Transmission Mode - 3onedata GW11 Series User Manual

11.4 Transmission mode

Modbus RTU
When devices communicate on a MODBUS serial line using the RTU (Remote
Terminal Unit) mode, each 8–bit byte in a message contains two 4–bit hexadecimal
characters.
Key Benefits: Higher data density, higher throughput rates at the same baud rate than
ASCII mode, and more data.
Interoperability between Modbus devices only each device has the same mode RTU
or ASCII, the default setting must be RTU mode.
The RTU message frame is as follows:
Modbus ASCII
When devices are setup to communicate on a MODBUS serial line using ASCII
(American Standard Code for Information Interchange) mode, each 8–bit byte in a
message is sent as two ASCII characters.
This mode is used when the physical communication link or the capabilities of the
device does not allow the conformance with RTU mode requirements regarding timers
management.
Advantages: The time interval for sending characters can be up to 1 second

without error.
Disadvantages: Since one byte requires two characters, this mode is less

efficient than RTU.
ASCII message frame is shown below.
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(I)GW11XX Modbus User Manual
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