SAA7127 PHILIPS [NXP Semiconductors], SAA7127 Datasheet - Page 8

• Manufacturer Part Number: SAA7127
• Description: Digital video encoder
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
Synchronization
The synchronization of the SAA7126H; SAA7127H is able
to operate in two modes; slave mode and master mode.
In master mode (see Fig.10), the circuit generates all
necessary timings in the video signal itself, and it can
provide timing signals at the RCV1 and RCV2 ports.
In slave mode, it accepts timing information either from the
RCV pins or from the embedded timing data of the
CCIR 656 data stream.
For the SAA7126H; SAA7127H, the only difference
between master and slave mode is that it ignores the
timing information at its inputs in master mode. Thus, if in
slave mode, any timing information is missing, the IC will
continue running free without a visible effect. But there
must not be any additional pulses (with wrong phase)
because the circuit will not ignore them.
In slave mode (see Fig.9), an interface circuit decides,
which signal is expected at the RCV1 port and which
information is taken from its active slope. The polarity can
be chosen, if PRCV1 is logic 0 the rising slope will be
active.
The signal can be:
On the RCV2 port, the IC can provide a horizontal pulse
with programmable start and stop phase; this pulse can be
inhibited in the vertical blanking period to build up, for
example, a composite blanking signal.
The horizontal phase can be set via a separate input
RCV2. In the event of VS pulses at RCV1, this is
mandatory. It is also possible to set the signal path to blank
via this input.
From the CCIR 656 data stream, the SAA7126H;
SAA7127H decodes only the start of the first line in the odd
field. All other information is ignored and may miss. If this
kind of slave mode is active, the RCV pins may be
switched to output mode.
In slave mode, the horizontal trigger phase can be
programmed to any point in the line, the vertical phase
1999 May 31
A Vertical Sync (VS) pulse; the active slope sets the
vertical phase
An odd/even signal; the active slope sets the vertical
phase, the internal field flag to odd and optionally sets
the horizontal phase
A Field Sequence (FSEQ) signal; it marks the first field
of the 4 (NTSC) or 8 (PAL) field sequence. In addition to
the odd/even signal, it also sets the PAL phase and
optionally defines the subcarrier phase.
Digital video encoder
8
from line 0 to line 15 counted from the first serration pulse
in half line steps.
Whenever a synchronization information cannot be
derived directly from the inputs, the SAA7126H;
SAA7127H will calculate it from the internal horizontal,
vertical and PAL phase. This gives good flexibility with
respect to external synchronization but the circuit does not
suppress illegal settings. In such an event, e.g the
odd/even information may vanish as it does in the
non-interlaced modes.
In master mode, the line lengths are fixed to 1728 clocks
at 50 Hz and 1716 clocks at 60 Hz. To allow
non-interlaced frames, the field lengths can be varied by
SAA7127H does not provide odd/even information and the
output signal does not contain the PAL ‘Bruch sequence’.
At the RCV1 pin the IC can provide:
At the RCV2 pin, there is a horizontal pulse of
programmable phase and duration available. This pulse
can be suppressed in the programmable inactive part of a
field giving a composite blank signal.
The directions and polarities of the RCV ports can be
chosen independently. Timing references can be found in
Tables 29 and 37.
Clock
The input at LLC1 can either be an external clock source
or the buffered on-chip clock XCLK. The internal crystal
oscillator can be run with either a 3rd-harmonic or a
fundamental crystal.
I
The I
supporting 7-bit slave addresses and 400 kbits/s
guaranteed transfer rate. It uses 8-bit subaddressing with
an auto-increment function. All registers are write and
readable, except one read only status byte.
The I
(SA) tied LOW and as 8CH with pin 21 (SA) tied HIGH.
2
0.5 lines. In the event of non-interlace, the SAA7126H;
C-bus interface
A Vertical Sync (VS) signal with 2.5 (50 Hz) or 3 (60 Hz)
lines duration
An odd/even signal which is LOW in odd fields
A Field Sequence (FSEQ) signal which is HIGH in the
first field of the 4 or 8 field sequence.
2
2
C-bus interface is a standard slave transceiver,
C-bus slave address is defined as 88H with pin 21
SAA7126H; SAA7127H
Product specification