General Data Formats - Siemens SENTRON VL Series System Manual

Data library
8.7 Formats
8.7.2

General data formats

Many data points have a data length of more than one byte. In this case, the numbers can
be stored either in Little-Endian- format (Intel) or in Big-Endian- format (Motorola) depending
on the processor type for which the format has been developed. In Big-Endian format, the
higher-order byte is before the lower-order byte to facilitate reading, and with Intel, the bytes
are in the opposite order.
The table below shows the standard formats used, with their value ranges and purposes.
Table 8- 39
unsigned int
unsigned char
unsigned long
In general, all data communicated over PROFIBUS is transferred in the Motorola
(Big-Endian) format.
Format "unsigned int"
The format "unsigned int" is used primarily for transferring parameters and measured values,
as well as statistical information. If the value range is insufficient, scaling is used.
To transfer measured values that can also be negative (e.g. power factors), the format
"signed int" is used.
Format "unsigned char"
If the value range of a parameter or measured value is severely restricted (e.g. phase
unbalance of 0 to 50%), the data type "unsigned char" is sufficient.
Text elements consisting of ASCII characters are assembled using the data type "char".
Format "unsigned long"
If the value range is insufficient, the data type "unsigned long" is fallen back on. This is used,
for example, with the runtime meter. If "unsigned int" were to be used for this, the runtime
meter would overflow after seven-and-a-half years.
254
Standard data formats
Format Length in byte
2
signed int 2
1
char 1
4
Signs Value range
unscaled
— 0 ... 65535
✓ – 32678 ... 32767
— 0 ... 255
— 0 ... 255
— 0 ... 4294967295
3WL/3VL circuit breakers with communication capability - PROFIBUS
System Manual, 03/2011, A5E01051353-02
Used for ...
Measured values,
parameters, etc.
Negative measured
values
Measured values,
parameters with lower
value range
ASCII characters
Measured values and
maintenance
information with a
large measuring range