There are several versions of the Modbus protocol because the protocol was originally developed for serial connections but has been adapted for the networking world. These include:
- Modbus ASCII – Original serial version. Data is transmitted in ASCII characters, which makes it easy to troubleshoot when there are problems
- Modbus Plus – An extended, proprietary version that runs on RS485
- Modbus RTU – Serial protocol that transmits data in binary form, making data more compact and transmission more efficient than the ASCII version. More commonly used than Modbus ASCII. (Based on Serial communication like RS485, RS422, and RS232.)
- Modbus TCP/IP – The TCP/IP encapsulated version of Modbus. (Based on Ehternet.)
