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Alternate portrait mode
Alternate portrait mode does not require extra display memory as in default portrait mode. To display the
same horizontal 240-pixel image as in the above example, the display memory requires byte counts for only
240 pixels per line. Although alternate portrait mode provides higher display performance than default
portrait mode, it requires a clock twice as fast at the same frame rate, resulting in larger current consumption.
A
Physical memory
start address
320 lines
C
Display memory
Figure 2.21 shows the relationship between the display memory and the LCD panel in cases in which a 320
240-pixel LCD panel is rotated 90 degrees to display a 240 320-pixel image.
The control procedure described below assumes that the LCD panel is used in 8-bpp mode.
1. Make settings necessary to use an LCD panel consisting of 320 pixels horizontally and 240 lines
vertically. If necessary, set it for display in normal (landscape) mode.
2. To switch from landscape mode to portrait mode, temporarily clear the display memory in advance. If
switched over without clearing the display memory, the display may be distorted for a certain period.
3. If the LCD panel was split into two screens in landscape mode, reset the S1VSIZE[9:0] (D[9:0])/screen 1
vertical size register (0x39FFF2) by setting a new value above the vertical resolution of the LCD panel in
it. In portrait mode, the LCD panel cannot be split for display on screen 2.
4. Write a portrait-mode display image into memory, such as A
5. In the line byte-count register (0x39FFFC) for portrait-mode use, set the number of bytes equivalent to
one line of portrait display (240 pixels). For 8-bpp mode, with one pixel per byte, it is 240 bytes (0xF0).
Write 0xF0 to the line byte-count register (0x39FFFC) for one-byte line count. Even in the case of
alternate portrait mode, the horizontal size of an image that can be displayed in 8-bpp portrait mode is
maximum of 256 pixels. For 4-bpp mode, with 2 pixels per byte, the byte count is 240/2 = 120 (0x78).
This value indicates the distance in memory between one piece of pixel data and the next piece of pixel
data when displayed in portrait mode.
6. Write the display memory address at which pixel B exists to the screen 1 start address register
(0x39FFEC, 0x39FFED, D0/0x39FFF0). Although halfword addresses are set in this register in landscape
mode, addresses must be set in byte units in portrait mode. In the example discussed here, because pixel
A is at 0x0, the offset from A to B is 240 - 1 = 239 (0xEF) bytes. For 4-bpp mode, this is 240/2 - 1 = 119
(0x77) bytes.
S1C33L03 FUNCTION PART
240 pixels
B
Screen 1
start address
Image
D
Figure 2.21 Image Rotation in Alternate Portrait Mode
EPSON
VII LCD CONTROLLER BLOCK: LCD CONTROLLER
320 pixels
Line 1
Line 240
LCD panel
B ... C
D.
A-1
240 lines
B-VII
LCDC
B-VII-2-27
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