IFC-100
Signal converter for electromagnetic flowmeters
Description of Modbus interface
Description of Modbus interfaceDescription of Modbus interface
Description of Modbus interface
Electronic Revision: ER 3.0.xx
Modbus version: 1.0.xx
IFC 100
IFC 100IFC 100
IFC 100
Supplementary instructions
Supplementary instructionsSupplementary instructions
Supplementary instructions
© KROHNE 08/2014 - 4001410101 - AD Modbus IFC 100 R01 en
CONTENTS
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IFC 100
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.............................................................................................................. 16
6.9 Diagnostics ..................................................................................................................... 16
6.10 Calibration procedures................................................................................................. 17
6.10.1 Zero Flow Calibration.......................................................................................................... 17
6.10.2 Coil Temperature Calibration ............................................................................................. 18
6.10.3 Conductivity Calibration...................................................................................................... 19
IMPORTANT INFORMATION 1
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IFC 100
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The flow converter with the RS485 interface card fitted, 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 C5.8.1), baudrate (menu C5.8.2) and settings
(menu C5.8.3, C5.8.4, C5.8.5 & C5.8.6) must be set in the converter.
All devices connected to the bus, must have different unique addresses but the same baud rate
and settings.
2 TECHNICAL DATA
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IFC 100
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2.1 General technical data
2.2 Technical data of the Modbus interface (acc. to EIA standards)
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)
Kind of signal transmission Differential, 2-wire topology
Maximum number of
transmitter/receivers
32
Voltage range on converter input -7...+12 V
Maximum voltage on converter output 5V
Minimum voltage on driver output, max.
load
U
diff
>1.5V
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
Termination / polarization resistors
(refer to chapter "Electrical connection")
120 Ω / 560 Ω
CONNECTION IN BUS SYSTEMS 3
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IFC 100
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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".
4 LOCAL CONFIGURATION
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IFC 100
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Converter Fct.
No.
Display Description and settings
C5.8.1 Slave Address Selects the Modbus address of the device.
Range: 1..247 (default = 1)
C5.8.2 Baud Rate Selects the baud rate of the device.
Options:
1200 / 2400 / 3600 / 4800 / 9600 / 19200 (default) / 38400 / 57600 / 115200
C5.8.3 Parity Selects the parity.
Options:
Even (default) / Odd / No
C5.8.4 Data Format Selects the data format.
Options:
Big Endian (default) / Little Endian
C5.8.5 Transmission Delay Selects the delay between receiving the last byte of a request and
sending the first byte of the response.
Range: 0..40ms (default = 0ms)
C5.8.6 Stop Bits Selects the number of stop bits.
Options:
1 (default) / 2
C5.8.7 Information Displays information about the device.
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