Gill Instruments Ltd
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MaxiMet
Page 49
Issue 1
Doc. No. 1957-PS-000x
March 2015
MaxiMet MODBUS NOTES
1.
All registers are 16bit.
2.
The first byte is high order and the second is low.
3.
Each measurement is comprised of two 16bit registers.
4.
For all registers, the order of the two data bytes comprising the 16-bit register's value shall
be: High Byte/Low Byte.
5.
For each 32-bit data type (whether floating point or integer), the order of the first pair of
bytes and last pair of bytes shall be: High Word/Low Word.
6.
Registers start at address 40001.
7.
Holding registers available in the order of the MaxiMet data string (which can be
established by the REPORT command in non-Modbus Gill ASCII Mode).
8.
If measurements cannot be computed (i.e.: a blank field in Gill mode output string), their
Holding Register contents shall be set to the Maximum Positive value (0x7FFFFFFF for
32-bit format data (both floating point and integer), and as 0x7FFF for 16-bit format data).
MaxiMet MODBUS Default Data String Field Encoding (example shows GMX600):
Node
4-byte character string
Registers 40001-2.
Direction:
32 Bit Floating point value
Registers 40003-4.
Speed:
32 Bit Floating point value
Registers 40005-6.
CDIR
32 Bit Floating point value
Registers 40007-8.
Pressure:
32 Bit Floating point value
Registers 40009-10.
Relative Humidity
32 Bit Floating point value
Registers 400011-12.
Temperature:
32 Bit Floating point value
Registers 400013-14.
Dewpoint:
32 Bit Floating point value
Registers 400015-16.
Total Precipitation:
32 Bit Floating point value
Registers 400017-18.
Precipitation Intensity: 32 Bit Floating point value
Registers 400019-20.
Date:
16 Byte Character String
Registers 400021-28.
Time:
16 Byte Character String
Registers 400029-36.
Supply Voltage:
32 Bit Floating point value
Registers 400037-38.
Status:
32 bit Unsigned Integer (UINT) Registers 400039-40.
See Simply Modbus program reading example MaxiMet MODBUS Data as follows:-
