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What's the difference between Modbus ASCII and Modbus RTU? |
Article Number: 382 | Rating: 2/5 from 4 votes | Last Updated: Wed, Mar 9, 2011 at 2:50 PM |
The original Modbus specification included two possible transmission modes: ASCII and RTU. Modbus RTU mode is the most common implementation, using binary coding and CRC error-checking. Modbus ASCII messages (though somewhat more readable because they use ASCII characters) is less efficient and uses less effective LRC error checking. ASCII mode uses ASCII characters to begin and end messages whereas RTU uses time gaps (3.5 character times) of silence for framing. The two modes are incompatible so a device configured for ASCII mode cannot communicate with one using RTU. Modbus ASCII messages require twice as many bytes to transmit the same content as a Modbus RTU message. For additional information, please see the Modbus Protocol Specification document, "PI-MBUS-300.pdf." |
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Read Commands from my Modbus Master to a ProSoft MCM Slave are working but Write Commands are failing. How do I fix this?
Viewed 1 times since Fri, Feb 8, 2008
I have multiple Modbus masters that need to communicate with 1 or more Modbus serial (RTU) slave devices. What product should be used??
Viewed 1 times since Tue, Jan 23, 2007
How can I detect the feedback status of individual command successful or failed?
Viewed 1 times since Wed, Nov 29, 2006
Do any Prosoft modules support Modbus UDP?
Viewed 1 times since Mon, Aug 24, 2015
How do you detect the individual Slave failure?
Viewed 1 times since Wed, Nov 29, 2006
I have a ProSoft Modbus Master solution and would like to know, is the Slave Status List the best place to monitor for communications health of the network?
Viewed 1 times since Tue, Mar 18, 2008
Why is the bit or coil level data incorrect?
Viewed 1 times since Tue, Nov 28, 2006
Can Modbus support redundant masters?
Viewed 1 times since Tue, Nov 28, 2006
How can a module's Modbus port, configured as a Slave port, detect communication loss with the Master port?
Viewed 1 times since Tue, Nov 28, 2006
I have limited or no experience with Modbus. How can I find out more about the protocol and command structure?
Viewed 1 times since Tue, Nov 28, 2006
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