VDP 31xxB
PRELIMINARY DATA SHEET
In each field two sets of measurements can be taken:
The vertical timing for the picture measurement is pro-
grammable, and may even be a single line. Also the sig-
nal bandwidth is switchable for the picture measure-
ment.
a) The picture tube measurement returns results for
– cutoff R
Two horizontal windows are available for the picture
measurement. The large window is active for the entire
activeline. Tubemeasurementisalwayscarriedoutwith
the small window. Measurement windows for picture
and tube measurement are shown in Figure 2–23.
– cutoff G
– cutoff B
– white drive R or G or B (sequentially)
tube measurement
picture meas. start
b) The picture measurement returns data on
– active picture maximum current
active video
field 1/ 2
– active picture minimum current
picture meas. end
The tube measurement is automatically started when
the cutoff blue result register is read. Cutoff control for
RGBrequiresonefieldonlywhileacompletewhite-drive
control requires three fields. If the measurement mode
is set to ‘offset check’, a measurement cycle is run with
the cutoff/whitedrive signals set to zero. This allows to
compensate the MADC offset as well as input the
leakagecurrents. Duringcutoffandwhitedrivemeasure-
ments, the average beam current limiter function (ref.
2.9.3.) is switched off and a programmable value is used
for the brightness setting. The start line of the tube mea-
small window for tube
measurement (cutoff, white drive)
large window for active picture
Fig. 2–23: Windows for tube and picture measure-
ments
2
surement can be programmed via I C-bus, the first line
used for the measurement, i.e. measurement of cutoff
red, is 2 lines after the programmed start line.
2.9.2. SCART Output Signal
The RGB output of the VDP 31xxB can also be used to
drive a SCART output. In the case of the SCART signal,
the parameter CLMPR (clamping reference) has to be
set to 1. Then, during blanking, the RGB outputs are au-
tomatically set to 50% of the maximum brightness. The
DC offset values can be adjusted with the cutoff parame-
ters CR, CG, and CB. The amplitudes can be adjusted
with the drive parameters WDR, WDG, and WDB.
The picture measurement must be enabled by the con-
trol microprocessor after reading the min./max. result
registers. If a ‘1’ is written into bit 2 in subaddress 25, the
measurement runs for one field. For the next measure-
ment a ‘1’ has to be written again. The measurement is
always started at the beginning of active video.
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Micronas
MICRONAS [ MICRONAS ]
