Bus Communication - Mitsubishi Eclipse Technical Information Manual

Bus Communication

For communication to occur, the following basics
are needed:
parallel to all modules.
Bus+ and Bus- wires are biased to approxi-
l
mately 2.5 volts.
Bus+ and Bus- wires must have at least one
l
point of termination.
When the bus circuits are not allowing current to
flow, there is a "1" condition. When the bus is idle
and no messages are being sent, the bus is in the
"1" condition.
When the current source passes a small amount
of current into the Bus+ wire, and the current sink
allows a small amount of current to be passed to
ground, there is a "0" condition.
ENGINE <NON-TURBO> - Control System
ON
2.52
Bus+ ; 1 2.49 j
Voltage
Bus- I I 2.51
I
2.48
Binary 1 0
F U
Communication is based on voltage differential be-
tween the two bus wires. The differential occurs
when two parts of the communication chip, the cur-
rent sink and the current source, are used by the
communication chip to control the bus current flow.
Two different signal conditions can exist when the
bus functions normally; there can be a "0" bit or
a "1" bit.
OFF ON
2.52
2.48
1 0
0 0 8
Messages are made from a series of these "0" and
ery ten or more milliseconds.
Each microprocessor on the bus is connected to
a communication chip. The communication chip
communicates to the CPU the messages transmitted
and received on the bus.
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