YSI IQ S ENSOR N ET Field bus linking - Manual (Page 29)

IQ S ENSOR N ET Field bus linking Communication with field buses
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* MSB = Most significant bit, LSB = Least significant bit
4.2.4 Example
Query of the sensor data
block for sensor S02
The counting method of the Modbus registers and Modbus
bits and the allocation of MSB and LSB is different from the
usual method of most programming languages.
Modbus Usually
Count start of the register 1 0
MSB* allocation of the register Bit 1 Bit 15
LSB* allocation of the register Bit 16 Bit 0
Modbus query
Byte Value Information Meaning of the value
1 01h Modbus address of
the IQ S
ENSOR N ET
01h --> 1
2 04h Function 04h --> 4
Read Input Register
see section 4.2.2
3 00h Start address HI 0008h --> 8
Start with register 9
(Modbus counting method)
4 08h Start address LO
5 00h Number of HI regis-
ters 0008h --> 8
8 registers
6 08h Number of LO regis-
ters
7 70h CRC (HI) Checksum (CRC)
8 0Eh CRC (LO)