Curcit Description - ViewSonic P95f+-1 Service Manual

19” digital controlled color monitor

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Table Of Contents

Table of Contents

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

timer, internal H-sync and V-sync signals processor providing mode detection, watch- dog timer

preventing system from abnormal operation, and an I

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, and composite sync

separation Pin41/Pin42 are for the H-SYNC and V-SYNC input, Pin33/Pin34 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 Pin34 will output a 62.5KHz

H-SYNC free run signal. for the monitor testing use.

On Screen Display Controller

The IC802 on video board 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 (R830, C817, R833) and filter (R832, C818) 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

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 IC401 (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 4887PS

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 form 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.

PLL2 Phase Detector

This phase detector is similar to the PLL1 detector and compares the line flyback pulse at pin 1

with the oscillator saw-tooth voltage. The PLL2 detector thus compensates for the delay in the

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