Understanding and Troubleshooting Modbus
EcoStruxure Building Operation, TAC IA Series, Other
All Modbus environments.
Modicon first introduced Modbus in 1979. Modbus is an open standard,and it is the most widely used in the industrial environment. Modbus is publicly available and,due to its simplicity, many manufacturers use Modbus as a solution for integration in their own products. Many commercial products and systems support the Modbus RTU and Modbus TCP protocols. For further information, visit the Modbus website at http://www.modbus.org.
For a brief understanding on Modbus and how to troubleshoot Modbus: Modbus Troubleshooting.pdf