NEC PlasmaSync PX-42VM1G, Service Manual

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6-3
CIRCUIT DESCRIPTION
(7) RGB chrominance conversion and signal changeover block (IC7503)
IC7503 generates outputs to IC7506 through a changeover action between the video signal output from
the AD converter of IC6502 and another video signal output from the definition converter of IC8501. In
cases of video inputs, etc., the RGB signal is output after conversion into the 422-chrominance signal.
In the case of chrominance output, the R output of RGB falls on the CbCr output and the G output falls
on the Y output. Similarly as for the video signals, the clock output is obtained through a changeover
action between the sampling clock output from the AD converter of IC6502 and another clock signal
output (40MHz) on the output side of the definition converter block.
IC7502 is the programming ROM for IC7503.
(8) I-P converter and profile emphasis processor, and RGB chrominance converter block (IC7503)
In IC7506, and in the case of RGB input for video signals, DVD, and VIDEO, the horizontal interlace
signal of 15kHz is converted into the progressive signal of 31kHz (I-P conversion). For input signals in
other cases, processing for profile emphasis and noise reduction is carried out. In addition, for SXGA,
processing for enlargement and contraction is carried out. In cases of processing for I-P conversion and
that for enlargement and contraction, the SDRAM (IC7504, IC7505) is used.
The clock signal (Pin 18) is supplied from IC7503, while the sync signal (Pins 16 and 17) is fed from
IC9004.
IC7507 is the programming ROM for IC7506. In regard to the method of image display such as I-P
conversion, processing for profile emphasis, etc., control is effected by the microcomputer IC9501
through the I2C bus (SDAT3, SCL1).
The clock signal input for system operation is fed from IC7503 to IC7507 (20MHz). In IC6550, the
system reset terminals XRST and PLLRST operate when the potential is “H.”
(9) ON-screen signal generator block
IC9002 generates N-screen signals. The contents of display are controlled by the various signals of
SIDI, SIKI, and CSOSD fed from the microcomputer IC9501. The horizontal and vertical sync signals
are obtained from the signals of the IC9004 block and the clock signals (Pin 7 at 40MHz) are gained
from the signals of IC9005, both through the 3V
→
5V conversion at IC9001. The resultant signals are
fed to IC9002.
(10)
γ
processor, ON-screen synthesis processor block
In IC9004,
γ
processing is performed for the video signal. Synthesis of the ON-screen signal generated
at IC9002 is also conducted with the video signal. The obtained outputs are fed to the plasma display
module (the AD connector). In the case of RGB signals of video signals, DVD, and VIDEO, video
signals from the I-P converter and the profile emphasis processor (IC7506) are used (Pins 168 to 202).
In other cases of input signals, the video signals from the definition conversion processor (IC8501) are
used (Pins 97 to 130) through a changeover action. The clock signal (Pin 92 at 40MHz) to be used for
signaling is obtained from IC9005.
γ
processing is performed based on the data stored in IC9005. When the power supply is turned on,
data pickup into IC9004 is carried out.
IC9004 incorporates a pulse generator. Using the generated pulses of its own, video signal changeover
is performed (Pins 95 and 206). These pulses also function to select blanking. The right to left blanking
range is secured for normal display and so on. (Brightness can be set at the gray level.)
This IC9004 is controlled by the 3-wire bus (SID2, SIK2, CSTIR) extended from the microcomputer of
IC9501, signal reset signal (Pin 207, at 5V in normal operation), and video mute (Pin 94, at 5V in normal
operation). The system clock (Pin 209 at 40MHz) of IC9004 is obtained from IC7503.
(11) Plasma display module output block
The video signal output from IC9004 is processed for data latch at IC9006, IC9007, and IC9008. Since
then, the signal output is fed to the plasma display module (the AD connector).