Iiyama HA703UT, Руководство по обслуживанию

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5. CIRCUIT DESCRIPTION
5-1 MICRO CONTROLLER CIRCUIT
MICRO Controller
The IC101 contains a 6502 8-bit CPU core, 256 bytes of RAM, 16K bytes of ROM,14 channel 8 bit PWM
D/A converters, 2 channel A/D converters for key detection, one 8 bit pre-loadable base timer, internal H-
sync and V-sync signals processor providing mode detection, watch- dog timer preventing system from
abnormal operation, and an I
2
C bus interface.
H/V sync signals processor
The functions of the sync processor include polarity detection, H-SYNC & V-SYNC signals counting,
Programmable SYNC signals output, free running signal generator. Pin41/Pin42 are for the H-SYNC and
V-SYNC input, Pin34/Pin33 will output the same signal as input sync signal without delay, and the polarity
are setting in the positive. When no signal input, the Pin33 will output a 61HZ V-SYNC free run signal.
The Pin33 will output a 62.5KHz H-SYNC free run signal. for the monitor testing use.
On Screen Display Controller
The IC103 is designed for display the built-in characters or fonts onto monitor screen. The display
operation is by transforming data and control information from micro controller to RAM through a serial
data interface.
Pin2 is used to control the internal oscillator frequency by DC voltage input from external low pass filter
(R125, C114, R161) and filter (R126, C115) is used to regulate the appropriate bias current for internal
oscillator the resonate at specific dot frequency.
Pin5 is input the horizontal fly back pulse, for PLL generator tracking.
Pin6 is left floating, I
2
C bus is enabled. Otherwise the SPI bus is enabled.
Pin7 the external data transfer through this pin to internal display registers and control registers
Pin8 the clock-input pin is used to synchronize the data transfer.
Pin10 is input the vertical flyback pulse for synchronizing the vertical position.
Pin12 is output a blanking signal to cut off external R.G.B signals of VGA while this chip is displaying
characters or windows.
Pin13, Pin14, Pin15 is used to output the OSD (B.G.R) video signal.
5-2 DEFLECTION CIRCUIT
The deflection circuit is achieved by a high performance and efficient solution IC 401 (TDA4856) for this
monitor. The concept is fully DC controllable and can be used in applications with a micro-controller
solutions.
The TDA 4856 provides sync. Processing with full auto sync. capability, a flexible SMPS block and an
extensive set of geometry control facilities. Further the IC generates the drive waveforms for DC coupled
vertical boosters to the TDA 4866 [ref Page-28].
Horizontal Oscillator
The oscillator is of the relaxation type and requires a capacitor of 10nF C413 at pin 29. The maximum
oscillator frequency is determined by a resistor R426 from pin 28 to ground. A resistor R425 from pin27 to
pin28 defines the frequency range.
PLL 1 Phase Detector
The phase detector is a standard one using switched current sources. It compares the middle of H-sync. with
a fixed point on the oscillator saw-tooth voltage. The PLL loop filter C411, R424, C412 is connected to
Pin26.