NDC comm NDC-3 - Manual (Page 5)

Page 5 © 2005 Active Research Limited
General features
4 NMEA 0183 data input ports
Each NMEA 0183 input port has a priority level. This is fixed
to the logical order that matches the port numbers, i.e. port
1 has the highest priority and port 4 has the lowest.
An NMEA 0183 data combined output port
This output combines the input data into one standard
NMEA output. The NMEA inputs and output have the same
baud rate. This means that the output can only carry as
much data as one of the inputs - therefore the combined
data from all four NMEA input channels could exceed the
data carrying capacity of the NMEA output channel. The
combiner contains special software to ensure that when
the output channel is overloaded, new data of the same
type as older data, still in the buffer, will overwrite the older
sentence. This will only happen when the output load
becomes too high, and ensures that the combiner cannot
build up excess old data in the case where the output
stream is fully loaded or overloaded.
A PC compatible RS-232 bi-directional port
A PC can use the RS-232 port to read all the NMEA data
traversing through the NDC. This allows for the possibility
of a “virtual cockpit” of instruments displaying all available
data in any manner the user requires (available from a
number of manufacturers).
Technical features
High-speed micro-controller capable of 10 million
instructions per second.
Flash ROM technology that supports automatic
programming for quick and easy updates, 10,000+ erase
cycles and a 10-year Data Retention provides carefree
user configuration.
On-chip memory store allows buffering of short term
NMEA data, allowing the unit to smooth short-term peaks
in the NMEA data flow.
NMEA 0183 inputs are opto-isolated differential inputs to
fully comply with the NMEA 0183 standard specification.
This allows the inputs to work correctly with long cable runs
and in a noisy environment. Typical operating voltage is
2.0v to 15.0v. The unit can withstand +/- 35v continuously,
and +/- 40v transients. The Opto-isolator can protect any
upstream equipment (chart plotter, laptop PC, radar etc.)
from up to 2000v of common mode voltage difference.
NMEA 0183 full-differential output driver. This can drive
up to 15 fully compliant NMEA 0183 device loads, with a
30mA (maximum) drive capability. The full-differential
output ensures better quality communications and lower
noise emissions on unshielded twisted pair cabling.
Full specification RS232 interface ensures that any
marine electronic device (or PC) that has an RS-232 port
receives all the input NMEA data, and can add its own
NMEA data to the combined output. This connection also
allows the unit to be updated via the free flash upgrade
software that will be made available on the Actisense™
website if the NDC-3 software has been enhanced.
Wide battery input voltage range to offer maximum
compatibility, the NMEA 0183 NDC-3 can operate from a
battery supply anywhere between 8 and 35 volts.
Low Power Consumption that is typically 26-30mA at 12
volts and 16-18mA at 24 volts.
A diagnostic LED indicates the operation mode of the
NDC-3, if any faults have been detected, or the peak load
currently on any one of the NMEA inputs.
Very tough Polycarbonate case is certified to IP66
(classified as “totally protected against dust and protection
against low pressure jets of water from all directions”).
Being Polycarbonate, it is also incredibly strong, offering
a wide temperature range and superior protection to the
electronics inside. The IP66 rating of the case is only
limited by the sealing gasket strip, which can be enhanced
by applying a suitable non-acid based marine sealant to
the gasket after wiring and testing. This will allow use of
the unit in areas where salt spray could enter, accidental
immersion may occur, or in environments where maximum
long-term reliability is paramount.
Robust Nylon grommets are certified to IP68 (classified
as immersible for long periods without water ingress). Note
that to achieve this level of water integrity all grommets
must be occupied by round-section cables.
Large range of possible cable diameters of between
4.5 mm and 10 mm, single or multi-pair wire types can be
easily accepted.
Software updates
The NDC-3’s built-in firmware is held in “flash” memory,
allowing quick and easy upgrades using a simple Microsoft
Windows (95/98/ME/NT/2000/XP) user interface program
(Flash Centre) running on a connected PC.
It is our policy to provide these updates free on our website,
www.actisense.com , so that your combiner can become
more sophisticated with time, and should there be any
bugs reported in the software, they can be promptly fixed
without the unit coming out of commission. This upgrade
can be performed with the unit completely in-situ, via a PC
connected to the RS232 port.