MB40 & MB45 MODBUS TCP/IP Gateway
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Last 10-Minute Data
Table 14: MEM 3 LAST Modbus Register Listing
Holding Register
Address 40,000+
No. of
Registers
Type
Description
181
1 Time
Year in format YYYY
182
1 Time
Month and day in format MMDD
183
1 Time
Hour in format HH
184
1 Time
Minute and second in format MMSS
185 to 239
1 Data
Unpacked weather data. Up to 54 “pieces” of comma separated
data is sequentially unpacked and placed into holding registers.
240
1 Status Comms status for the MEM 3 LAST command. 0 = bad, 1 = good.
Weather Station Data Notes:
1.
The gateway decodes comma separated values. Once the date code has been deciphered,
the remaining data is chopped into individual numbers, treating the comma as a separator.
Each number is converted and packed into the next available holding register, up to a limit of
54 numbers.
2.
Weather Station data is internally limited to ±32760. Values beyond this range are capped to
an error code shown below.
3.
The decimal point is ignored in all cases. This could cause overflow on semantically in range
numbers such as 12345.67, and also 10000.00.
4.
Numbers larger than 32760 are displayed as the error value: 32761
5.
Numbers smaller than -32760 are displayed as the error value: 32762
6.
Weather sOVERFLOW values are displayed as error code: 32763
7.
Any other conversion failure is displayed as: 32764
8.
No arithmetic is done using floating point numbers. There is therefore no underflow error.
Functionality
Weather Station Polling Period
By default, the gateway asks for each data packet from the weather station every 2.5 seconds. The
polling period can be changed by writing to Modbus register 247. Enter your preferred polling period
as a number in tenths of seconds (i.e for 2.5 seconds enter 25).
