TMC22x5yA
PRODUCT SPECIFICATION
Table 10. PAL-M Bruch Blanking Sequence
Internal
line #
Burst
present
Internal
frame #
0
-10
-20
-30
-40
-50
-60
-70
Internal field #
0 or 4
7
258
7
No
Yes
No
0 or 2
0 or 2
0 or 2
0 or 2
1 or 3
1 or 3
1 or 3
1 or 3
Demodulator Filter 1
0 or 4
1 or 5
Demodulator Filter 2
259
7
No
1 or 5
Yes
No
2 or 6
258
7
2 or 6
Yes
Yes
3 or 7
259
3 or 7
Normalized Frequency
Figure 22. Gaussian Low Pass Filters
The frame bit is low for frames 0 and 2 and high for frames 1
and 3.
PAL Color Frame Bit
0
-2
The PAL color frame bit is the msb of the field count, FID .
2
In NTSC this is always low, as NTSC has only a 4 field se-
quence. For both PAL-I and PAL-M inputs, the PAL color
frame bit is determined in the same way the frame bit is de-
termined in NTSC, by using the phase of the subcarrier on a
given pixel and on a given line.
Demodulator Filter 1
-4
-6
Demodulator Filter 2
-8
Hue Control
One of two programmable 16 bit system phase offsets can be
added to the subcarrier oscillator between SAV and EAV.
The selection is made by the BUFFER pin. This feature
allows the user to change the picture hue on known frames
without affecting the burst locked loop.
-10
Normalized Frequency
Figure 23. Gaussian LPF Passband Detail
Bypassing the Chrominance Demodulator
The demodulation of the chrominance signal needs to be
System Monitoring of the Burst Loop Error
The burst loop error signal is stored once per line in an 8 bit
register that can be accessed over the microprocessor port.
This allows the user to check for non-mathematical PAL in-
puts and to the change the decoder architecture from frame-
based to line-based or simple decoder depending on this in-
formation.
bypassed when the decoder is processing C C component
B R
data or when a YC output is required. The bypass operation
is controlled by the DMODBY register bit.
Bypassing the Demodulation Low Pass Filter
The demodulation low pass filter needs to be bypassed when
processing C C component data or when a YC output is
required. The C C data can also be passed through the
B R
B R
Demodulation Low Pass Filter
There are two different demodulation low pass filters that
can be selected under software. For PAL inputs with normal-
ized subcarrier frequencies greater than 0.3 of the sampling
frequency, it is recommended you use “demodulator filter 2”
to stop aliasing of the second harmonic of the demodulation
chrominance signal and the baseband color difference sig-
nals. Gaussian filters are used for both demodulation filters
as they have no negative coefficients and therefore have no
undershoots or overshoots which could cause in-band
ringing.
Gaussian filter if the bandwidth needs to be reduced. The
bypass operation is controlled by the GAUBY register bit.
Chrominance Coring
Chrominance coring, when active, sets the lsbs of the
chroma channel (below a programmable threshold) to zero.
VMCR Operation
5
When VMCR is HIGH, the decoder will grab one line of
5
video in LSTORE1. This effectively removes the comb filter
from the decoding process, and the comb filter output is
forced to simple mode.
54
REV. 1.0.0 2/4/03
CADEKA [ CADEKA MICROCIRCUITS LLC. ]
