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What is the difference between Modbus RTU and Modbus ASCII protocol?

April 26, 2017ASCII difference modbus Protocol RTU

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What is the difference between Modbus RTU and Modbus ASCII protocol?

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The primary difference is that Modbus RTU uses Hex where as Modbus ASCII uses Hex ASCII. In RTU function code for a holder register is set as one byte 0x03 in ASCII it is sent as 0x30 0x33, 2 bytes. Additionally a Modubs ASCII packet starts with a colon (:). Usually the devices that I see now that use Modbus ASCII are legacy devices typically pumps and flow meters still used in the Petroleum Industry.