SAA7121H/V2,557 Trident Microsystems, Inc., SAA7121H/V2,557 Datasheet - Page 28

• Manufacturer Part Number: SAA7121H/V2,557
• Manufacturer: Trident Microsystems, Inc.

Specifications of SAA7121H/V2,557

• Lead Free Status / RoHS Status: Supplier Unconfirmed

Philips Semiconductors
8.2
Time t
and insert it into the CVBS and Y 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.
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.
2002 Oct 11
handbook, full pagewidth
Digital video encoder
CVBS/Y
TTX
TTXRQ
FD
PD
Teletext timing
is the time needed to interpolate input data TTX
is the pipeline delay time introduced by the
TTX
= 9.78 s (PAL) or t
textbit #:
t PD
t TTX
1
2
t FD
3
TTX
4
= 10.5 s
5
6
Fig.10 Teletext timing.
7
8
9 10 11 12 13 14
28
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 (WST)
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 logic 0.
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.
TTXWin
t TTXWin
is the internally used insertion window for
15
SAA7120H; SAA7121H
16 17 18 19 20 21 22 23
Product specification
MBH788
24