Mitsubishi Electric 1786FD2 Service Manual page 67

MEA 1786FD2 CRT Monitor Service Guide
MICROCONTROLLER CIRCUIT OPERATION THEORY
1. Introduction :
This model will support powerful OSD function to help end user fine adjustment. The
Microcontroller circuit can determine what mode it is by detecting the frequency of horizontal
and vertical synchronous and the polarity of horizontal synchronous, and provide DC voltages to
control the picture and save the adjusted value into the EEPROM by using the OSD, "On
Screen Display control", that means the user can get any information of the picture display or
adjust it and save the status values into the EEPROM by choosing and pressing the proper key
according to the indication of the OSD. In addition, user can press i-key to do auto-calibration.
2. Block diagram :
The major parts of Microcontroller circuit are MCU, EEPROM, OSD IC, and Auto Calibration
Module. The circuit block diagram is shown as below.
Hsync
Vsync
H-polarity
EEPROM
Preset mode
User saved mode
Reset circuit
12MHz Crystal
circuit
Control Panel
5 keys
i-key
Left,Right,Enter,Ex
MCU
(MTV112)
Detecting the
input signals
of H,Vsync &
H-polarity.
Searching for
the same saved
mode timing
with the input
signals and
get the data.
Checking if the
valid key be pressed
and do key function.
(UART) External
adjustment
function
Circuit Operation Theory
Degaussing
Blanking
SC0 - SC2
OSD IC
Display OSD
and output
SCL
PWM to video
SDA
circuit
PWM
To deflection
output
circuit
PC
RS232
auto alignment
program
HBNK
VBNK
RGB
Signal
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