PROFIBUS Communication
3/11
WL Circuit Breaker
Pre-Assignment of the Three
Basic Types
Once a basic type has been selected
with the PROFIBUS-DP master
configuration tool, the configured
slave is requested by the master to
communicate in the set basic type
at start-up.
Each WL circuit breaker can be
configured individually with a
different basic type.
Selecting the basic type first
defines the quantity of data and,
therefore, the length of the message.
The key circuit breaker data can now
be transmitted without the need to
make any additional settings. The
status of the circuit breaker is the
same for all three basic types. This
information field is 2 bytes in size
and will be explained in more detail
later. In line with the status field,
the basic types comprise between
4 and 14 data blocks, which are
pre-assigned.
The format for all the pre-assigned
measured values is a one-word
integer
. This must be interpreted
in
Motorola
format, which can be
regarded as the “standard” of the
PROFIBUS-DP.
Basic type 1
In line with the 2-byte status
information, basic type 1 comprises
four data blocks. These are pre-
assigned in such a way that they
are designed for use with a WL
circuit breaker without the Metering
Function. The most important phase
currents are transmitted here. This
pre-assignment can be changed if
necessary.
The content can be reconfigured or
the default values changed using the
BDA.
Basic Type 2
Basic type 2 comprises 8 data blocks,
which are pre-assigned for a WL
breaker with the Metering Function.
Not all of the voltages are transmitted
in full, only the main values are
transmitted, which is sufficient in
most cases.
Basic Type 3
With basic type 3, the 14 data blocks
are assigned measured values. This
basic type has also been pre-assigned
in such a way that it is only practical
to use it with the WL with a metering
function if the pre-assigned values
are not modified. As described above,
however, basic type 3 can be selected
and the pre-assigned measured
values that are not available (e.g.
phase-to-phase voltage) can be
replaced by maintenance or
parameter data as required. The
pre-assigned data can be replaced
with any information that is no more
than 2 bytes long. All the other
values are ”cast,” or, truncated and
adapted so that only the 2 least
significant bytes are transmitted.
Property Byte (PB)
In each of the basic types, the
assigned data blocks are followed
by the accompanying property
bytes. Each data block has its own
property byte.
The property byte provides additional
information on the accompanying
data block. Although it does not
have to be analyzed, it may contain
important information for the
application. A property byte is also
available for each data point in the
DPV1 data records. If the content of
one or more data blocks in the cyclic
message is replaced, the property
byte is adapted automatically.
Property bytes can be used to
determine whether a value is
available.
Definition of the Property Byte
Value
Data point is ...
0x
씲
0
Read and writable
0x
씲
1
Read only, but can be reset (e.g. maintenance)
0x
씲
2
Read only, writable in factory only
0x
씲
3
Read only
0x 0
씲
Not available
0x 4
씲
Available, but option deactivated
0x 5
씲
Available, but option deactivated and outside the area
0x 6
씲
Available and activated, but outside the area
0x 7
씲
Available, activated, within the area, and valid
Less significant
nibble
More significant
nibble
Table
3-7
The property byte describes the properties of the accompanying data point.
WL PROFIBUS Communication and Electronic Accessories • July 2004
