AP1.1 OVERVIEW of NMEA-0183 Ver-3.00
AP1-2
The following sentences are used: e.g) the DTM sentence is:
$ -- DTM , ccc , a , x.x , a , x.x , a , x.x , ccc *hh <CR><LF>
1) 2) 3) 4) 5)
1) “$” or “!” HEX 24 or HEX 21 – Start of sentence
2)
<address field>
TALKER identifier and sentence formatter
3) [“,”<data field>] Zero or more data fields
4) “*”<checksum field> Checksum field
5) <CR><LF> Hex 0D 0A – End of sentence
The first field shall be an address field containing the identity of the TALKER and the
sentence formatter which specifies the number of data fields in the sentence, the type of
data they contain and the order in which the data fields are transmitted. The remaining
portion of the sentence may contain zero or multiple data fields.
The maximum number of characters in a sentence shall be 82, consisting of a maximum
of 79 characters between the starting delimiter “$” or “!” and the terminating <CR>
<LF>.
A checksum field shall be transmitted in all sentences. The checksum field is the last
field in a sentence and follows the checksum delimiter character “*”.
The checksum is the 8-bit exclusive OR (no start or stop bits) of all characters in the
sentence, including “,” delimiters, between but not including the “$” and the “*”
delimiters. The hexadecimal value of the most significant and least significant 4 bits of
the result is converted to two ASCII characters (0-9, A-F (upper case)) for transmission.
The most significant character is transmitted first.
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