System Description

SYSTEM DIAGRAM 

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System Description 

OUTLINE 

• BCM reads the status of the combination switch (light, turn signal, wiper and washer) and recognizes the status of each switch.
• BCM has a combination of 5 output terminals (OUTPUT 1 - 5) and 5 input terminals (INPUT 1 - 5). It reads a maximum of 20 switch states.

COMBINATION SWITCH MATRIX 

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System	INPUT 1	INPUT 2	INPUT 3	INPUT 4	INPUT 5
OUTPUT 1	-	FR WASHER	FR WIPER LOW	TURN LH	TURN RH
OUTPUT 2	FR WIPER HI	-	FR WIPER INT	PASSING	HEADLAMP 1
OUTPUT 3	INT VOLUME 1	-	-	HEADLAMP 2	HI BEAM
OUTPUT 4	-	INT VOLUME 3	AUTO LIGHT	-	TAIL LAMP
OUTPUT 5	INT VOLUME 2	-	-	-	-

COMBINATION SWITCH READING FUNCTION 

Description 

• BCM reads the status of the combination switch at 10 ms intervals normally.

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  NOTE: BCM reads the status of the combination switch at 60 ms intervals when BCM is controlled at low power consumption control mode.
• BCM operates as follows and judges the status of the combination switch.
  • It operates the transistor on OUTPUT side in the following order: OUTPUT 1 → 2 → 3 → 4 → 5, and outputs voltage waveform.
  • The voltage waveform of OUTPUT corresponding to the formed circuit is input into the interface on INPUT side if any (1 or more) switches are ON.
  • It reads this change of the voltage as the status signal of the combination switch.

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Operation Example 

In the following operation example, the combination of the status signals of the combination switch is replaced as follows: INPUT 1 - 5 to "1 - 5" and OUTPUT 1 - 5 to "A - E".

Example 1: When a switch (TAIL LAMP) is turned ON

• The circuit between OUTPUT 4 and INPUT 5 is formed when the TAIL LAMP switch is turned ON.

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• BCM detects the combination switch status signal "5D" when the signal of OUTPUT 4 is input to INPUT 5.
• BCM judges that the TAIL LAMP switch is ON when the signal "5D" is detected.

Example 2: When some switches (TURN RH, TAIL LAMP) are turned ON

• The circuits between OUTPUT 1 and INPUT 5 and between OUTPUT 4 and INPUT 5 are formed when the TURN RH switch and TAIL LAMP switch are turned ON.

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• BCM detects the combination switch status signal "5AD" when the signals of OUTPUT 1 and OUTPUT 4 are input to INPUT 5.
• BCM judges that the TURN RH switch and TAIL LAMP switch are ON when the signal "5AD" is detected.