About The Nmea Telegram Format; Dbs Depth Below Surface - Simrad ES70 - INSTALLATION REV A Installation Manual

About the NMEA telegram format

The Simrad ES70 can send and receive information to and from several different
peripherals. All transmissions take place as telegrams with data sentences. Each
telegram has a defined format and length.
The standard is the most common protocol used to receive and transmit data
NMEA 0183
to and from peripheral sensors. A parametric sentence structure is used for all NMEA
data. The sentence start with a "$" delimiter, and represent the majority of approved
sentences defined by the standard. This sentence structure, with delimited and defined
data files, is the preferred method for conveying information.
The following provides a summary explanation of the approved parametric sentence
structure.
$aaccc,c—c*hh<CR><LF>
For more information about the NMEA standard, the format and the data sentences, refer
to their official publications. Their document NMEA 1083 - Standard for interfacing
marine electronic devices explains the formats in detail. The document can be obtained
from http://www.nmea.org.
Note
In some telegrams received from other Simrad equipments, the $ character is replaced by
the @ character. The checksum field may then not be in use.
: Start of sentence (Hex: 24).
1
"$"
2 : Address field. The first two characters (
aaccc
the last three characters are the Sentence formatter mnemonic code identifying the
data type and the string format of the successive fields.
3 : Field delimiter (Hex: 2C). 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.
: Data sentence block. This is a series of data fields containing all the data to be
4
c—c
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 : Checksum delimiter (Hex: 2A). This delimiter follows the last field of the
"*"
sentence, and indicates that the following two alphanumerical characters contain
the checksum.
6 : Checksum
hh
7 : Terminates sentence
<CR><LF>

DBS Depth below surface

This telegram contains vessel heading in degrees magnetic. The telegram is no longer
recommended for use in new designs.
It is often replaced by the
343522/A
telegram.
DPT
Telegram formats
) identifies the Talker ID, while
aa
161