io folder explained
└── io
    ├── master.xml
    └── firmware            
        └── ec_{VendorID}_{ProductCode}_{RevisionNumber}.bin


master.xml contains the EtherCAT bus configuration. This file is created by using Motorcortex-ECAT.

ec _ {VendorID} _ {ProductCode} _ {RevisionNumber}.bin

This file is only required in case the slave’s SSI EEPROM is to small to hold the required data. How to create SII data check out Custom SII firmware.