ADVANCE INFORMATION
VDP 313xY
2.11.Video Back End
Cutoff and whitedrive current measurement are carried
out during the vertical blanking interval. They always
use the small bandwidth setting. The current range for
the cutoff measurement is set by connecting a sense
resistor to the MADC input. For the whitedrive mea-
surement, the range is set by using another sense
resistor and the range select switch 2 output pin
(RSW2). During the active picture, the minimum and
maximum beam current is measured. The measure-
ment range can be set by using the range select switch
1 pin (RSW1) as shown in Fig. 2–1 and Fig. 2–18. The
timing window of this measurement is programmable.
The intention is to automatically detect letterbox trans-
mission or to measure the actual beam current. All
control loops are closed via the external control micro-
processor.
The digital RGB signals are converted to analog RGBs
using three video digital to analog converters (DAC)
with 10-bit resolution. An analog brightness value is
provided by three additional DACs. The adjustment
range is 40 % of the full RGB range.
Controlling the whitedrive/analog brightness and also
the external contrast and brightness adjustments is
done via the Fast Processor, located in the front-end.
Control of the cutoff DACs is via I2C-bus registers.
Finally cutoff and blanking values are added to the
RGB signals. Cutoff (dark current) is provided by three
9-bit DACs. The adjustment range is 60 % of full scale
RGB range.
The analog RGB-outputs are current outputs with cur-
rent-sink characteristics. The maximum current drawn
by the output stage is obtained with peak white RGB.
An external half contrast signal can be used to reduce
the output current of the RGB outputs to 50 %.
beam current
SENSE
A
D
MADC
R2
R3
RSW1
RSW2
2.11.1.CRT Measurement and Control
The display processor is equipped with an 8-bit
PDM-ADC for all measuring purposes. The ADC is
connected to the sense input pin, the input range is 0
to 1.5 V. The bandwidth of the PDM filter can be
selected; it is 40/80 kHz for small/large bandwidth set-
ting. The input impedance is more than 1 MΩ.
R1
Fig. 2–1: MADC Range Switches
CR + IBRM + WDRV WDR
white
drive
R
CR + IBRM
cutoff
R
R
black
ultra black
CG + IBRM
cutoff
G
G
B
CB + IBRM
cutoff
B
active measure-
ment resistor
R1
R1||R2||R3
R1||R3
R1||R2||R3
RSW1=on, RSW2=on
PICTURE MEAS.
RSW2
=on
RSW1=on, RSW2=on
PICTURE MEAS.
PMSO
TUBE MEASUREMENT
TML
PMST
Lines
Fig. 2–18: MADC Measurement Timing
Micronas
21
MICRONAS [ MICRONAS ]
