defines the object dictionary of the Automation1 controller and defines the layout of data in the Process Data Object (PDO) space.

Table: EtherCAT ESI Definition File

Controller Data Layout

Data Access

Automation1 uses Industrial Ethernet mappings to expose the PDO space of EtherCAT. These Industrial Ethernet mappings connect the memory regions of the EtherCAT data to arbitrary controller data types. The table that follows shows the access level of the registers.

Table: Register Access

You can configure the fields that follow for each Industrial Ethernet mapping:

• Name
  • The name of the variable. The name is automatically converted into an AeroScript variable by the controller. You can then use it in programs or libraries.
• Count
  • The count determines how many consecutive sequences there are of this variable. With counts greater than 1, the controller accesses the variables like an array. You can access the variables through an Industrial Ethernet mapping array.
• Type

  • The type lets you configure EtherCAT data as different data types. The data types that follow are supported.

  Table: Supported Data Types

  Data Type	Description
  UInt8	8-bit unsigned integer
  UInt16	16-bit unsigned integer
  UInt32	32-bit unsigned integer
  Int8	8-bit signed integer
  Int16	16-bit signed integer
  Int32	32-bit signed integer
  Float32	32-bit single-precision floating-point value
  Float64	64-bit double-precision floating-point value

  • The address range for integer variables starts at byte address 0. For integer variables, Aerotech recommends that you select the UInt32 data type for consistency with the ESI definition file.

  • The address range for real variables starts at byte address 256. For real variables, Aerotech recommends that you select the Float64 data type for consistency with the ESI definition file.

• Byte Address
  • This configures the byte offset of the register.
• Bit Address
  • This configures the bit offset of the register.

  • The final address is the sum of byteAddress * 8 + bitAddress.

  • Non-bit data types must be 8-bit byte aligned

• Comment
  • You can add a comment about the mapping.

Use Automation1 Studio to configure Industrial Ethernet mappings. Refer to the sections that follow for examples. For information about how to configure Industrial Ethernet mappings, see the Industrial Ethernet Tab section of the Variables & I/O module page. This module is part of the Develop workspace.

Industrial Ethernet Mappings Example

After you configure the Industrial Ethernet mappings, the controller automatically converts the information into AeroScript properties that you can edit.

Figure: Configured Industrial Ethernet Mappings

The code that follows is an example of the AeroScript properties after mapping.

property $Commands_Real_0 as real
property $Commands_UInt[$index as integer] as integer
property $Results_Real[$index as integer] as real
property $Results_UInt_0 as integer

To configure EtherCAT mappings, go to the Configure EtherCAT Mappings section of the Configure Automation1 for EtherCAT page.

EtherCAT Status Items / Data Collection

Automation1 supplies many EtherCAT status items that you can use directly or through Data Collection. All of the EtherCAT status items are in the System category. You can access the EtherCAT status items with the StatusGetSystemItem() function. You can add the EtherCAT status items to Data Collection with the DataCollectionAddSystemSignal() function.

To get status information for the client and the server configurations, use the status items that follow:

• EtherCAT Connected

• EtherCAT Error

To get the total size in bytes of the PDO data for Rx and Tx channels, use the status items that follow:

• EtherCAT Rx Pdo Size

• EtherCAT Tx Pdo Size

To access the data that is sent over the EtherCAT connection, use the status items that follow:

• EtherCAT Rx Pdo

• EtherCAT Tx Pdo

The Rx status items and the Tx PDO status items must have one more data field to specify the connection index, data type, byte offset, and bit offset. To determine the correct additional data value, refer to the computeEthercatAdditionalData() AeroScript example function that follows. If you want to use this function, you must add the code to your AeroScript program.

• $Index – The index of the connection as defined in Automation1. The first created connection is index 0. To see the currently defined connections, go to the Variables & I/O module in the Develop workspace and open the Industrial Ethernet tab. For more information about this tab, see Industrial Ethernet Tab.
• $DataType – The type of the data.
• $BitOffset – The bit offset of the data item as defined in the EtherCAT mapping.
• $ByteOffset – The byte offset of the data item as defined in the EtherCAT mapping.

function computeEthercatAdditionalData($Index as integer, $DataType as EthercatRegisterDataType, $BitOffset as integer, $ByteOffset as integer) as integer
     var $additionalData as integer
					
     $additionalData = ($Index << 28) & 0xF0000000 | ($DataType << 23) & 0x0F800000 |($BitOffset << 20) & 0x00700000 | ($ByteOffset & 0x000FFFFF)
					
     return $additionalData
end

program
     $iglobal[0] = computeEthercatAdditionalData(0, EthercatRegisterDataType.Float64, 0, 256)
end

Networking

EtherCAT networks are built with standard Ethernet RJ45 hardware, running full-duplex Ethernet physical layers. Thus, you can implement real-time communication networks with commercial, off-the-shelf networking hardware.

EtherCAT controllers have either one or two Ethernet interfaces and are typically built in a ring-based topology. Data flows from the master device to each of the interconnected slave devices and then back to the master device in a ring. The network is redundant and supports one of the links going down, as data can flow full-duplex through the hardware, forming two individual daisy chain networks.

The Automation1 controller has two Industrial Ethernet ports labeled A and B. For EtherCAT, port A is the input port and port B is the output port. Use port A to connect the controller to the EtherCAT network. Port B is optional. You can use it to connect to more EtherCAT devices on the same network.

Figure: Industrial Ethernet Ports

Bandwidth

The Automation1 controller hardware has 100BASE-TX, which allows for communication of 100 Mbps. An EtherCAT network that uses 100BASE-TX can theoretically send a maximum of 12,080 bytes while maintaining a 1ms update rate.

The Automation1 EtherCAT ESI definition uses 64 32-bit unsigned integers and 64 64-bit floats. This PDO space uses 768 bytes, which is approximately 6% of 1ms bandwidth.

Licensing

The Industrial Ethernet (-IE) licensing option of Automation1 supports these EtherCAT stacks on the controller:

• -IE1: No EtherCAT support

• -IE2: EtherCAT support