Guide

#Model and limits

BusDiagram is a diagram design tool; its simulation layer exists to illustrate the diagrams and makes the following choices. They describe the software model and should not be taken as a complete account of a physical KNX installation.

• Timing: propagation is slowed for inspection; it does not reproduce real twisted-pair bus timing.
• Group services: GroupValueWrite, GroupValueRead, and GroupValueResponse are modeled. Individual-address programming telegrams are outside the model.
• TP exchange: the frame view shows a group data frame. Bus arbitration, priority scheduling, TP acknowledgments (ACK, NACK, BUSY), and automatic retransmissions are outside the model.
• Object flags: W, T, R, and U are modeled; C is always enabled. Initialization-read behavior is not modeled.
• Internal associations: a device may deliver its own transmitted telegram to other local objects on the same group address, subject to W. Real product behavior varies.
• Power supplies: drawn on lines and segments that declare one; main lines and the backbone are not given one, and the bus load (consumption against rated current) is not computed.
• Topology: lines 0.1 to 0.15, connected directly to the backbone, are allowed in KNX but not supported; lines belong to areas 1 to 15.
• Couplers: filter tables derive from declared associations. The routing counter starts at 6 and decreases at each modeled coupler. A repeater does not filter. Each line has at most one extension (repeater or segment coupler), connected to its main segment; see couplers and repeaters.
• KNXnet/IP: the model routes between IP routers with filter tables; it does not model tunneling that bypasses those tables.
• Supervisors: a supervisor does not automatically read states at startup. It shows values after receiving telegrams or USB interface reads.
• Shutters: the actuator estimates travel without a position sensor; the connected shutter moves at its own speed. See shutters.
• Clock: the simulated clock has no time zone and no summer time change; DPT 19.001 (date and time with quality flags) is not supported. The clock in the timers example is a push-button that simulates scheduled times; see the time schedule example for a clock master and a time switch.
• Relay feedback: it reports the controlled relay state, not a measured mains voltage.
• Scenes: scene recall (DPT 17.001) is modeled; scene storage (DPT 18.001) is not.
• DPTs: only the listed data types are simulated; passive and display devices can show other standard DPTs as raw bytes.
• Other systems: a gateway models only its KNX side; Modbus, BACnet, and M-Bus are not simulated.
• USB interface panel: group reads and writes are modeled, without programming or downloads.
• DALI: group and broadcast control are modeled, without DALI commissioning, color control, or emergency lighting. See DALI.
• Configuration warnings: parameters that compensate a property of the load (valve type, motor wiring, contact type) are compared with that property; a mismatch is simulated and shown as a warning. See the warning codes.
• Heating: each room uses a simplified thermal time constant, and heating or cooling power is assumed to be available. Operating modes use a DPT 20.102 object; forced-mode and one-bit mode objects are not modeled. The thermostat has no built-in schedule; a time switch can send mode telegrams. Fan-coil units and air-conditioning gateways are not modeled. See HVAC.
• Metering: power comes from the rated power of each load, without measurement tolerance or power factor; energy is counted with a time scale (energyTimeScale).
• Air quality: measurements are entered by the reader; there is no air or ventilation model.
• Venetian blinds: slats turn before each movement; slat angle restoration after a movement and slat limit positions are not modeled.
• Presence detector: brightness is entered by the reader; there is no light model and no constant light regulation.
• Weather station: measurements are entered by the reader; there is no weather model. Only wind and brightness thresholds are provided.
• Logic module: one-bit AND, OR, XOR, and NOT with an enable object and an optional daily time window; no delay blocks or numeric comparisons.
• Outside scope: BACnet, KNX Secure, and connection to a real bus.