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18.4.7.3 FOUR BITS PER PIXEL GRAYSCALE MODE. In 4-bits per pixel grayscale
mode, the LCD controller provides 16 possible shades to be loaded into each pixel of the
LCD panel. The four bits of data are provided by each display memory word that is accessed
by the DMA controller. This value will then index into the first 16 odd addresses of the color
RAM. You can provide any of the 16 possible shades by loading the color RAM addresses
shown below. See Figure 18-8 for more information.
BIT
0
1
2
FIELD
RESET
R/W
ADDR
NOTE: — = Undefined.
Bits 0–7—Reserved
These bits are reserved and must be set to 0.
GLCA/GLCB—Grayscale Level Code A and B
This field is a 4-bit code that represents any one of 16 possible grayscale levels for a given
pixel code. This grayscale level is then used to represent the appropriate shade for a given
pixel and is passed to the appropriate panel bit. GLCA and GLCB must be programmed to
the same value. The color RAM to be programmed is shown below.
MOTOROLA
3
4
5
6
7
RESERVED
—
R/W
(IMMR &0xFFFF0000) + (DPR) 0xE00—0xFFF
MPC823e REFERENCE MANUAL
8
9
10
11
12
13
GLCB
—
R/W
LCD Controller
14
15
GLCA
—
R/W
18-33
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