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Número de pieza SAA4977H
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No Preview Available ! SAA4977H Hoja de datos, Descripción, Manual

INTEGRATED CIRCUITS
DATA SHEET
SAA4978H
Picture Improved Combined
Network (PICNIC)
Product specification
Supersedes data of 1998 Oct 07
File under Integrated Circuits, IC02
1999 May 03

1 page




SAA4977H pdf
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YC8
to
WEC IEC YC0
UVC8
to
UVC0
UVD0 YD0
to to
UVD8 YD8
RED
SPECTRAL
MEASUREMENT
NOISE
ESTIMATION
A
SUBTITLE
DETECTION
BLACK BAR
DETECTION
NOISE
REDUCTION
HISTOGRAM
MODIFICATION
B
113 112 114 to 122 124 to 132
3-STATE
DITHER
DOWNSAMPLER
DITHER
FORMATTER
5
DITHER
8 DPCM 4
CODER
MUX
bus C
SPECIAL FUNCTION
REGISTERS
VARIOUS
REGISTERS
AUXILIARY
RAM
PROGRAM
ROM
91 101 to 109 110
to 99
UNDITHER
SPECTRAL
MEASUREMENT
MUX
DYNAMIC 10
PEAKING
NON-LINEAR 10
PHASE
FILTER
5
REFORMATTER
UPSAMPLER
4
DPCM DECODER
MUX
10
DCTI
10
BORDER
BLANK
DAC
TRIPLE
10-BIT
bus D
SAA4978H
PIXREP BLANKING
BORDER
12 YOUT
TRIPLE
ANALOG
POST-FILTER
14
UOUT
15 VOUT
C SKEWEN CL16
CL16
CL16
CL16
HREF
SKEW
CL32
D
DATA8
INT1 INT0 P1.4
P1.1
80C51 MICROCONTROLLER CORE
bone
P1.5
EA PSEN P3.5 P3.4 P1.2 P1.3 P1.7 P1.6 RST
WATCHDOG
FREQUENCY
GUARD
PLL
E
F
G
12
SNDA SNCL
140 149
to to
147 156 136 137 138 160 159 8 9 5 4 6
P2.7 P0.7 EA
ALE
T0 RSTR SCL
to to
P2.0 P0.0
PSEN T1
RSTW SDA
RST
OR
42, 63, 86,
111, 133, 3 52, 123, 148
7
88
CRYSTAL
OSCILLATOR
89 28
34
35
WDRST
VSSO1
to
VSSO6
VDDO1
to
VDDO3
CLK16 CLK32 HA
OSCI
OSCO
MHB173
Standard bus width in data path is 9 bits; exceptions are marked.
Fig.2 Block diagram (continued from Fig.1).

5 Page





SAA4977H arduino
Philips Semiconductors
Picture Improved Combined Network
(PICNIC)
Product specification
SAA4978H
A voltage controlled current source construction, which
references to voltage reference points in the ladders of the
analog-to-digital converters, provides a current on the
input of the YUV signals in order to bring the signals to the
correct DC value. This current is proportional to the DC
error, but is limited to ±150 µA. It is essential that the clamp
current becomes zero with a zero error and that the
asymmetry between positive and negative clamp currents
is limited to within 10%. When the clamping action is off,
the residual clamp current should be very low, so that the
clamp level will not drift away within a video line.
The clamp level in the Y channel has a minimum value of
600 mV to ensure undisturbed clamping for maximum
Y input signals with top sync levels up to 600 mV. In order
to improve common mode rejection it is recommended to
connect the same source impedance as used in the YIN
input at the DIFFIN input to ground.
7.1.3 ANALOG ANTI-ALIASING PREFILTER
A 3rd-order linear phase filter is applied to each of the
Y, U and V channels. It provides a notch on fclk (16 MHz
at Y, U and V) to strongly prevent aliasing to low
frequencies, which would be the most disturbing.
The bandwidth of the filters is designed for 3 dB at
5.6 MHz. The filters can be bypassed if external filtering
with other characteristics is desired. In the bypass mode
the gain accuracy of the front-end part is 4% instead of 8%
for the filter-on mode.
7.1.4 9-BIT ANALOG-TO-DIGITAL CONVERSION
Three identical multi-step type analog-to-digital converters
are used to convert the Y, U and V inputs with a 16 MHz
data rate. The ADCs have a 2-bit overflow detection, and
an underflow detection for U and V, to be used for AGC
control. The 2 bits are coded for one in-range level and
three overflow levels; 1 dB, 1 to 2 dB and 2 to 3 dB.
7.2 Digital processing blocks
7.2.1 OVERFLOW DETECTION
A histogram of the three overflow levels is made every field
and can be read in a 2-byte accuracy. An input selector
defines which ADC is monitored.
In the event of U or V selection the underflow information
is also added to the first histogram level, in this way the
data can be handled as out-of-range information.
The histogram content provides information for the AGC to
make an accurate estimate of the decrease in gain, in the
event of overflow for luminance or out-of-range detection
for U and V.
7.2.2 Y DELAY
The Y samples can be shifted onto 4 positions with
respect to the UV samples. This shift is meant to account
for a possible difference in delay prior to the SAA4978H,
e.g. from a prefilter in front of an analog-to-digital
converter. The zero delay setting is suitable for the
nominal case of aligned input data according to the
interface format standard. One setting provides one
sampleless delay in Y, the other two settings provide more
delay in the Y path.
7.2.3 TRANSIENT NOISE SUPPRESSION
A circuit is added in the luminance channel to suppress the
typical multi-step trip level noise. This majority follower
filter compares the neighbouring pixels to a +1 or 1 LSB
difference. If the majority of these differences is +1 then 1
is added to the actual pixel. If the majority of these
differences is 1 then 1 is subtracted from the actual pixel.
The number of pixels included in the filter is selectable;
1 (bypass), 3, 5, 7 or 9.
7.2.4 NON-LINEAR PHASE FILTER AFTER ADC
The non-linear phase filter adjusts for possible group delay
differences in the luminance channel. The filter coefficients
are [L × (1 u); 1 + L; L × u]; where L determines the
strength of the filter and u determines the asymmetry.
The effect of the asymmetry is that for higher frequencies
the delay is decreased for u 0.5. Settings are provided
for L = 0, 116, 216 and 316 and u = 0, 14 and 12.
7.2.5 4 MHZ NOTCH
The 4 MHz notch provides a zero on 14 of the sample
frequency. With fs = 16 MHz the notch is thus at 4 MHz.
The 3 dB notch width is 2 MHz. The filter coefficients are
18 × [1; 0; 5; 0; 5; 0; 1]. This filter gives a relative gain of
0.75 dB at 1.7 and 6.3 MHz.
The notch can be bypassed without changing the group
delay.
7.2.6 DIGITAL CLAMP CORRECTION FOR UV
During 32 samples within the active clamping the clamp
error is measured and accumulated to determine a
low-pass filtered value of the clamp error. A vertical
recursive filter is then used to further reduce this error
value. This value can be read by the microcontroller or be
used directly to correct the clamp error. It is also possible
for the microcontroller to give a fixed correction value.
1999 May 03
11

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