SDA9362 Datasheet, PDF (20/39 Pages) Siemens Semiconductor Group – DDC-PLUS-Deflection Controller

SDA 9362
PONRES:
Power On Reset
0: after bus master has read the status byte
1: after each detected reset
Note: PONRES is reset after this byte has been read.
2.5.5 Explanation of Some Control Items
Start Vertical Scan
If enabled (SSE = 1) this control item defines the start of calculation of the vertical
sawtooth, the east/west parabola and the vertical function required for the vertical
modulated output HD.
Vertical Scan (width0 and width1)
The total width of this control item is 10 Bit. Therefore two (width0 and width1) registers
are necessary. If enabled (STE = 1) it defines the duration of the vertical scan. When the
vertical period has more lines than the sum of Start Vertical Scan and Vertical Scan,
the calculation of the vertical sawtooth, the east/west parabola and the vertical parabola
required for HD stops so that the corresponding output signals remain unchanged till the
next vertical synchron pulse.
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 sawtooth 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.
Start Reduced Scan
If enabled (SRSE = 1) this item defines the start of the D/A-conversion of the calculated
vertical sawtooth. From begin of the vertical flyback to the line defined by Start Reduced
Scan the output signals VD+, VD- remain unchanged (flyback level). Other outputs are
not affected.
a) control bits VR1, VR0 # 00 (reduction of vertical size)
In this case the byte is useful for e.g. displaying 16/9 source format on 4/3 picture
tubes without visible RGB lines generated of the automatic cut-off control (partial
Semiconductor Group
20
1998-02-01