SED1374 Datasheet, PDF (110/420 Pages) Epson Company – SED1374 Embedded Memory Color LCD Controller

Page 14
Epson Research and Development
Vancouver Design Center
4 Look-Up Table (LUT)
This section is supplemental to the description of the Look-Up Table (LUT) architecture
found in the SED1374 Hardware Functional Specification. Covered here is a review of the
LUT registers, recommendations for the color and monochrome LUT values, and
additional programming considerations for the LUT.
The SED1374 Look-Up Table consists of sixteen 4-bit wide entries for each of red, green
and blue. The Look-Up Table is controlled by three registers. REG[15h] forms the index
into the table. REG[16h] determines which bank is active during display. REG[17h] is the
register where the Look-Up Table data is read and written.
The currently configured color depth affects how many indices will be used for image
display. In color modes, pixel values are used as indices to an RGB value stored in the
Look-Up Table. In monochrome modes only the green component of the LUT is used.
4.1 Look-Up Table Registers
REG[15h] Look-Up Table Address Register
n/a
n/a
RGB Index
bit 1
RGB Index
bit 0
Read/Write
LUT Address LUT Address LUT Address LUT Address
Bit 3
Bit 2
Bit 1
Bit 0
RGB Index
The RGB Index bits determine how the SED1374 will handle automatic LUT Address
updates.
When the RGB Index is set to auto-increment (00) then three consecutive accesses of
REG[17h] will read/write the red, green, and then the blue elements at the Look-Up Table
index specified by the LUT Address. After three accesses of REG[17h] the LUT Address
is incremented. The next access of REG[17h] will be the red element from the new Look-
Up Table address.
By altering the RGB Index the sequence can be changed such that three accesses of
REG[17h] will affect just the reds or just the greens or just the blues at three different LUT
addresses.
When configured for monochrome panels the mechanism in which writes are handled is
slightly different. One to three reads are still required to update the LUT Address depending
on the setting of the RGB Index bits. If the RGB Index bits are set to auto-increment then
three writes to REG[17h] are required to bump the LUT Address. Only the last write will
affect the display appearance; it is copied across all three RGB elements. If the RGB Index
is set to access just red, just green or just blue then a single write to REG[17h] is copied to
the red, green and blue elements of the lookup address and the LUT Address is incre-
mented.
SED1374
X26A-G-002-02
Programming Notes and Examples
Issue Date: 99/04/27