Circuit Description - ViewSonic E70FSB-2 - E 70F+SB - 17" CRT Display Service Manual

4. Circuit Description

4-1 MICRO CONTROLLER CIRCUIT
MICRO Controller
The IC101 contains a 8031 8-bit CPU core, 60K bytes of RAM, 16K bytes of ROM,14 channel 8 bit PWM D/A
converters, 2 channel A/D converters for key detection,0.5sec watch-dog timer, internal H-sync and V-sync
signals processor providing mode detection, watch- dog timer preventing system from abnormal operation, and an
I²C 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 Pin32 will output a 60Hz V-SYNC free run signal. The Pin33
will output a 48KHz H-SYNC free run signal. for the monitor testing use.
On Screen Display Controller
The IC801 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 (R154,
C166, R155) and filter (R175, C167) 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, I²C 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.
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