VCT 38xxA
ADVANCE INFORMATION
In each field two sets of measurements can be taken:
tube measurement
picture meas. start
a) The picture tube measurement returns results for
– cutoff R
active video
field 1/ 2
– cutoff G
– cutoff B
picture meas. end
– white-drive R or G or B (sequentially)
b) The picture measurement returns data on
– active picture maximum current
– active picture minimum current
small window for tube
measurement (cutoff, white drive)
large window for active picture
The tube measurement is automatically started when
the cutoff blue result register is read. Cutoff control for
RGB requires one field only, whereas a complete
white-drive control requires three fields. If the mea-
surement mode is set to ‘offset check’, a measurement
cycle is run with the cutoff/white-drive signals set to
zero. This allows to compensate the MADC offset as
well as input the leakage currents. During cutoff and
white-drive measurements, the average beam current
limiter function (see Section 2.11.3. on page 27) is
switched off and a programmable value is used for the
brightness setting. The start line of the tube measure-
ment can be programmed via I2C bus, the first line
used for the measurement, i.e. measurement of cutoff
red, is 2 lines after the programmed start line.
picture meas. start
Fig. 2–21: Windows for tube and picture measure-
ments
2.11.2.SCART Output Signal
The RGB output of the VCT 38xxA can also be used to
drive a SCART output. In the case of the SCART sig-
nal, the parameter CLMPR (clamping reference) has to
be set to 1. Then, during blanking, the RGB outputs
are automatically set to 50 % of the maximum bright-
ness. The DC offset values can be adjusted with the
cutoff parameters 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 mea-
surement a ‘1’ has to be written again. The measure-
ment is always started at the beginning of active video.
The vertical timing for the picture measurement is pro-
grammable, and may even be a single line. Also the
signal bandwidth is switchable for the picture measure-
ment.
Two horizontal windows are available for the picture
measurement. The large window is active for the entire
active line. Tube measurement is always carried out
with the small window. Measurement windows for pic-
ture and tube measurement are shown in Fig. 2–21.
26
Micronas
MICRONAS [ MICRONAS ]
