Service Manual
10
7.2 Power On/Off
The mobile radio can be powered on/off through any of the following methods:
1) Power On/Off key
2) Ignition Signal
3) Emergency
7.2.1 Power On/Off Key
Power on the radio: As the Power On/Off Key is pressed, R944 becomes grounded and Q910 is on.
Then Q905 outputs high-level signal, causing U902 and Q920 to start working. Afterwards the processor
U302 executes user routines to maintain a high-level power control signal (PWR_CTR). In this case, the
radio starts to work properly after the Power On/Off Key is released. Power off the radio: As the Power
On/Off Key is pressed, LQ910 is on and a low-level signal (PWB) to turn off the radio is detected by
U302, which then controls PWR_CTRL to output low level. Afterwards, the radio becomes off.
7.2.2 Ignition Signal
When the voltage of ignition signal exceeds 7V, Q1 will be turned on by C933, R955 and R956. As a
result, the PNP transistor of Q905 will be further turned on to supply power. Meanwhile, Q401 will also be
turned on, and U302 will identify ignition signals by detecting the signal from Q401; afterwards, the level
PWR_CTRL is generated by the processor.
7.2.3 Emergency
When the emergency alarm pin is at low level, R940 is grounded, and Q906 is turned on to supply power.
Meanwhile, Q908 is also turned on. When low level is detected from Q908 but the radio is powered off,
U302 will output the level PWR_CTRL and send emergency signal. If the radio is powered on then, U302
will only output emergency signal.
7.2.4 Power-up Sequence
1) Power on the radio using one of the three methods (Power On/Off key, Ignition Signal, or
Emergency);
2) U917 generates reset signal and remains low level for 1.25 seconds, allowing the processor to
start;
3) Power-on signal will be sent to the processor;
4) After receiving the signal, the processor generates the level of PWR_CTRL. Then the power-up
To Next Page
Loading...
Need help?
General
