Philips Semiconductors
Preliminary specification
PAL/NTSC/SECAM decoder/sync processor
FEATURES
•
Multistandard PAL, NTSC and
SECAM
•
I
2
C-bus controlled
•
I
2
C-bus addresses can be selected
by hardware
•
Alignment free
•
Few external components
•
Designed for use with baseband
delay lines
•
Integrated video filters
•
Horizontal and vertical drive output
•
East-West correction drive output
•
Two CVBS inputs
•
S-VHS input
•
Vertical divider system
•
H
A
synchronization pulse
•
Two level sandcastle pulse
GENERAL DESCRIPTION
The TDA9160 is an I
2
C-bus
controlled, alignment-free
PAL/NTSC/SECAM
decoder/processor. The device
contains horizontal and vertical drive
outputs and an east-west correction
drive circuit. The TDA9160 has been
designed for use with baseband
chrominance delay lines and
DC-coupled vertical and east-west
output circuits.
The device has three inputs, two for
CVBS and one for S-VHS. The main
signal is available at the luminance
and colour difference outputs and,
also, at the TXT output
(unprocessed). The signal at the PIP
output can be selected independently
from the main signal.
The circuit provides a drive pulse for
the horizontal output stage, a
differential sawtooth current for the
vertical output stage and an east-west
TDA9160
drive current for the EW output stage.
These signals can be used to provide
geometry correction of the picture. A
two level sandcastle pulse and an H
A
pulse are made available for
synchronization purposes
.The I
2
C-bus address of the TDA9160
can be programmed by hardware.
Fig.1 Block diagram.
December 1991
2
Philips Semiconductors
Preliminary specification
PAL/NTSC/SECAM decoder/sync processor
FUNCTIONAL DESCRIPTION
The TDA9160 is an I
2
C-bus
controlled, alignment free
PAL/NTSC/SECAM colour
decoder/sync processor/deflection
controller which has been designed
for use with baseband chrominance
delay lines.
In the standard operating mode the
I
2
C-bus address is 8A . If the TXT
output is connected to the positive rail
the address will change to 8E
The standards which the TDA9160
can decode are dependent on the
choice of external crystals. If a
4.4 MHz and a 3.6 MHz crystal are
used then SECAM, PAL 4.4/3.6 and
NTSC 4.4/3.6 can be decoded. If two
3.6 MHz crystals are used then only
PAL 3.6 and NTSC 3.6 can be
decoded. Which 3.6 MHz standards
can be decoded is dependent on the
exact frequencies of the crystal. In an
application where not all standards
are required only one crystal is
sufficient (in this instance the crystal
must be connected to the reference
crystal input (pin 30)). If a 4.4 MHz
crystal is used it must always be
connected to pin 30. Both crystals are
used to provide a reference for the
filters and the horizontal PLL,
however, only the reference crystal is
used to provide a reference for the
SECAM demodulator.
To enable the calibrating circuits to be
adjusted exactly two bits from the
I
2
C-bus address are used to indicate
which crystals are connected to the
IC.
The standard identification circuit is a
digital circuit without external
components; the search loop is
illustrated in Fig.3.
The decoder (via the I
2
C-bus) can be
forced to decode either SECAM or
PAL/NTSC (but not PAL or NTSC).
Crystal selection can also be forced.
Information, concerning which
standard and which crystal have been
selected and whether the colour killer
is ON or OFF is provided by the read
out. Using the forced-mode does not
affect the search loop, it does,
however, prevent the decoder from
reaching or staying in an unwanted
state. The identification circuit skips
impossible standards (e.g. SECAM
when no 4.4 MHz crystal is fitted) and
illegal standards (e.g. forced mode).
To reduce the risk of wrong
identification PAL has priority over
SECAM (only line identification is
used for SECAM).
The TDA9160 has two CVBS inputs
and one S-VHS input which can be
selected via the I
2
C-bus. The input
selector can also be switched to
enable CVBS2 to be processed,
providing that there is no S-VHS
signal present at the input. If the input
selector is set to CVBS2 it will switch
to S-VHS if an S-VHS sync pulse is
detected at the luminance input. The
S-VHS detector output can be read
via the I
2
C-bus.
If the voltage at either the S-VHS
luminance or the chrominance input
(pins 22 and 23) exceeds +5.5 V the
IC will revert to test mode.
The TDA9160 also provides outputs
for picture-in-picture and teletext (PIP
pin 20 and TXT pin 25). The decoder
input signal can be switched directly
to the TXT output. The PIP output
signal can be selected independently
from the TXT output. If S-VHS is
selected at the TXT output only the
luminance signal will be present; if
S-VHS is selected at the PIP output
then the luminance and chrominance
signals will be added.
All filters, including the luminance
delay line, are an integral part of the
IC. The filters are gyrator-capacitor
type filters. The resonant frequency of
the filters is controlled by a circuit that
uses the active crystal to tune the
TDA9160
SECAM Cloche filter during the
vertical flyback time. The remaining
filters and the delay line are matched
to this filter. The filters can be
switched to either 4.43 MHz,
4.28 MHz or 3.58 MHz irrespective of
the frequency of the active crystal.
The switching is controlled by the
identification circuit.
The S-VHS luminance signal does
not pass through the notch filter to
preserve bandwidth. The luminance
delay line delivers the Y signal to the
output 40 ns after the
−(R-Y)
and
−(B-Y)
signals. This compensates for
the delay of the external chrominance
delay lines.
The PAL/NTSC demodulator
employs an oscillator that can operate
with either crystal (3.6 or 4.4 MHz). If
the I
2
C-bus indicates that only one
crystal is connected it will always
connect to the crystal at the reference
input (pin 30).
The Hue signal, which is adjustable
via the I
2
C-bus, is gated during the
burst for NTSC signals.
The SECAM demodulator is an
auto-calibrating PLL demodulator
which has two references. The
reference crystal, to force the PLL to
the desired free-running frequency
and the bandgap reference, to obtain
the correct absolute value of the
output signal. The VCO of the PLL is
calibrated during each vertical flyback
period, when the reference crystal is
active. When the second crystal is
active the VCO is not calibrated.
During this time the frequency of the
VCO is kept constant by applying a
constant voltage to its control input. If
the reference crystal is not 4.4 MHz
the decoder will not produce the
correct SECAM signals.
The main part of the sync circuit is a
432
×
f
H
(6.75 MHz) oscillator the
frequency of which is divided by 432
December 1991
5
Microcontroller MCU
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