Combination Switch Reading Function
COMBINATION SWITCH READING FUNCTIONDescription
- BCM reads combination switch (wiper) status and controls related systems, such as headlamps and wipers, according to the results.
- BCM reads information of a maximum of 20 switches by combining five output terminals (OUTPUT 1-5) and five input terminals (INPUT 1-5).
Operation Description
- BCM activates transistors of output terminals (OUTPUT 1-5) periodically and allows current to flow in turn.
- If any (1 or more) switches are turned ON, circuit of output terminals (OUTPUT 1-5) and input terminals (INPUT 1-5) becomes active.
- At this time, transistors of output terminals (OUTPUT 1-5) are activated to allow current to flow. When voltage of input terminals (INPUT 1-5) corresponding to that switch changes, interface in BCM detects voltage change and BCM determines that switch is ON.
BCM - Operation Table of Combination Switches
- BCM reads operation status of combination switch using combinations shown in table.
Sample Operation: (When Wiper Switch is Turned ON)
- When wiper switch is turned ON, contact in combination switch turns ON. At this time, if OUTPUT 1 transistor is activated, BCM detects that voltage changes in INPUT 3.
- When OUTPUT 1 transistor is ON, BCM detects that voltage changes in INPUT 3 and judges that front wiper low is ON. Then BCM sends front wiper request signal (LO) to IPDM E/R using CAN communication.
- When OUTPUT 1 transistor is activated again, BCM detects that voltage changes in INPUT 3 and recognizes that wiper switch is continuously ON.
NOTE: Each OUTPUT terminal transistor is activated at 10 ms intervals. Therefore, after switch is turned ON, electrical loads are activated with time delay. This time delay is so short that it cannot be detected by human senses.
Operation Mode
Combination switch reading function has operation modes shown.
1. Normal status
- When BCM is not in sleep status, OUTPUT terminals (1-5) each turn ON-OFF every 10 ms.
2. Sleep status
- When BCM is in sleep status, transistors of OUTPUT 1 stop the output and BCM enters low current consumption mode. OUTPUT (2, 3, and 4) turn ON-OFF every 10 ms and only input from light switch system is accepted.