Sharp QD-101MM, Service Manual

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8
4. CIRCUIT DESCRIPTION
1. GENERAL
Circuit will be described in reference to the QD-101MM block diagram in Fig. 2.
Composite video signal which enters via pin jack connector is converted into the digital RGB
in the composite video input circuit by the control signal from the I
2
C bus controller. The signal
then enters the signal selector circuit.
Computer analog signal enters via the 15-pin connector and is processed through the computer
analog input circuit and the A/D conversion circuit. The signal is then converted into the digital
RGB signal and enters the signal selector circuit.
Digital video signal from IBM PC EGA or CGA enters via the 15-pin connector is input into the
signal selector circuit.
The signal selected in the signal selector circuit is written into the field memory. The writing
operation into the field memory is controlled by signals which are generated in the IC100 by
HSYNC. VSYNC. Since the LCD control is asynchronous with the computer signal, FRCK.
FRRS is generated in the IC100, and is read out at their timings.
The audio control circuit controls the audio signal input from the audio input terminal, according
to the control signal from IC100. IC400(MPU) controls IC100, IC107 (I
2
C bus controller) by the
key operation from SW PWB. Since control data from the key is stored into EEPROM, the set
data is memorized even if the power is turned off.
2. COMPUTER SIGNAL INPUT CIRCUIT
In addition to composite video signal, QD-101MM can receive the computer analog RGB signal
and the computer digital RGB signals of MDA, CGA, EGA. These signals enter each input
circuit via the 15-pin connector (J2), pin jack (CN600), and S-terminal(CN601). After they are
converted into the digital signals, they are input to the signal selector or directly to the signal
selector circuit.
Refer to MAIN CIRCUIT No.3.
2.1.Computer digital signal input circuit
The computer digital signal is input to Pins 2, 3, 4, 5, 12 and 15 of J2, and is directly sent to the
signal selector.
EGA outputs the video signal at the 6-bit TTL level. (R, G, B, r, g, b)
CGA outputs the video signal at the 4-bit TTL level. (R, G, B ,I)
MDA outputs the video signal at the 2-bit TTL level. (Mono, Video, I)
As basic, the pins of J2 output the following signals.
Table 1
x:Don`t care or N.C.
Signal
Connector J2's Pin Number
12 15 4 2 5 3 14 13 11
EGA g b r G R B Vsync Hsync GND
CGA I x x G R B Vsync Hsync GND
MDA I MONO x x x x Vsync Hsync GND