VEGA VEGABAR 87 Modbus and Levelmaster protocol - Operating Instructions - Manual (Page 62)

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10 Supplement
VEGABAR 87 • Modbus and Levelmaster protocol
46297-EN-131107
RTU Protocol
ABB Totalflow Modbus RTU, ASCII
Bristol ControlWaveMicro Modbus RTU, ASCII
Fisher ROC Modbus RTU, ASCII
ScadaPack Modbus RTU, ASCII
Thermo Electron Autopilot Modbus RTU, ASCII
Parameters for the bus communication
The VEGABAR 87 is preset with the default values:
Parameter Configurable Values Default Value
Baud Rate 1200, 2400, 4800, 9600, 19200 9600
Start Bits 1 1
Data Bits 7, 8 8
Parity None, Odd, Even None
Stop Bits 1, 2 1
Address range Modbus 1 … 255 246
Start bits and data bits cannot be modified.
General configuration of the host
The data exchange with status and variables between field device and host is carried out via
register. For this, a configuration in the host is required. Floating point numbers with short prevision
(4 bytes) according to IEEE 754 are transmitted with individually selectable order of the data bytes
(byte transmission order). This "Byte transmission order" is determined in the parameter "Format
Code". Hence the RTU knows the registers of the VEGABAR 87 which must be contacted for the
variables and status information.
Format Code Byte transmission order
0 ABCD
1 CDAB
2 DCBA
3 BADC
10.3 Modbus register
Holding Register
The Holding registers consist of 16 bit. They can be read and written. Before each command, the
address (1 byte), after each command, a CRC (2 byte) is sent.
Register Name Register Num-
ber
Type Configurable
Values
Default Value Unit
Address 200 Word 1 … 255 246 -