SGW1-IA3-MB-NM – NMEA talker to Modbus slave Converter – User’s Manual
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Rev.4
11
4
Modbus Registers
The following table shows how to map each NMEA statement in Modbus registers.
If your NMEA talker does not send any of the statements listed here, values will be read out at
0.
Notes:
• Where two Modbus registers are indicated to represent a value of 32 bits, the first
register contains the upper part and the second the lower part of the represented value.
• Where clarifications such as "x10" are specified, it means that the value obtained from
the NMEA device is multiplied by the corresponding factor to achieve a higher degree of
resolution in the indicated value.
• Where "ASCII" is specified, it means that the value read is the numerical representation
according to the ASCII coding of the letter obtained by the device that delivers the NMEA
frame.
• Where "ddmmyyyy" is specified, it means that the value indicated for this case is 2 digits
representing the day, 2 the month and 4 the year. Thus the decimal number 05112012,
refers to the date November 5, 2012.
• Where "hhmmss" is specified, it means that the value indicated for this case is 2 digits
representing the hour, 2 minutes and 2 seconds. Thus the decimal number 123045, refers
to the time 12:30:45.
• Latitude and Longitude are mapped following this procedure.
Here’s a latitude conversion from a Modbus Register to the DDºMM’SSSSSS’’ and the GGA
NMEA sentence format
40003:4
Latitude (º x 10,000,000) = 854273798
To convert this number to the DDºMM’SSSSSS’’ format
* 854273798 / 10,000,000 =
85
.4273798
º
* 0.4273798 * 60 =
25
.6427880
’
* 0.6427880 * 60 =
38.56728”
* LAT:
85°25’38.56728’’.
To convert this number to the GGA NMEA sentence format
(DDMM,MMMMM)
* 854273798 / 10,000,000 =
85
.4273798
º
* 0.4273798 * 60 =
25.6427880’
* 85 * 100 =
8500
+ 25.642788
* LAT:
8525.264788,N
