As far as I understand, the Modbus is either defined for serial (RS232/RS485) or TCP/IP protocol layer. What does RTU and ASCII mode mean in that context? Do I have the possibility to operate Modbus in all of the following combinations:
- Serial and RTU
- Serial and ASCII
- TCP/IP and RTU
- TCP/IP and ASCII

 

RTU mode is binary, while ASCII mode is human readable verbose ASCII. They are both Serial. You should refer to the data at http://www.modbus.org for how to use Modbus. As far as _I_ know, you can use either RTU or ASCII over TCP.

Good luck,

Walt Boyes
Editor in Chief
Control magazine
www.controlglobal.com
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The choice between RTU and ASCII modes only exists in for Modbus serial connections. RTU mode is generally limited to direct connections where characters will not be delayed and cause a false end-of-message, while ASCII mode is used for modem and radio links where character delays become an issue. Modbus/TCP embeds an RTU message within the TCP packet and ignores character timing, so there is no requirement or option for ASCII mode.

Mike