You can test the system with your actual hardware (e.g. solar inverter + NI cRIO system as EtherCAT master). If you don’t have access to the hardware right now, testing case be done using a Modbus Slave simulator (we recommend this simulator with a 30 day free trial) and Beckhoff TwinCAT 3 (to act as EtherCAT Master). If using TwinCAT, copy the XML file produced under the previous step into the appropriate TwinCAT directory.
An example set of inputs for the Modbus slave simulator is shown below.

For example, the number 25 is entered for register 304. This register now appears in TwinCAT under byte 6. Our first register is register 301. In Modbus, each register is 16 bits, or 2 bytes. As a result, register 301 is represented on the EtherCAT side as bytes 0 and 1, register 302 is represented by bytes 2 and 3, register 303 is represented by bytes 4 and 5, and finally register 303 is represented by bytes 6 and 7. The convention that TxPDOs are written as an array of bytes into the exported XML seems to be somewhat baked into the SYNCON XML export tool. However, we are currently exploring if there are other/smarter (e.g. Word aligned) export options.
