Power-Up Process; Clock; Input Clock; Figure 4-2 Diagram Of Clock Distribution - Hytera MD78X Service Manual

Service Manual
4.2.4

Power-up Process

Step 1 Power on the radio using one of the three methods (Power On/Off key, Ignition Signal, or
Emergency);
U917 generates reset signal and remain low level for 1.25 seconds, allowing the processor
Step 2
starts.
Step 3 Power-on signal will be sent to the processor;
After receiving the signal, the processor generates the level of PWR_CTRL. Then the power-up
Step 4
procedures are completed.
4.3

Clock

Option Board
U231
32.768KHz
4.3.1

Input Clock

The 32K clock provided by X375 is mainly used for timing and sleeping of the system. Its frequency
(32.768 kHz) is divided by U302 (32768 times in all) to 1Hz for counting seconds. The system clock
(19.2MHz) is generated by an external crystal oscillator.
U302
32K
32K_IN
VSS
CLK32K_IN
19.2MHz
9.6MHz
APLL

Figure 4-2 Diagram of Clock Distribution

DAC
9
Baseband Section
19.2MHz
U701
U100
19.2MHz