Notes On Line Couplers; User Data (Dpt) Specifications And Requirements - AMX NetLinx Interface NXB-KNX Operation/Reference Manual

Notes on Line Couplers

Telegrams must be intelligently sent across KNX lines by line couplers.

User Data (DPT) Specifications and Requirements

KNX defines the User data in different Telegrams as Data Point Types (or "DPT"s)
KNX defines DPT IDs numerically, in the form major.minor (for example: DPT 1.001 or DPT 1.002), where
the major ID is designated a data length in bits or bytes (8-bit octets), and the minor ID defines format and
encoding.
The same data length may be reused in several DPT major IDs. For example, DPT 5s and DPT 6s are
1-Byte in data length, while DPT 7s, DPT 8s and DPT 9s are 2-Bytes in data length.
In essence, the NXB-KNX supports User Data (DPTs) simply in terms of data length, thereby supporting most
DPTs.
The supported data lengths are:
The module application is responsible for interpreting User Data per each KNX device's definitions.
The NXB-KNX recognizes the most commonly used User Data formats, and translates User Data to simplify
most module application responsibilities.
The supported User Data format options are:
The NXB-KNX supports the following commonly used DPT (User Data) data lengths:
Supported DPT Data Lengths
Data Length
• 1-bit
• 2-bit
• 4-bit (or "Dim4") DPT 3s "3-bit controlled" (used as on/off with dimmer step values)
• 1-Byte
• 2-Byte
• 3-Byte
• 4-Byte
• 14-Byte
NXB-KNX Operation/Reference Guide
Line couplers prevent Telegrams within a line from adding traffic load outside its line.
Line couplers also filter out cross-line Telegrams if its line is not the destination line.
Bits Bytes
• 1-bit • 1-Byte (=8-bits/octet)
• 2-bit • 2-Byte
• 4-bit • 3-Byte
• 4-Byte
• 14-Byte Text, HexText
6-bit data length DPTs are defined in KNX, but are not widely used. In practice, 1-Byte data lengths
replace 6-bit definitions, and are typically used by KNX devices.
The KNX-defined 8-Byte data length is "date time", but KNX devices typically use 3-Byte DPT 10
"time" and 3-Byte DPT 11 "date" for economy (relative to the lengthier 8-Byte combined format)
and for more flexible use.
• EIS5
• Date
• Time
Description / Example
DPT 1s are Boolean (switch)
DPT 2s "1-bit controlled" (control)
DPT 5s "8-bit unsigned" (also DPT 4s, DPT 6s, DPT 200s, DPT 201s)
DPT 9s "2-octet float" (also DPT 7s, DPT 8s)
DPT 10s "time", and DPT 11s "date"
DPT 12s, DPT 13s, DPT 14s, DPT 15s "4-octet" (e.g. counter values)
DPT 16s "String" (also known as 'Text', 'HexText')
NetLinx Programming
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