RM0082
RS_Color liquid crystal display controller (CLCD)
Doc ID 018672 Rev 1
745/844
For information on the numbers of colors supported, refer to
The palette RAM is a dual port RAM with independent controls and addresses for each port.
Port1 is used as a read/write port and is connected to the AMBA AHB slave interface. The
palette entries can be written and verified through this port. Port2 is used as a read-only port
and is connected to the unpacker and gray scaler.
shows the bit representation of each word in the palette.
For mono STN mode only the red palette field bits [4:1] are used. However, in STN color
mode the green and blue [4:1] are also used.
The red and blue pixel data can be swapped to support BGR data format using a control
register bit.
In 16 and 24 bpp TFT mode, the palette is bypassed and the output of the pixel serializer is
used as the TFT panel data.
33.5.6 Gray
scaler
A patented gray scale algorithm drives mono and color STN panels. This provides 15 gray
scales for mono displays. In the case of STN color displays, the three color components
(red, green, and blue) are gray scaled simultaneously which results in 3 375 (15x15x15)
colors being available. The gray scaler transforms each 4 bit gray value into a sequence of
activity-per-pixel over several frames, relying to some degree on the display characteristics,
to give the representation of gray scales and color.
33.5.7
Upper and lower panel formatters
Each formatter consists of three 3 bit (red, green, and blue) shift left registers. Red, green
and blue pixel data bit values from the gray scaler are concurrently shifted into the
respective registers. When enough data is available, a byte is constructed by multiplexing
the registered data to the correct bit position to satisfy the RGB data pattern of LCD panel.
The byte is transferred to the three-byte FIFO which has enough space to store eight color
pixels.
Table 672.
Palette data storage
Bit
Name
Description
[31]
I
Intensity/unused
[31:26]
B[4:0]
Blue palette data
[25:20]
G[4:0]
Green palette data
[19:16]
R[4:0]
Red palette data
[15]
I
Intensity/unused
[14:10]
B[4:0]
Blue palette data
[09:05]
G[4:0]
Green palette data
[04:00]
R[4:0]
Red palette data