THS8200 Datasheet, PDF (33/97 Pages) Texas Instruments – ALL FORMAT OVERSAMPLED COMPONENT VIDEO/PC GRAPHICS D/A SYSTEM WITH THREE 11-BIT DACS,CGMS DATA INSERTION

dtg2_hs_in_dly
HS (Input)
RESET
Counter
>
=
RESET
Pixel
> Counter
=
dtg2_vs_in_dly
dtg2_hdly
RESET
Counter
>
<
HS_Out
VS (Input)
RESET
Counter
>
=
RESET
Line
> Counter
dtg2_hlength
=
dtg2_vdly
or
dtg2_vdly2
RESET
Counter
>
<
VS_Out
dtg2_vlength
or
dtg2_vlength2
Figure 4–15. THS8200 DTG VS/HS Output Generation
Note that both independent sets of delay registers allow accommodation of different input timing references in slave
mode. When the device is configured in master mode, the delay registers can compensate for different external
(frame memory) synchronization requirements.
4.7.2.3 Output Synchronization: Composite Sync
The composite sync is generated from a programmed sequence of (line type, breakpoint) combinations, either
user-programmed (in generic mode) or preset (in preset mode). The line type determines the waveform shape at the
output of the DAC(s) with programmable amplitudes and timings.
On each line, at the horizontal reference point of the DTG, the DTG decides where to start/stop the DTG-generated
data and where to pass input video data. For example, during an active video line, ancillary data can be embedded
in the digital stream outside the active video portion of the line, that we might want to convert to analog. Alternatively,
during a nonactive video line, where normally the predefined line type would be inserted, ancillary data might need
to be passed during the active video portion of the line.
The amplitudes of positive, negative sync excursions and of the negative serration, pre- and post-equalization and
broad pulses are independently programmable between G/Y and BPb, RPr channels. Therefore sync insertion can
be programmed on only the G/Y output or on all DAC outputs.
In order to limit the number of selection bits to select the line type, and because of the fact that we can define a set
of line types that is mutually exclusive for SDTV and HDTV video modes, there are two DTG video modes: SDTV and
HDTV. There is a third DTG mode (VESA) which does not use the line type/breakpoint state machine and only
generates Hsync/Vsync outputs.
4–18