
2. System clock circuit
(1) System clock circuit is shown in the figure 3.2.1.2:
Figure 3.2.1.2 System clock circuit
(2) Working principle: this clock circuit is mainly composed of X101, C104 and C103, in which X101
is a 12MHZ crystal oscillator; C104 and C103 are externally-connected resonance capacitors to produce
a 12MHZ clock signal to provide for MST718 to generate clock signal required by system through
internal doubling circuit to act as working clock.
3. System control principle
(1) System control schematic diagram is shown in the figure 3.2.1.3:
power control circuit
STV8216
PANEL_ON
control circuit
Inverter components
Remote control board
Reset circuit
Key-press board
KEY1~KEY5
RESET
IR
INVERTER ON/OFF
PANEL_ON
8216_RST
STBY
S
D
A
R
X
S
C
L
T
X
MST718
MCU
SCART JACK
DVSTB
Figure 3.2.1.3 System control schematic diagram
MST718
120
121
DVSCK
DVSDA
MT1389HD
F
B
S
S
U104
PS25LV010
W
P
S
P
IC
K
S
P
ID
I
S
P
ID
O
S
P
IC
Z
T4094
VSDA
VSCK
Serial/parallel converter
U102
Cd4094
U107
Cd4052
Mute control circuit
U109/CD4053
ASW
DVB/TV
ANT-POW
Tuner power control circuit
AMP_STB
TDA7266 audio amplifying
SEL_I/P
LCD_TFT
Vs1
Vs2
MUTE
ONMUTE
Audio input selection
- 19 -