
4: LOOK-UP TABLE (LUT)
S1D13806 SERIES PROGRAMMING NOTES
EPSON
2-9
AND EXAMPLES (X28B-G-003-01)
4LOOK-UP TABLE (LUT)
This section discusses programming the S1D13806 Look-Up Table (LUT). Included is a summary
of the LUT registers, recommendations for color/gray shade LUT values, and additional program-
ming considerations. For a discussion of the LUT architecture, refer to the “S1D13806 Hardware
Functional Specification,” document number X28B-A-001-xx.
The S1D13806 is designed with a separate LUT for both the LCD and CRT/TV. Each LUT consists
of 256 indexed red/green/blue entries. Each LUT entry is four bits wide. The color depth determines
how many indices are used to output the image to the display. 4 bpp uses the first 16 indices, 8 bpp
uses all 256 indices, and 16 bpp color depths bypass the LUT entirely.
In color modes, the pixel values stored in the display buffer index directly to an RGB value stored in
the LUT. In monochrome modes, the pixel value indexes into the green component of the LUT and
the amount of green at that index controls the intensity. Monochrome mode look-ups are done based
on the Color/Mono Panel Select bit (REG[030h] bit 2). The CRT interface receives the RGB values
from the LUT even if simultaneous display is used with a monochrome panel. Therefore, it is impor-
tant to program the R, G, and B components of the CRT LUT either with a unique set of values, or
with R, G, and B values all equivalent.
4.1 Registers
The S1D13806 is designed with a separate LUT for both the LCD and CRT/TV. The LUT Mode
register selects which of the LUTs will be accessed by the CPU when reads/writes are made to
REG[1E2h] and REG[1E4h]. LUT mode selection allows the LUTs to be individually written or
have identical data written to both LUTs. Individual writes to these registers are useful for Epson
Independent Simultaneous Display (EISD) modes where independent images are displayed on the
LCD and the CRT/TV. For further information on Epson Independent Simultaneous Display, see the
“S1D13806 Hardware Functional Specification,” document number X28B-A-001-xx.
For normal operation, this register should be set to 00h which will read the LCD LUT and write both
the LCD and CRT/TV LUTs with identical data. For selection of other LUT modes, see REG[1E0h]
in the “S1D13806 Hardware Functional Specification,” document number X28B-A-001-xx.
REG[1E0h] Look-Up Table Mode Register
n/a
LUT Mode
Bit 1
LUT Mode
Bit 0