SAA6721E Datasheet, PDF (54/72 Pages) NXP Semiconductors – SXGA RGB to TFT graphics engine

Philips Semiconductors
SXGA RGB to TFT graphics engine
Preliminary specification
SAA6721E
8.8 Overlay port
8.8.1 OVERLAY INSERTION
If ovl_syncs_active is HIGH, the vertical and horizontal
sync signals for the external OSD controller are generated.
The flag ovl_insert_active switches on the insertion of the
information at the overlay port provided by an external
OSD controller into the data stream at the position defined
by ovl_v_offset, ovl_hs_start, and ovl_hs_latency
(see Fig.18).
The incoming data from ports ovl0 and ovl1 is replaced by
the defined colour information and treated as a double
pixel, which will be inserted into the data stream if OVACT
is set. The pixel at port 0 is then the left pixel, and the pixel
at port 1 is the right pixel. The sampling of the ports ovl0
and ovl1 is done on the positive edge of OVCLK in the
event that sample_edge is asserted, otherwise on the
falling edge of OVCLK.
handbook, full pagewidth
ovl_hs_latency
ovl_hs_start
ovl_v_offset
ovl_h_length
ovl_v_length
ovl_vs_start
one line Vsync
OVERLAY
WINDOW
OUTPUT FRAME
Fig.18 Overlay window positioning.
MHB258
1999 May 11
54