User`s manual

Reference Manual 135
Context
OSD Font Bitmaps
All OSD font bitmaps are stored in the off-chip DRAM. The
address is from 0xA0100 to 0xAF8FF (if 8M SDRAM and
IP_ONLY), or from 0x140100 to 0x14F8FF (if 8M SDRAM and
IPB). Each font occupies 32 consecutive DWORD, supporting up
to 1984 font bitmaps. After downloading to DRAM, the bitmaps are
never changed.
OSD Fonts Display
There is a 192-WORD font index buffer in the on-chip SRAM. It is
separated into two 96-WORD buffers: index_buffer1 (0x3A00-
0x3A5F) and index_buffer2 (0x3A60-0x3ABF). At any time, one of
them contains an OSD frame which is currently in use; the other is
open for editing the next OSD frame. Here, an OSD frame means
a layout of OSD fonts. A series of consecutive video frames may
share one single OSD frame.