Philips SAA7102 Datasheet page 68

Philips Semiconductors
Digital video encoder
11.1 Teletext timing
Time t is the time needed to interpolate input data TTX
FD
and insert it into the CVBS and VBS output signal, such
= 9.78 µs (PAL) or t
that it appears at t
TTX
(NTSC) after the leading edge of the horizontal
synchronization pulse.
Time t is the pipeline delay time introduced by the
PD
source that is gated by TTXRQ_XCLKO2 in order to
deliver TTX data. This delay is programmable by register
TTXHD. For every active HIGH state at output pin
TTXRQ_XCLKO2, a new teletext bit must be provided by
the source.
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 the outgoing
horizontal synchronization pulse.
handbook, full pagewidth
CVBS/Y
text bit #:
TTX_SRES
TTXRQ_XCLKO2
2004 Mar 01
= 10.5 µs
TTX
t TTX
1 2 3 4 5 6
t PD t FD
Time t
i(TTXW)
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.
It is essential to note that the two pins used for teletext
insertion must be configured for this purpose by the
2
correct I C-bus register settings.
t i(TTXW)
7 8 9 10 11 12 13 14
Fig.14 Teletext timing.
68
SAA7102; SAA7103
is the internally used insertion window for
15 16 17 18 19 20 21 22 23
Product specification
24
MHB891