mru SWG 100 biogas, Руководство пользователя

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MRU GmbH SWG 100 User Manual
Page 100 of 141
12. APPENDIX
12.1. Modbus via RS485 specification
General information
•
The Modbus (slave function) requires the firmware version V1.01.70 dated
17.11.2014 or later.
•
The analysers are able to work as Modbus slave using the RS232 or RS485 port
(possibly with external RS232/RS485 adapter)
•
supports RS485 interface with 2/4 wires (half/full duplex)
•
supports only the binary Modbus protocol (RTU)
•
supports Modbus command Read Holding Register (command no 3)
•
supports Modbus command Read Input Register (command no 4)
•
the slave Modbus address is user definable from 1 to 238
•
communication parameter are user definable as follows:
- 9600 baud
- 19200 baud
- even parity and 1 stop bit
- no parity and 2 stop bits
•
Multi byte values are transmitted in Motorola
®
byte order (
Big-Endian
). Only
the CRC16 at the end of each frame is transmitted in Intel
®
byte order (Little
-
Endian
).
In case you need Little-Endian byte order in the master's system:
- 16bit values (occurs only in the frame): swap bytes 0<=>1
- 32bit values (occurs only in the data): swap bytes 0<=>3 and swap bytes
1<=>2
•
All addresses written in this document are decimal (not hexa-decimal)
•
All readable data are 32bit values, therefore the analyser only accepts even
addresses end even number of registers to be read.
•
The maximal number of 32bit-values to be read with one single read command
is 63
(126 modbus registers)
•
Data types (used in table below):
U32
FL 32 bit floating point value (reads -1E38, when not available)