SDO services READ and WRITE

The user interface of the SDO service is displayed differently depending on the EtherCAT® master or programming environment.

Certain sizes and information on the performance of the service are always required:

SDO READ service

Description

Slave address (16 bit)

EtherCAT® address of the inverter from which data is to be read.

Index (16 bit)

Subindex (8 bit)

Address in the object directory of the inverter that is to be read.

SDO WRITE service

Description

Slave address (16 bit)

EtherCAT® address of the inverter to which data is to be written.

Index (16 bit)

Subindex (8 bit)

Address in the object directory of the inverter that is to be written.

Data

Structure in which the data to be written is stored.

Data length

Length of the data that is to be written.

Additional flags and parameters may be required:

  • For activating the function
  • For "In-process messages" or error messages
  • For timeout monitoring

To be able to use the non-cyclical parameter access, the manufacturer of the EtherCAT® master usually provides corresponding libraries and function blocks.

The following libraries and function blocks are required for the EtherCAT® master from Beckhoff Automation GmbH:

Library

Function blocks

Tc2_EtherCAT.lib

(Standard.Lib, TcBase.Lib, TcSystem.Lib, TcUtilities.Lib)

Read: FB_EcCoeSdoRead

Write: FB_EcCoeSdoWrite

For more information on error numbers, refer to the Beckhoff InfoSys.

INFORMATION

With a double-axis module, you can access the second axis of the module via an index offset of 0x1000 (4096 dec).