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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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Why is the bit or coil level data incorrect?
Viewed 1 times since Tue, Nov 28, 2006
How do I monitor the health of coms to my slaves when the module is a Master?
Viewed 1 times since Wed, Nov 29, 2006
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
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
Can Modbus support redundant masters?
Viewed 1 times since Tue, Nov 28, 2006
What Modbus address would we need to put into the MODSIM32 simulator if we specified on the MVI56-MCM device address to 8680HEX (-31104 decimal) when the MVI56-mcm is the slave?
Viewed 1 times since Tue, Nov 28, 2006
How do I enter a Modbus address of 40001 or higher in the DevAddress command field of my MVI56-MCM?
Viewed 1 times since Tue, Nov 28, 2006
Why are my PLX gateway modbus serial commands not executing despite being enabled?
Viewed 1 times since Wed, Aug 12, 2015
If I am reading the value from ProSoft 4x register, and it represents a digital input or digital output, how is the value stored?
Viewed 1 times since Tue, Nov 28, 2006
Defining the Slave ID when issuing Modbus Broadcast write commands
Viewed 1 times since Tue, Nov 28, 2006
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