**EtherCAT ESI File**

The ESI (EtherCAT Slave Information) file contains the device description required by EtherCAT configuration software to correctly identify and configure the product.

The ESI version must be compatible with the firmware version installed on the product. Therefore, the ESI file must be updated whenever the product firmware is updated.

The ESI is provided in two formats:
	.xml – the standard ESI format.
	.bin – a binary format supported by certain configuration tools.
	
Both formats can be used to update the ESI using TwinCAT.

**NOTE:** CODESYS users must use the .bin file. CODESYS does not properly support updating the ESI from the .xml file, even though it may indicate that the operation was completed successfully.

**IMPORTANT:** Always use the ESI file corresponding to the firmware version installed on the product.