Siemens SENTRON VL Series System Manual page 139

Basic type 1
According to the 2-byte status information, basic type 1 consists of 4 data blocks. These are
pre-assigned in such a way that they are suitable above all for use with a SENTRON VL and
a SENTRON WL without metering function. The most important currents of the phases are
transferred. This pre-assignment can be changed. It is not practical to transfer the current in
the neutral conductor in the case of a 3-pole SENTRON VL. Instead, another value from the
data library can be transferred there, such as the number of switching cycles. This value is
transferred in the cyclic message frame in the position of the fourth data block instead of the
current in the neutral conductor.
Basic type 1 is suitable above all for the SENTRON VL and/or the SENTRON WL without
metering function.
Basic type 2
Basic type 2 has 8 data blocks that for a SENTRON WL are pre-assigned with a metering
function. However, not all voltages are transferred in detail. Only their mean values are
transferred and in most cases this is sufficient.
Basic type 3
Basic type 3 has 14 data blocks that are pre-assigned measured values. These are pre-
assigned in such a way that unmodified use is only meaningful with a SENTRON WL with
metering function. However, as already described, it is possible to select basic type 3 and to
replace the pre-assigned, unavailable measured values (e.g. phase-to-phase voltage) with
suitable maintenance data or parameter data. All information with a maximum length of 2
bytes can be used to replace the pre-assigned data. All other values are "cast", that is,
truncated and adapted so that only the 2 least-significant bytes are transferred.
Property byte (PB)
In each of the basic types, the assigned data blocks are followed by their associated
property bytes. Each data block has its own property byte.
The property byte is information additional to the associated data block and describes the
properties of the associated data point.
This does not have to be evaluated but it may contain important information for the
application. A property byte is also available for every data point in the DPV1 data sets. If the
content of one or more data blocks of the cyclic message frame is replaced, the property
byte adapts automatically.
The property byte can be used, for example, to determine whether or not a value is
available. When using a SENTRON VL with the standard assignment of basic type 2, the
voltage values are designated "not available". This allows the structuring of a standard
interface in an HMI (operator control and monitoring system) system that shows or hides the
field dependent on this bit. Measured values are always "read only", but some maintenance
information is "read only, but can be reset". Parameters are "read/write" or "read only"
depending on the source (e.g. ETU).
All this information can be determined from the property byte.
3WL/3VL circuit breakers with communication capability - PROFIBUS
System Manual, 03/2011, A5E01051353-02
PROFIBUS data transfer
6.9 Cyclic data traffic
139