SDA 9380 - B21
Preliminary Data Sheet
System description
5.5.5 Explanation of some control items
Vertical aspect,
Vertical scroll:
Two special control items are implemented for the user to adjust the
vertical height (control item: Vertical aspect) and the vertical position
(Vertical scroll). These items may be stored for every display mode to
get an individual height and position if desired. Changing these para-
meters automatically influences the outputs VD+, VD-, E/W, HD in such
a way that absolutely no raster distortion happens. There is no need
for the user to re-adjust any geometry parameter.
The difference of the function of Vertical size and Vertical aspect is
the following: Varying Vertical size causes a linear stretching of the
saw-tooth to eliminate the tolerance of linear components (e.g. feed-
back resistor). But adjusting Vertical aspect takes into consideration
that more or less picture height needs very more or less S-correction
(no linear relation). Therefore Vertical aspect should be used for chang-
ing the aspect ratio (e.g. 16:9 source on 4:3 CRT) or if an individual
picture height is desired for the various PC graphic standards. Vertical
aspect = -128(minimum value) results in a vertical reduction to 37.5%.
Vertical size,
Vertical shift:
The purpose of these control parameters is the alignment in the factory
and service to adapt the output signals VD+, VD- to the picture tube and
to eliminate tolerances of the hardware and deflection yoke. Only one
set of these parameters is required for all display modes.
Vertical linearity,
Changing the vertical linearity and S-correction has no influence on the
Vertical S-correction: E/W-geometry. That means, straight vertical lines remain straight. The
output signals E/W and HD are automatically changed so no re-adjust-
ment of the related control items is needed. This feature saves time for
adjustment of the so called ’smart’ mode (4:3 source on 16:9 CRT)
Guard band:
This control item is useful for optimizing self adaptation. Video signals
with different number of lines in consecutive fields (e.g. VCR search
mode) must not start the procedure of self adaptation. But switching
between different TV standards has to change the slope of the vertical
saw-tooth getting always the same amplitude (self adaptation). To avoid
problems with flicker free TV systems which have alternating number of
lines per field an average value of four consecutive fields is calculated. If
the deviation of these average values (e.g. PAL : 312.5 lines or 625 half
lines) is less or equals Guard band, no adaptation takes place. When it
exceeds Guard band, the vertical slope will be changed.
Vertical EHT comp.: This item controls the influence of the beam current dependent input
signal IBEAM on the outputs VD+ and VD- according to the following
equation:
Vertical_EHT_compensation + 128
-------------------------------------------------------------------------------------
∆V
= ∆V
0.59 (if RIBM=0)
0.59 (if RIBM=1)
VDPP
VDPP
IBEAM
IBEAM
1536
Vertical_EHT_compensation + 128
-------------------------------------------------------------------------------------
512
∆V
= ∆V
∆V
: variation of VD+ and VD-peak-to-peak voltage
VDPP
Micronas
5-29
2001-01-29
MICRONAS [ MICRONAS ]
