Mercury 250 Jet, Руководство по установке

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250 HP JET DRIVE INSTALLATION MANUAL
Page 12 90-10240040 DECEMBER 2003
Wiring Information for CAN Type Gauges
REQUIREMENTS
SmartCraft communications are via the Controller Area Network (CAN), electrically imple-
mented on a twisted pair of wires. Note: SmartCraft harnesses include other signals besides
CAN.
The maximum distance between any two modules on the SmartCraft bus is 40 meters (130
feet). This distance is calculated as the total harness length between the modules (trunk
length plus drop lengths).
There must be exactly two termination resistors on the CAN bus.
No more than 20 modules may be connected to the bus. This is the maximum number of
connections supported by the engine control module software.
INSTALLATION GUIDELINES
SmartCraft installations should use Mercury Marine harnesses and junction boxes. This as-
sures a robust mechanical implementation as well as proper connection of all signals.
The ideal installation uses a single trunk line with short drops to individual modules. Two
termination resistors, one at each end of the trunk line, minimize signal reflections. Signal
reflections can increase radio frequency interference and the potential for bit errors on the
bus.
The trunk line is not defined by junction boxes. The trunk should be considered to be the
distance between the termination resistors. Drops may be at the ends of the trunk line or
anywhere else that is convenient for the installation. Note that the trunk line can “loop-back”
in some installations.
•
The single engine System Monitor example on page 14 illustrates a trunk line with two
drops of essentially zero length, one at the engine and the other at the gauge.
•
The single engine System Tach and Speedo example on page 14 illustrates a trunk line
with one zero length drop at the engine and two three foot drops at the gauges.