SAA7127 PHILIPS [NXP Semiconductors], SAA7127 Datasheet - Page 32

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

Philips Semiconductors
Teletext timing
Time t
and insert it into the CVBS and VBS output signal, such
that it appears at t
(NTSC) after the leading edge of the horizontal
synchronization pulse.
Time t
source that is gated by TTXRQ in order to deliver TTX
data. This delay is programmable by register TTXHD. For
every active HIGH state at output pin TTXRQ, a new
teletext bit must be provided by the source (new protocol)
or a window of TTXRQ going HIGH is provided and the
number of teletext bits, depending on the chosen TTX
standard, is requested at input pin TTX (old protocol).
Since the beginning of the pulses representing the TTXRQ
signal and the delay between the rising edge of TTXRQ
and valid teletext input data are fully programmable
(TTXHS and TTXHD), the TTX data is always inserted at
the correct position after the leading edge of outgoing
horizontal synchronization pulse.
1999 May 31
handbook, full pagewidth
Digital video encoder
CVBS/Y
TTX
TTXRQ (new)
TTXRQ (old)
d(pipe)(MP)
FD
is the time needed to interpolate input data TTX
is the pipeline delay time introduced by the
TTX
text bit #:
= 9.78 s (PAL) or t
t PD
t TTX
1
2
t FD
3
4
TTX
5
= 10.5 s
6
Fig.14 Teletext timing.
7
8
9 10 11 12 13 14
32
Time t
TTX data; it has a constant length that allows insertion of
360 teletext bits at a text data rate of 6.9375 Mbits/s
(PAL), 296 teletext bits at a text data rate of 5.7272 Mbits/s
(world standard TTX) or 288 teletext bits at a text data rate
of 5.7272 Mbits/s (NABTS). The insertion window is not
opened if the control bit TTXEN is zero.
Using appropriate programming, all suitable lines of the
odd field (TTXOVS and TTXOVE) plus all suitable lines of
the even field (TTXEVS and TTXEVE) can be used for
teletext insertion.
i(TTXW)
t i(TTXW)
is the internally used insertion window for
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SAA7126H; SAA7127H
16 17 18 19 20 21 22 23
Product specification
MHB504
24