Description Of Qb Board Circuit Operations; Input A Input; Ddc Memory; Input A Mouse Driver - Sony VPL-PX20 Service Manual

3-7. Description of QB Board Circuit Operations

The QB board is composed of the INPUT A input terminal, DDC memory, INPUT A mouse driver, and
USB terminal.

3-7-1. INPUT A Input

Three signals are input to INPUT A; analog signal of DSUB15 pin, analog signal of 5 BNC, and digital
signal. These signals are switched by SW1201. The analog signal of DSUB15 pin is input from CN1202
and output from CN1203 to the QA board. (An input terminal is provided for the 5BNC analog signal and
digital signal in the BB board. These signals are output from this input terminal to the QA board.)

3-7-2. DDC Memory

IC1202 is a DDC memory for INPUT A. This IC is written with EDID data for DDC. When a computer
is connected to CN1202, power is supplied to the IC. If the computer connected is DDC compatible, DDC
communication is performed.

3-7-3. INPUT A Mouse Driver

IC1201 is a mouse driver for INPUT A. This IC functions when connected to PS/2 and the serial port of
the computer, or connected to a Macintosh or NEC 98 series computer by USB. Identification of the
mouse of these computers is performed when power is supplied to IC1201. As power is supplied from the
computer except when connected by USB, connections can be identified even if AC is not supplied to the
unit. When connected by USB, the mouse cannot be identified if no power is supplied to the unit.
The mouse code input from CN1203"A1" is decided by IC1201, and output from CN1201 or I1202 to the
computer.
VPL-PX20/PX30
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