System Protocols - Raymarine e7D Installation And Operation Handbook

3.8 System protocols

Your Multifunction Display can connect to various instruments and
displays to share information and so improve the functionality of
the system. These connections may be made using a number of
different protocols. Fast and accurate data collection and transfer is
achieved by using a combination of the following data protocols:
• SeaTalk hs
• SeaTalk ng
• NMEA 2000
• SeaTalk
• NMEA 0183
Note: You may find that your system does not use all of the
connection types or instrumentation described in this section.
SeaTalk hs
SeaTalk hs is an ethernet based marine network. This high speed
protocol allows compatible equipment to communicate rapidly and
share large amounts of data.
Information shared using the SeaTalk
• Shared cartography (between compatible displays).
• Digital radar data.
• Sonar data.
Seatalk ng
SeaTalk ng (Next Generation) is an enhanced protocol for connection
of compatible marine instruments and equipment. It replaces the
older SeaTalk and SeaTalk 2
SeaTalk ng utilizes a single backbone to which compatible
instruments connect using a spur. Data and power are carried within
the backbone. Devices that have a low draw can be powered from
the network, although high current equipment will need to have a
separate power connection.
SeaTalk ng is a proprietary extension to NMEA 2000 and the proven
CAN bus technology. Compatible NMEA 2000 and SeaTalk /
SeaTalk 2 devices can also be connected using the appropriate
interfaces or adaptor cables as required.
NMEA 2000
NMEA 2000 offers significant improvements over NMEA 0183, most
notably in speed and connectivity. Up to 50 units can simultaneously
transmit and receive on a single physical bus at any one time,
with each node being physically addressable. The standard
was specifically intended to allow for a whole network of marine
electronics from any manufacturer to communicate on a common
bus via standardized message types and formats.
SeaTalk
SeaTalk is a protocol which enables compatible instruments to
connect to each other and share data.
The SeaTalk cable system is used to connect compatible
instruments and equipment. The cable carries power and data and
enables connection without the need for a central processor.
Additional instruments and functions can be added to a SeaTalk
system, simply by plugging them into the network. SeaTalk
equipment can also communicate with other non-SeaTalk equipment
via the NMEA 0183 standard, provided a suitable interface is used.
NMEA 0183
The NMEA 0183 Data Interface Standard was developed by
the National Marine Electronics Association of America. It is an
international standard to enable equipment from many different
manufacturers to be connected together and share information.
The NMEA 0183 standard carries similar information to SeaTalk.
However it has the important difference that one cable will only
carry information in one direction. For this reason NMEA 0183 is
generally used to connect a data receiver and a transmitter together,
Planning the installation
hs network includes:
protocols.
e.g. a compass sensor transmitting heading to a radar display. This
information is passed in 'sentences', each of which has a three
letter sentence identifier. It is therefore important when checking
compatibility between items that the same sentence identifiers are
used some examples of which are:
• VTG - carries Course and Speed Over Ground data.
• GLL - carries latitude and longitude.
• DBT - carries water depth.
• MWV - carries relative wind angle and wind speed data.
NMEA baud rates
The NMEA 0183 standard operates at a number of different
speeds, depending upon the particular requirement or equipment
capabilities. Typical examples are:
• 4800 baud rate. Used for general purpose communications,
including FastHeading data.
• 9600 baud rate. Used for Navtex.
• 38400 baud rate. Used for AIS and other high speed applications.
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