KROHNE BM 70A-P PROFIBUS PA DE - Manual (Page 4)

Supplementary Documentation BM 70 A, BM 70 P with PROFIBUS-PA
KROHNE Messtechnik GmbH & Co. KG · Ludwig-Krohne-Str. 5 D-47058 Duisburg 4/7
Tel.: 0203-301 309 Fax: 0203-301389 · e-mail: [email protected]
The PROFIBUS-PA is normally connected to a segment coupler which, among other things, carries out the
conversion to the PROFIBUS-DP. Here, it needs to be noted in particular that the segment coupler is normally set to
a fixed baud rate on the DP side.
Further information on the planning and operation of PROFIBUS-PA networks is to be found in the KROHNE
brochure ”PROFIBUS-PA networks”.
1.1 GSD
All available GSD files of KROHNE devices – including those of the BM 70 A/P, of course - are supplied together with
each device. The GSD contains information that is needed for project planning of the PROFIBUS-DP/PA
communication network. The relevant data files must be loaded into the project planning system/master system
before start-up of the bus system.
For example, the following applies to COMET 200 or COM PROFIBUS from Siemens:
· all GSD files (*.GSD) into the directory of the GSD files, e.g. *\GSD
· all BMP files (*.BMP) into the directory of the bit maps, e.g. *\BITMAPS
In STEP7, the GSD file is automatically copied into the respective directory with “install new GSD” (in the HW-Config
Menu: EXTRAS). After that, the bit map must be copied into the directory *\SIEMENS\STEP7\S7data\Nsbmp.
Following “catalog updating” the device can be placed in the project. This will then enable the cyclic communication
(measured values and status).
1.2 PROFIBUS-PA profile
The BM 70 A/P supports the PROFIBUS-PA profile Version 2.0. Additionally, all parameters in the device are offered
via the PROFIBUS-PA interface. Within the BM 70 A/P, the following blocks are included:
· Two Function Blocks (FB) Analog Input (AI) plus Volume:
Level (default unit “m”) - Function Block AI
Distance (default unit „m“) - Function Block AI
Volume (default unit „m 3 “) - as cyclic value
Changing the unit
A change of the unit can be done only via the PROFIBUS by an operating tool. The units for level and distance
are realised according to the Profile 2.0. It can be changed via an operating tool which supports Profile 2.0.
The volume unit can be changed via the acyclic parameter in Slot 1, Index 175. Therefore an operating tool
which supports slot and index addressing is needed. Another possibility is to use the PDM tool from Siemens
because the BM 70 A/P has been integrated completely.
Volume table
The volume table is being used to calculate the volume by using the level plus a conversion table called volume
table. This volume table has to be integrated into the BM 70 A/P. The calculated volume value is available as a
cyclic value plus status. The volume table can be written to the device only by KROHNE because PROFIBUS
doesn´t support this feature at the moment.
· One transducer block for Level
This block provides the parameters defined in Profile 2.0.
· One physical block
This block contains the parameters defined in Profile 2.0, and also all device-specific parameters in the form of
an appendix.
1.3 Meaning of measurement and status information
During integration of the KROHNE device into the PROFIBUS master you can choose which values should be
transferred via PROFIBUS. This can be done by using the GSD file. Each value which is a 4 Byte Float Format
according IEEE Standard 754 Short Real Number a status byte follows. That means each measurement value
consists of 4 byte value plus 1 byte status. Other measurement values will directly follow as 5 Byte package if
configured during integration. Below the meaning of the float format and the status byte is described:
Float Format
Byte n Byte n+1 Byte n+2 Byte n+3
Bit7 Bit6 Bit7 Bit6 Bit7 Bit7
VZ 2 7 2 6 2 5 2 4 2 3 2 2 2 1 2 0 2 -1 2 -2 2 -3 2 -4 2 -5 2 -6 2 -7 2 -8 2 -9 2 -10 2 -11 2 -12 2 -13 2 -14 2 -15 2 -16 2 -17 2 -18 2 -19 2 -20 2 -21 2 -22 2 -23
Exponent Mantissa Mantissa Mantissa
Example:
40 F0 00 00 (hex) = 0100 0000 1111 0000 0000 0000 0000 0000 (binary)