KROHNE BM 70 M User Manual
Page 49
BM 70 M
49
8.6.9 Communication
interfaces
Fct. 3.3.5 BAUDRATE
•
This function defines the transmission rate for RS 485 Communication.
- 1200 Bd.
- 2400 Bd.
- 4800 Bd.
- 9600 Bd.
- 19200 Bd.
- 38400 Bd.
•
Default value = 19200 bauds
•
For devices with PROFIBUS-PA (Ex-i) output the value has been set to 31250 bauds. and
cannot be changed.
•
The value set here is not relevant for digital Communication via the current output (e.g.
HART
®
). For this, 1200 bauds are on principle processed, independent of the setting in Fct.
3.3.5!
Fct. 3.3.6 ADDRESS
•
This function is used for entering valid addresses from 0 to 255 (PROFIBUS: 0 to 126).
•
If several devices are operated on one digital bus or via HART
®
-Multidrop, each device must
be set to an individual address under which it can then be addressed in the bus.
•
The default value is the address "0".
Fct. 3.3.7 PROTOCOL
The following Communications protocols are available:
HART
®
:
The HART
®
protocol is a Communications protocol of the "HART
®
Communication Foundation".
In addition to the "universal commands" and "common practice commands" there are "device-
specific commands" for access to all parameters and functions of the BM 70 M. In addition there
is the "device description" (DD) for BM 70 M, which can be used for universal HART
®
control
units, such as the HART
®
Communicator or SIPROM.
The standard hardware platform for HART
®
is the current output 4-20 mA with superimposed FSK
signals. For HART
®
-Multidrop (max. 15 devices on one bus), the version with Ex-i current output,
set to a constant 4 mA (Fct. 3.3.1 = OFF) should be selected.
KROHNE/PC (KROHNE protocol):
The standard Communications protocol between the
BM 70 M and the evaluation system is the standardised KROHNE protocol, which allows all
dynamic values and setting parameters to be read and changed. If the BM 70 M is connected to
existing user systems, this protocol must be applied to such systems. The protocol can also be
used when the BM 70 M is connected to the KROHNE Tank Inventory System. For further
information, please ask for the "BM 70 PC Communication" description.
MODBUS:
(not yet included in V. 3.00/3.01/4.00)
The Modbus protocol constitutes a quasi-standard for linking to programmable logic controls
(PLC) and other systems. The BM 70 M uses the Modbus RTU Protocol with extended facilities to
permit access to all dynamic
values and setting parameters. For further information, please ask for the "BM 70 Modbus"
description.