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6-7. BUF Board (only 24 inch)
The BUF board sends the dynamic correction signals to the GAIN control terminals of the R. G. B.
channels in the BK (VIDEO OUT) board corresponding the respective positions of the CRT screen
positions in order to improve the luminance errors due to non-uniformity of the CRTs. This provides the
high quality and uniform white screen over the entire areas from the center up to the corners of the CRT
screen.
1. Interface
The interface with the CPU is established using the serial communication of 3-wire bus. Writing and
reading to and from the internal register are performed using the signals of A3 to A0, D7 to D0, _WR and
_RD signals.
Various data such as board ID and others are stored in the EEPROM IC903.
2. SRAM memory specifications
The BUF board has the data structure consisting of 8-bit data for each of the R. G. B. channels (horizontal
32 x vertical 16) for every format of each scan. The formats and scans can be switched by specifying the
SRAM address MA16 to MA11. The SRAM is backed up by the lithium battery.
3. PLL
The AFC.P pulse coming from the deflection circuit and the H.OUT signal coming from the H address
generator circuit inside the PLD are inputted to the PLL IC104 where PLL is established. The fundamen-
tal CLK for the data processing circuit is obtained from the PLL output.
4. Data processing circuit
The desired data can be read from the SRAM by accessing the SRAM using the addresses of H8 to H0
and V3 to V0 that are generated by the H address generator circuit and the V address generator circuit that
correspond to the raster scanning. The read-out data form the SRAM is D/A converted, passed through a
low-pass filter and clamped to generate the correction waveforms. The correction waveforms are sent to
the respective GAIN control terminal of Red, Green and Blue of the BK (VIDEO OUT) board. The
linear interpolation between the data in the direction is created. At the same the horizontal interpolation
is created by implementing the linear interpolation between the horizontal data.
Data read-out requires the real time processing. However, because data must be re-written in the event of
adjustment, the interrupt processing is used to stop read-out from the SRAM and data is written into the
SRAM.
5. Cursor generator circuit
For the purpose of user interface, correlation between the adjustment position and the correction wave-
form is established when the cursor is placed on the CHAR_BLK line.
The cursor position can be changed by specifying the desired SRAM address of MA10 to MA0. The
number of data is 32 x 16 per every screen. Because amount of data is too many and the cursor area for a
data is too small, several data in the vertical and horizontal directions are grouped together as one data
block. Size of the cursor is changed in accordance with the size of the group data. This grouping can
shorten the adjustment time. In addition to grouping, the linear interpolation is established between the
several data in the horizontal and vertical directions within one block by means of software. (It means
that the data are interpolated by means of both software and hardware.)
6-18BVM-D20F1A/D20F1E/D20F1U/D24E1WA/D24E1WE/D24E1WU |
ACEC
SONY
