Acer 7299sl, Руководство по обслуживанию

Страница: 49 / 80

Circuit Operation Theory API Confidential
No Copy/Reproduction Allowed
2-15
MCU (MTV112)
Hsync
Vsync
H-polarity
Preset mode data,
User saved mode data.
Searching for
the same saved
mode timing
with the input
signals and
get the data.
Detecting the
input signals
of H,Vsync &
H-polarity.
Control Panel
5 keys input
i-key
Left,Right,Enter,Exit
Checking if the
valid key be pressed
and do key function.
Degaussing
Blanking
SC0 - SC2
PWM
output
OSD IC
Display OSD
and output
PWM to video
circuit
To deflection
circuit
(UART) External
adjustment
function
PC
RS232
auto alignment
program
EEPROM
Reset circuit
12MHz Crystal
circuit
Auto
Calibration
Module
DCLK
DATA
HBNK
VBNK
RGB
Signal
AP3113
2.2.3 MCU and the peripheral circuit operation theory
2.2.3.1 MCU function
The MCU is MTV112, it is an 87C51 with PWM output controlled microcontroller, after power
on,the reset circuit output a "High" to "Low" signal(>40mS) and the 12MHz crystal oscillated
circuit working , the MCU begin to manages the following functions,
(1) To detect mode and output proper SC0, SC1 and SC2 to deflection circuit.
(3) To check if there is the same saved mode in the EEPROM and get the data to transfer into
DC voltages by PWM output and RC filter circuits to control the picture, color, contrast and
brightness.
(3) To check if there is the valid key be pressed and do the key function.
(4) To memorize mode timings and any adjustable parameters of the picture into EEPROM.
(5) To output data to OSD IC for making an "on screen display control" menu.
(6) The inner registers and PWM output of MCU can be controlled by the external PC alignment
program.
(7) To calibrate the size, position, and geometry of the picture by pressing i-key. It will be placed
right size and position.
2.2.3.2 How to detect mode timing
Only when the mode timing input is stable, we can adjust the picture and check the horizontal and
vertical sync frequency by the OSD menu, and the mode timing input mean the horizontal sync
signal and the vertical sync signal.
(1) The vertical sync frequency measurement:
We use the base timer, it can generate a count during a fixed time, this fixed time is
12/12MHz and we call it "Time_base", so when the first vertical sync generated, we enable
the base timer,and the next vertical sync generated,we disable the base timer,and we only
need to calculate how many counts are during a vertical sync period. The formula is
Vertical sync frequency
= FV
= 1 / Vertical sync period
= 1 / [ Counts * (Time_base)]
==>
Vertical sync frequency = 1000000 / Counts
(2) The horizontal sync frequency measurement:
We use the event counter for calculating how many counts are during a long fixed time,
because the vertical sync period is longer than the horizontal sync period, we can enable the
event counter when the first vertical sync generated and disable the event counter when the
next vertical sync generated, this time,we can get the horizontal sync counts during a vertical
sync period.
The formula is Horizontal sync frequency