Modbus Poll Software
Modbus Poll is a useful software tool for testing Modbus RTU and Modbus TCP communication. Modbus Poll is a Modbus master that has read and write functions and has the capability of capturing communication traces. The software can be used on a trial basis, which disconnects communication every 10 minutes. A license can be purchased at a reasonable price. See their website at http://www.modbustools.com/modbus_poll.asp.
We use Modbus Poll for testing Modbus communication on the AKD and S200-CNS servo drives, and the P7000 stepper drive.
Attached is an example Modbus Poll configuration file used for connecting to an AKD drive.