AMX NetLinx NXB-KNX Instruction Manual download pdf (Page 21)

NetLinx Programming

NXB-KNX KNX Communications Gateway

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.

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:

Source ID - hardware address of the transmitting device

Destination Address - group addresses of receiving devices

User data

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:

A Source ID is the hardware address of the device transmitting the Telegram.

A Destination Address is a group address characterizing a function.

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.

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.

FIG. 21 Course of communication

KNX

Control

Bus

NXB-KNXNetLinx Master

AMX NXB

MOD

AMX NXB

Updater

NetLinx

Program

1 ... 20 21 22 ... 64

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AMX NetLinx NXB-KNX Instruction Manual Page 21

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