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5.4.4 Dual Panel LCD
The following is the procedure to show a split screen image on a 4 gray shade 640x480 dual panel LCD. For this example
the SDU1352B0x is used; the Memory Interface is set to 16 bits, and 128k of display memory is available. In addition, the
two images shown on the split screen are each 640x240.
1.
Determine whether the Display Start Address Registers refer to bytes or words.
Since the Memory Interface is set to 16 bits, the Display Start Address Registers refer to words. Note that when ad-
dresses refer to words, the image must be aligned in memory such that the beginning is found on a word boundary
(the least significant bit of the memory address must be 0).
2.
Calculate the number of bytes per scan line.
4 gray shades => 2 bits per pixel
2 bits per pixel => 4 pixels per byte
number of bytes per scan line
3.
Determine the display memory location for image 1.
For simplicity, assign the beginning of display memory as the starting address of image 1 (see Figure 11). For the
SDU1352B0x, this address is C000:0000h.
4.
Program the Screen 1 Display Start Address Register to point to the beginning of image 1.
Since image 1 is at the beginning of display memory for a 128k system, program the Screen 1 Display Start Address
Register to 0000h.
AUX[06h] = 00h
AUX[07h] = 00h
5.
Calculate the total number of bytes required for image 1.
(
bytes per scan line
6.
Determine the display memory location for image 2.
Place image 2 immediately after image 1 (see Figure 11). Assign the starting address for image 2 as follows:
7.
Program the Screen 2 Display Start Address Register to point to the beginning of image 2.
Image 2 is placed right after image 1, as shown below:
Screen 2 Display Start Address
AUX[08h] = 00h
AUX[09h] = 4Bh
8.
Write both image 1 and image 2 to their respective locations in display memory.
SED1352
X16-BG-007-04
pixels per scan line
=
--------------------------------------------- -
pixels per byte
)
×
(
number of scan lines for image 1
(
image 2 address
=
base display memory address
=
C000:0000h
=
C000:9600h
=
Screen 1 Display Start Address
=
0000h
Epson Research and Development
640
=
-------- -
=
160 bytes per scan line
4
)
×
=
160 240
=
38400 bytes
)
(
+
size of image 1
+
0000:9600h
size of image 1 in bytes
+
--------------------------------------------------------
9600h
+
-------------- -
=
4B00h
2
Vancouver Design Center
=
00A0h bytes per scan line
=
9600h bytes
)
2 bytes per word
Programming Notes and Examples
Issue Date: 98/10/08
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