Variables andKNX™ group addresses
P.
153 of 349
Use of variables and
group addresses
in the user program of
the Enertex
®
EibPC
Telegram structure
Useful background information
Data types
Target address
Bit length
(of user data)
User data
Major gr.
Middle gr.
Subgr.
2
1
0
Values
different data types, e. g. 10°C, 10%, -2, “alarm“
number
1...112
Schematic configuration of a telegram
Figure 5: Schematic telegram structure
"Telegram" designates a complete block of data for the transmission of information. Besides the data
to be transported, the telegram contains all additionally needed information in specific fields, as
indicated in Figure 5.
Among the transported data, the bit length as well as the “interpretation“ of the data must be known,
so that a meaningful programming is possible.
For example, there are numeric types with different bit lengths: The value “1“ can be transmitted with
both 1-bit, 4-bit, 8 bits and so on. Because of this ambiguity, the so-called “data type“ must be
accurately specified in the programming.
The term “data type“ summarizes the numeric type (“interpretation“) and bit length in one unit.
In the Enertex
®
EibStudio, the following syntax has been chosen:
The data type is appended to a number or a address.
The data type mostly consists of one letter and a 2-digit number.
Possible types (based on standard programming languages) are:
●
Unsigned (positive) integers
Letter
u (“unsigned“)
●
Signed integers
Letter
s (“signed“)
●
Floating-point numbers
Letter
f (“float“)
●
Character string
Letter
c (“char“)
●
Date and time
Letter
t
or
d
or
y (“time“, “day“, “year“)
The following bit lengths are possible
●
1 bit
01
digits
●
4 bit
04
digits
●
8 bit
08
digits
●
16 bit
16
digits
●
24 bit
24
digits
●
32 bit
32
digits
●
64 bit
64
digits
●
112 bit
14
digits
●
11200 bit (1400 characters)
no digits
Accordingly,
u08
is a data type of length 8 bits and represents an unsigned (positive) integer.
HandbuchEibPC_USA-30.odt, 2017-05-11
Enertex
®
Bayern GmbH - Erlachstraße 13 - 91301 Forchheim - [email protected]