EtherCAT Service Data Object (SDO)

Note: The RMC200 currently limits support for SDO communication to the Init Commands. In a future release, SDO communication will be supported from user programs.

A Service Data Object (SDO) is a block of data that is sent between the MainDevice and a SubDevice, only when specifically requested by the MainDevice. This is as opposed to Process Data Objects (PDOs) that are continuously communicated.

SDOs are typically used for accessing and modifying parameters or configuration settings in EtherCAT SubDevices. Init Commands utilize SDO communication. Examples of Service Data Objects (SDOs) are configuration data, operating modes, calibration values, etc. For example, the Init Commands that are communicated via SDOs can write the PDO configuration.

SDOs can also be used for data that needs to be regularly communicated, but not as frequently as the PDO data. For example, a drive has data that needs to be communicated every loop time of the RMC with PDOs, but perhaps the temperature information can be communicated less frequently via SDOs. In a future release, SDO communication will be supported from user programs for this type of information.

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