IFC-050
Supplementary instructions
Supplementary instructions
IFC 050
IFC 050
IFC 050IFC 050
Supplementary instructions Supplementary instructions
Signal converter for electromagnetic flowmeters
Description of Modbus interface
Description of Modbus interface
Description of Modbus interfaceDescription of Modbus interface
Electronic Revision: ER 3.0.xx
Modbus version: 1.0.xx
© KROHNE 09/2012 - 4002202601 - AD Modbus IFC 050 R01 en
CONTENTS
IFC 050
1 Important information 3
2 Technical data 4
2.1 General technical data .....................................................................................................4
2.2 Technical data of the Modbus interface (acc. to EIA standards) ..................................... 4
3 Connection in bus systems 5
4 Local configuration 6
5 Electrical connection 7
6 Modbus protocol 8
6.1 General information concerning the protocol ................................................................. 8
6.2 RTU frame format............................................................................................................. 8
6.3 Addressing........................................................................................................................ 9
6.4 Overview of supported functions...................................................................................... 9
6.5 Device identification on the Modbus interface............................................................... 10
6.6 Coil registers .................................................................................................................. 10
6.6.1 Converter controls ................................................................................................................ 10
6.6.2 Counter controls ................................................................................................................... 11
6.6.3 Start calibration functions .................................................................................................... 11
6.7 Input registers ................................................................................................................ 12
6.8 Holding registers............................................................................................................ 13
6.8.1 Counter parameters ............................................................................................................. 13
6.8.2 Process input filter and self test parameters ...................................................................... 14
6.8.3 Modbus parameters.............................................................................................................. 15
6.9 Diagnostics ..................................................................................................................... 15
6.10 Calibration procedures................................................................................................. 16
6.10.1 Zero Flow Calibration.......................................................................................................... 16
6.10.2 Conductivity Calibration...................................................................................................... 17
7 Notes 18
2
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IFC 050
IMPORTANT INFORMATION 1
The flow converter with the RS485 interface, is able to communicate with an external device (PC
or other suitable computer system) using the Modbus protocol. This option allows data exchange
between PC or computer and single or multiple devices.
The bus configuration consists of one external device as a master and one or more converters as
slaves. For bus operation the device address (menu C5.1), baudrate (menu C5.2) and settings
(menu C5.3, C5.4, C5.5 & C5.6) must be set in the signal converter.
All devices connected to the bus, must have different unique addresses but the same baud rate
and settings.
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2 TECHNICAL DATA
2.1 General technical data
Interface RS485, galvanically isolated
Baud rate 1200, 2400, 3600, 4800, 9600, 19200, 38400, 57600 or 115200
Protocol Modbus RTU (available as a separate document on request)
Maximum participants on bus 32 per line, master included (may be extended by repeaters)
Coding NRZ bit coding
Address range Modbus: 1...247
Transmission procedure Half duplex, asynchronous
Bus access Master / slave
Cable Shielded twisted pair for RS 485 applications
Distances Maximum 1.2 km / 3937 ft without repeater (dependant on
baud rate and cable specifications)
2.2 Technical data of the Modbus interface (acc. to EIA standards)
Kind of signal transmission Differential, 2-wire topology
Maximum number of
transmitter/receivers
Voltage range on converter input -7...+12 V
Maximum voltage on converter output 5V
Minimum voltage on driver output, max.
load
Maximum input current (off state) -20...+20 μA
Receiver input voltage -7...+12 V
Sensitivity of the receiver -200...+200 mV
Receiver input resistance >12kΩ
Short circuit current < 250 mA
32
U
diff
>1.5V
IFC 050
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IFC 050
CONNECTION IN BUS SYSTEMS 3
For proper operation of Modbus in half duplex mode in single or multi-drop communication, it is
recommended that a termination resistor is applied to both ends of the data line. The simplest
form of termination is line-to-line resistor across the differential input.
In RTU mode the Modus protocol requires quiet periods on the communications bus for
synchronisation. It is therefore important that the Modbus is not allowed to "float", i.e.
unreferenced to 0 V, as this could lead to spurious signals due to noise pick-up. It is therefore
necessary to employ biasing resistors at one point on the bus network, normally the "end".
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4 LOCAL CONFIGURATION
IFC 050
Converter Fct.
Display Description and settings
No.
C5.1 Slave Address Selects the Modbus address of the device.
C5.2 Baud Rate Selects the baud rate of the device.
C5.3 Parity Selects the parity.
C5.4 Data Format Selects the data format.
C5.5 Transmission Delay Selects the delay between receiving the last byte of a request and
C5.6 Stop Bits Selects the number of stop bits.
C5.7 Information Displays information about the device.
Range: 1..247 (default = 1)
Options:
1200 / 2400 / 3600 / 4800 / 9600 / 19200 (default) / 38400 / 57600 / 115200
Options:
even parity (default) / odd parity / no parity
Options:
Big Endian (default) / Little Endian
sending the first byte of the response.
Range: 0..40ms (default = 0ms)
Options:
1 (default) / 2
6
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