Bus Devices KNX Basic: exam questions with worked answers

Questions for the "Bus Devices" topic

1. Q01

   Among the following Group Object flags, which one must be enabled so that the device transmits a telegram whenever the object's value changes?

   • A.Flag C (Communication)
   • B.Flag T (Transmit)
   • C.Flag W (Write)
   • D.Flag U (Update)

   3. Bus Devices· Gruppenobjekt-Flags· Medium

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   Correct answer

   B — Flag T (Transmit)

   Learning tip

   The T (Transmit) flag enables spontaneous transmission of a telegram whenever the local value of the Group Object changes. C is a prerequisite that enables communication overall but does not by itself trigger sending. W allows receiving write requests from the bus. U handles updating the local value upon receipt of a Group Value Response telegram. Without T, the device can receive values but never sends its own.

   Source: Porto KNX — Bus Devices, Flags

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2. Q02

   DPT 1.001 (Switch) and DPT 1.008 (UpDown) have the same bit length and the same binary structure; only their semantic meaning differs.

   TrueFalse

   3. Bus Devices· DPT (Datapoint Types)· Medium

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   Correct answer

   True

   Learning tip

   Both DPTs belong to the 1.xxx family, which is encoded on a single bit (boolean). DPT 1.001 = Switch (on/off for general switching), DPT 1.008 = UpDown (up/down for shutters and blinds). The semantic distinction allows ETS to display the appropriate labels and icons, and lets applications behave consistently with the user's expectations.

   Source: KNX Specifications V3.0.0 (public) — Datapoint Types, Vol. 3/7/2

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