Epson Research and Development
Page 35
Vancouver Design Center
Programming Notes and Examples
SED1352
Issue Date: 98/10/08
X16-BG-007-04
5.4.2 Description
A split screen is generally considered as the presentation of two different images on the screen. Image 1 is shown on the
top half and image 2 is shown on the bottom half of the screen. Due to the design the SED1352, the system is always in
split screen mode. If only one image is to be shown, either image 2 is hidden or image 2 appears as part of image 1; this
depends on whether a single or dual panel LCD is in use.
5.4.3 Single Panel LCD
The following is the procedure to show a split screen image on a 16 gray shade 320 x 240 single 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 320x240; only a portion of each image is shown.
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.
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.
Figure 11: Memory Map for Split Screen
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
Display Memory
Screen 1 Display Start Address
Image 1
C000:0000h
Screen 2 Display Start Address
Image 2
C000:9600h
(for this example)
16 gray shades => 4 bits per pixel
4 bits per pixel => 2 pixels per byte
number of bytes per scan line
pixels per scan line
pixels per byte
----------------------------------------------
320
2
---------
160 bytes per scan line
00A0h bytes per scan line
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