HMP8112
TABLE 2. COMPATIBLE VIDEO INPUT STANDARDS
COLOR
SUBCARRIER
NUMBER OF
FIELDS PER
SECOND
NUMBER OF
VERTICAL
LINES
BLACK
SETUP TO
BLANK
LINE
FREQUENCY
NOMINAL
BANDWIDTH
STANDARD
f
SC
3.579545MHz
NTSC M
60Hz
50Hz
60Hz
50Hz
50Hz
525
625
525
625
625
15,734
(± 0.0003%)
4.2MHz
5.0MHz
4.2MHz
4.2MHz
4.2MHz
7.5 IRE
PAL B, D, G, H, I 4.43361875MHz
15,625
(± 0.02%)
0 IRE
PAL M
PAL N
3.579545MHz
4.43361875MHz
3.58205625MHz
15,750
(± 0.0003%)
7.5 IRE
7.5 IRE
7.5 IRE
15,625
(± 0.15%)
Special
Combination
PAL N
15,750
(± 0.15%)
VIDEO INPUT
VSYNC DETECT
THRESHOLD
LOW TIME
COUNTER
O
V
VSYNC
FIELD
6.5 LINES
‘EVEN’ FIELD
FIGURE 7. VSYNC TIMING AND THE EVEN TO ODD TRANSITION
VIDEO INPUT
VSYNC DETECT
THRESHOLD
LOW TIME
COUNTER
O
V
VSYNC
FIELD
6.5 LINES
‘ODD’ FIELD
FIGURE 8. VSYNC TIMING AND THE ODD TO EVEN TRANSITION
(4 x f )/CLK = Chroma PLL Value
SC
(4 x 3.579545MHz) / 27MHz = 0.5302895
In cases where VCRs are used in Pause, Fast Forward or
Fast Reverse, lines are typically dropped or added by the
VCR. In a worst case scenario a VCR line tolerance will vary
by ±8%. The standard detect logic checks the line count
against the given standard to determine an error. VCRs in
trick mode cannot cause a standard error. With an NTSC
standard VCR the number of lines in a field should not
exceed 285. Greater than 285 lines in a field is interpreted
as a PAL video source. An ideal NTSC source should have
262.5 lines per field and a PAL source should have 312.5
lines per field.
This value must be loaded to correctly separate and decode
the video signal. A default Chroma PLL Value is used after a
system RESET is applied. The default assumes a CLK of
27MHz and NTSC as the video standard. The default value
is 0.5302895. An ideal 4xf
NTSC and 1135 for PAL.
line should have 910 pixels for
SC
The Output Sample rate converter is locked to the horizontal
line frequency and is used to spatially align pixels in a field.
The LOCKED flag signals when the phase locked loop is
within a ±4 pixel range of the horizontal sync edge. When
line errors exceed that range the LOCKED flag is cleared.
The HMP8112 can detect a STANDARD Error that signals
when the video received does not match the standard that
was programmed into the Video Input Control Register. This
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