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Simrad TV80 Reference Manual
The NMEA 0183 Interface Standard defines electrical signal requirements, data
transmission protocol and time, and specific sentence formats for a 4800 baud serial
data bus. Each bus may have only one talker but many listeners.
National Marine Electronics Association
For more information about the National Marine Electronics Association and the NMEA
0183 standard, refer to the organization's web site at:
•
http://www.nmea.org
NMEA sentence structure
A defines sentence structure is defined by NMEA to establish the communication between
two units. Most other datagram formats are designed using the same, or a similar, structure.
The following provides a summary explanation of the approved parametric sentence
structure.
$aaccc,c-c*hh<CR><LF>
1
"$"
This character (Hex: 24) is used to identify the start of the sentence.
2
"aaccc"
This is the address field. The first two characters (aa) identifies the talker ID, while the
last three characters are the sentence formatter mnemonic code identifying the data
type and the string format of the successive fields.
3
","
The comma (Hex: 2C) is used as field delimiter. This character starts each field except
the address and checksum fields. If it is followed by a null field, it is all that remains
to indicate no data in the field.
4
"c-c"
This is the data sentence block. This is a series of data fields containing all the data to
be transmitted. The data field sentence is fixed and identified by the sentence formatter
in the address field. Data fields may be of variable lengths, and they are preceded by
the field delimiter.
5
"*"
This character (Hex: 2A) is the checksum delimiter. This delimiter follows the last
field of the sentence, and indicates that the following two alphanumerical characters
contain the checksum.
274
406388/B
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