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GEN
INFO
FEATURES
COMPONENTS
ECU (Electronic Control Unit)
The ECU is mounted underneath the seat. The main functions of the ECU are ignition control, fuel
control, self-diagnosis, and load control.
• ECU’s internal construction and functions
The main components and functions of the ECU can be broadly divided into the following four
items:
A. Power supply circuit
The power supply circuit obtains power from the battery (12 V) to supply the power (5 V) that is
required for operating the ECU.
B. Input interface circuits
The input interface circuits convert the signals output by all the sensors into digital signals,
which can be processed by the CPU, and input them into the CPU.
C. CPU (Central Processing Unit)
The CPU determines the condition of the sensors in accordance with the level of the signal that
is output by the respective sensor. Then, the signals are temporarily stored on the RAM in the
CPU. Based on those stored signals and the basic processing program on the ROM, the CPU
calculates the fuel injection duration, injection timing, and ignition timing, and then sends con-
trol commands to the respective output interface circuits.
D. Output interface circuits
The output interface circuits convert the control signals output by the CPU into actuating sig-
nals for the respective actuators in order to actuate them. They also output commands to the
indicator and relay output circuits as needed.
Battery
Power
supply
circuit
ECU
Output
interface circuit
Input
interface circuit
CPU
RAM/ROM
MEMORY
Waveform
shaping circuit
Waveform
shaping circuit
Digital input circuit
A/D converter
input circuit
Injector drive
output circuit
Ignition output circuit
Relay drive
output circuit
Hall sensor
signal
(for cylinder
identification)
Pickup coil signal
(for identifying the
crankshaft position)
Switches
Sensors
Injector
Ignition coil
Relay
Communication
interface circuit
Serial comunication
circuit
Meter unit