SAA7113 Philips Semiconductors, SAA7113 Datasheet - Page 13

• Manufacturer Part Number: SAA7113
• Description: 9-bit video input processor
• Manufacturer: Philips Semiconductors

Philips Semiconductors
8.3
The 9-bit chrominance signal is fed to the multiplication
inputs of a quadrature demodulator, where two subcarrier
signals from the local oscillator DTO1 are applied
(0 and 90 phase relationship to the demodulator axis).
The frequency is dependent on the present colour
standard. The output signals of the multipliers are
low-pass filtered (four programmable characteristics) to
achieve the desired bandwidth for the colour difference
signals (PAL, NTSC) or the 0 and 90 FM signals
(SECAM).
The colour difference signals are fed to the
Brightness/Contrast/Saturation block (BCS), which
includes the following five functions:
1999 Jul 01
AGC (automatic gain control for chrominance
PAL and NTSC)
Chrominance amplitude matching (different gain factors
for (R
C
Chrominance saturation control
handbook, full pagewidth
9-bit video input processor
WIPE = white peak level (254); SBOT = sync bottom level (1); CLL = clamp level [60 Y (128 C)];
HSY = horizontal sync pulse; HCL = horizontal clamp pulse.
R
and C
Chrominance processing
Y) and (B
B
for all standards)
NO BLANKING ACTIVE
CLAMP
Y) to achieve CCIR-601 levels
1
CLL
CLAMP
0
1
HCL
<- CLAMP
NO CLAMP
ANALOG INPUT
1
Fig.8 Clamp and gain flow.
0
VBLK
ADC
0
13
GAIN
The SECAM-processing contains the following blocks:
The burst processing block provides the feedback loop of
the chrominance PLL and contains:
0
Luminance contrast and brightness
Limiting YUV to the values 1 (minimum) and 254
(maximum) to fulfil CCIR-601 requirements.
Baseband ‘bell’ filters to reconstruct the amplitude and
phase equalized 0 and 90 FM signals
Phase demodulator and differentiator
(FM-demodulation)
De-emphasis filter to compensate the pre-emphasized
input signal, including frequency offset compensation
(DB or DR white carrier values are subtracted from the
signal, controlled by the SECAM switch signal).
Burst gate accumulator
Colour identification and killer
Comparison nominal/actual burst amplitude (PAL/NTSC
standards only)
SBOT
GAIN ->
1
1
GAIN
HSY
fast
0
GAIN
1
WIPE
slow
0
MGC647
GAIN
Product specification
SAA7113H