Netlinx Programming; Overview; Understanding The Knx Bus - AMX NetLinx Interface NXB-KNX Operation/Reference Manual

NetLinx Programming

Overview

It is important to understand that the NXB-KNX cannot configure a KNX system. The NXB-KNX serves a
functioning KNX system, and can only access bus elements with permitted use.
For a successful connection to a KNX system, expert KNX knowledge and access to
a knowledgeable KNX installer is crucial.
A wrongly set reading flag in an actuator or restrictively programmed line coupler are
difficult to find without the right analysis tools.

Understanding the KNX Bus

KNX is a bus system: all components are connected to the same line and share the available bandwidth. The
KNX bus is a 2-core wire, providing 24V power as well as data transfer between devices.
In contrast to AMX, the KNX system is organized peripherally - there is no "Master" or "Central Controller"
controlling communication. Rather, every device may transmit data to any other device. The KNX protocol
ensures that only one device transmits at a time, to avoid collisions as much as possible.
All communication is carried out via "Telegrams". A Telegram is a data package consisting of the following
components:
A Telegram can be transmitted to several Destination Addresses simultaneously (for instance to switch off all
lights in a room at the same time). There is a basic difference between Source IDs and Destination Addresses:
Thus each device connected to KNX has exactly one Source ID, but may have several Destination Addresses.
Furthermore, it is common for several Source IDs (devices) to respond to the same Destination Address.
The KNX installer assigns both address types - the Source IDs describing the type and number of utilized
devices (assigned during planning and installation).
Hardware addresses are irrelevant to the NXB-KNX. Destination Addresses are important for AMX
programmers, since they define the functions a KNX installation can perform. Functions are actuated by
transmitting a certain value to a Destination Address.
The diagram in FIG. 21 gives a graphic overview to the course of communication from the project-oriented
Netlinx source code to the NXB-KNX.
FIG. 21
Course of communication
NXB-KNX Operation/Reference Guide
Source ID - hardware address of the transmitting device
Destination Address - group addresses of receiving devices
User data
A Source ID is the hardware address of the device transmitting the Telegram.
A Destination Address is a group address characterizing a function.
NetLinx Master
AMX NXB
MOD
NetLinx
Program
AMX NXB
Updater
NetLinx Programming
NXB-KNX
Control
KNX
Bus
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