EP7209 Datasheet, PDF (78/128 Pages) Cirrus Logic – Ultra-Low-Power Audio Decoder System-on-Chip

EP7209
Bit
25:29
30
31
Description
AC prescale: The AC prescale field is a 5-bit number that sets the LCD AC bias frequency. This
frequency is the required AC bias frequency for a given manufacturer’s LCD plate. This fre-
quency is derived from the frequency of the line clock (CL[1]). The LCD M signal will toggle after
n+1 counts of the line clock (CL[1]) where n is the number programmed into the AC prescale
field. This number must be chosen to match the manufacturer’s recommendation. This is nor-
mally 13, but must not be exactly divisible by the number of lines in the display.
GSEN: Gray scale enable bit. Setting this bit enables gray scale output to the LCD. When this bit
is cleared each bit in the video map directly corresponds to a pixel in the display.
GSMD: Gray scale mode bit. Clearing this bit sets the controller to 2-bits per pixel (4 gray scales),
setting it sets it to 4 bits per pixel (16 gray scales). This bit has no effect if GSEN is cleared.
Table 45. LCDCON (cont.)
5.10.2 PALLSW Least Significant Word — LCD Palette Register
ADDRESS: 0x8000.0580
31:28
27:24
23:20
19:16
15:12
11:8
7:4
3:0
Gray scale Gray scale Gray scale Gray scale Gray scale Gray scale Gray scale Gray scale
value for pixel value for pixel value for pixel value for pixel value for pixel value for pixel value for pixel value for pixel
value 7
value 6
value 5
value 4
value 3
value 2
value 1
value 0
The least and most significant word LCD palette registers make up a 64-bit read/write register which
maps the logical pixel value to a physical gray scale level. The 64-bit register is made up of 16 x 4-bit
nibbles, each nibble defines the gray scale level associated with the appropriate pixel value. If the
LCD controller is operating in two bits per pixel, only the lower 4 nibbles are valid (D[15:0] in the least
significant word). Similarly, one bit per pixel means only the lower 2 nibbles are valid (D[7:0]) in the
least significant word.
5.10.3 PALMSW Most Significant Word — LCD Palette Register
ADDRESS: 0x8000.0540
31:28
27:24
23:20
19:16
15:12
11:8
7:4
3:0
Gray scale Gray scale Gray scale Gray scale Gray scale Gray scale Gray scale Gray scale
value for pixel value for pixel value for pixel value for pixel value for pixel value for pixel value for pixel value for pixel
value 15
value 14
value 13
value 12
value 11
value 10
value 9
value 8
The pixel to gray scale level assignments and the actual physical color and pixel duty ratio for the gray
scale values are shown in Table 46. Note that colors 8–15 are the inverse of colors 7–0 respectively.
This means that colors 7 and 8 are identical. Therefore, in reality only 15 gray scales available, not
16. The steps in the gray scale are non-linear, but have been chosen to give a close approximation
to perceived linear gray scales. The is due to the eye being more sensitive to changes in gray level
close to 50% gray (See PALLSW description).
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DS453PP2