SAA7196 Datasheet, PDF (24/76 Pages) NXP Semiconductors – Digital video decoder, Scaler and Clock generator circuit DESCPro

Philips Semiconductors
Digital video decoder, Scaler and Clock
generator circuit (DESCPro)
Product specification
SAA7196
7.4.5.1 Vertical bypass region
Data are not scaled and independent of I²C bits FS1 and
FS0; the output format is always 8-bit gray scale
(monochrome). The SAA7196 outputs all active pixels of a
line, defined by the HREF input signal if the vertical bypass
region is active. This can be used, for example, to store
video text information in the field memory. The start line of
the bypass region is defined by the I²C bits VS;
the number of lines to be bypassed is defined by VC.
7.4.5.2 Vertical scaling region
Data is scaled with start at line YO and the output format
is selected when FS1 and FS0 are valid. This is the
‘normal operation’ area. The input/output screen
dimensions in horizontal and vertical direction are defined
by the parameters XO, XS and XD for horizontal and YO,
YS and YD for vertical.
The circuit processes XS samples of a line. Remaining
pixels are ignored if a line is longer than XS. If a line is
shorter than XS, processing is aborted when the falling
edge of HREF is detected. In this case the output line will
have less than XD samples.
7.4.5.3 Vertical regions (see Fig.12)
• The two regions can be programmed via I²C-bus,
whereby regions should not overlap (active region
overrides the bypass region)
• The start of a normal active picture depends on video
standard and has to be programmed to the correct value
• The offsets XO and YO have to be set according to the
internal processing delays to ensure the complete
number of destination pixels and lines (refer to Table 30)
• The scaling parameters can be used to perform a
panning function over the video frame/field.
handbook, full pagewidth
vertical sync
vertical bypass start
scaling region start
vertical
blanking
VS
YO
bypass region
scaling region
first valid line
vertical bypass count
equals VS
scaling region count
equals YS Y-size source
MHA392
Fig.12 Vertical regions.
1996 Nov 04
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