According to the Modbus Serial Line Specification and Implementation Guide,…
2025
According to the Modbus Serial Line Specification and Implementation Guide, what is the default baud rate for a Regular-class Modbus RTU implementation when the preferred rate is implemented?
Answer: B. 19200 — ConceptA serial protocol can support several signalling rates while still defining a preferred default for interoperable configuration. In the Modbus Serial…
- A.
9600
- B.
19200
- C.
38400
- D.
57600
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Correct answer: B
Concept
A serial protocol can support several signalling rates while still defining a preferred default for interoperable configuration.
In the Modbus Serial Line guide, Regular-class devices support 9600 and 19200 bps; the default is 19200 bps when that rate is implemented, otherwise 9600 bps is the fallback.
Application
The stem explicitly asks for a Regular-class implementation with the preferred rate available. Therefore the applicable default is 19200 bps.
Contrast
9600 bps is the fallback default when 19200 bps is not implemented and is also the Basic-class rate.
38400 bps may be offered as an additional configurable rate, but it is not the guide’s preferred default.
57600 bps may likewise be offered as an additional configurable rate rather than the required default.
Cross-check
The guide’s implementation-class table lists the Regular-class default as 19200 bps, with the explicit fallback to 9600 bps. This matches the condition stated in the question.