sed1355 ETC-unknow, sed1355 Datasheet - Page 180

• Manufacturer Part Number: sed1355
• Description: Sed1355 Embedded Ramdac Lcd/crt Controller
• Manufacturer: ETC-unknow

Page 24
5.1.1 Registers
5.1.2 Examples
SED1355
X23A-G-003-05
REG[16h] Memory Address Offset Register 0
REG[17h] Memory Address Offset Register 1
Memory
Address
Offset
Bit 7
n/a
Memory
Address
Offset
Bit 6
n/a
Registers [16h] and [17h] form an 11-bit value called the memory address offset. This offset is the
number of words from the beginning of one line of the display to the beginning of the next line of
the display.
Note that this value does not necessarily represent the number of words to be shown on the display.
The display width is set in the Horizontal Display Width register. If the offset is set to the same as
the display width then there is no virtual width.
To maintain a constant virtual width as color depth changes, the memory address offset must also
change. At 1 bpp each word contains 16 pixels, at 16 bpp each word contains one pixel. The formula
to determine the value for these registers is:
offset = pixels_per_line / pixels_per_word
Example 1: Determine the offset value required for 800 pixels at a color depth of 8 bpp.
At 8 bpp each byte contains one pixel, therefore each word contains two pixels.
Using the above formula.
Register [17h] would be set to 01h and register [16h] would be set to 90h.
Example 2: Program the Memory Address Offset Registers to support a 16 color (4 bpp)
To create a virtual display the offset registers must be programmed to the horizontal size of the larger
“virtual” image. After determining the amount of memory used by each line, do a calculation to see
if there is enough memory to support the desired number of lines.
1.
2.
Initialize the SED1355 registers for a 320x240 panel. (See Introduction on page 7).
Determine the offset register value.
Address
Memory
Offset
Bit 5
n/a
640x480 virtual display on a 320x240 LCD panel.
Figure 5-2: Memory Address Offset Registers
pixels_per_word = 16 / bpp = 16 / 8 = 2
offset = pixels_per_line / pixels_per_word = 800 / 2 = 400 = 190h words
Address
Memory
Offset
Bit 4
n/a
Memory
Address
Offset
Bit 3
n/a
Memory
Address
Memory
Address
Offset
Offset
Bit 10
Bit 2
Epson Research and Development
Programming Notes and Examples
Address
Address
Memory
Memory
Offset
Offset
Bit 1
Bit 9
Vancouver Design Center
Issue Date: 99/04/27
Address
Address
Memory
Memory
Offset
Offset
Bit 0
Bit 8