Philips S1D13505 用户手册

Page 24

Epson Research and Development

Vancouver Design Center

S1D13505

Programming Notes and Examples

X23A-G-003-07

Issue Date: 01/02/05

8 bpp color

When the S1D13505 is configured for 8 bpp color mode all 256 entries in the LUT are used.
Each byte in display buffer corresponds to one pixel and is used as an index value into the
LUT.

The S1D13505 LUT has four bits (16 intensities) of intensity control per primary color
while a standard VGA RAMDAC has six bits (64 intensities). This four to one difference
has to be considered when attempting to match colors between a VGA RAMDAC and the
S1D13505 LUT. (i.e. VGA levels 0 - 3 map to LUT level 0, VGA levels 4 - 7 map to LUT
level 1...). Additionally, the significant bits of the color tables are located at different offsets
within their respective bytes. After calculating the equivalent intensity value the result must
be shifted into the correct bit positions.

The following table shows LUT values that will approximate the VGA default color palette.

Table 4-5: Suggested LUT Values to Simulate VGA Default 256 Color Palette

Index