Epson Research and Development
Page 47
Vancouver Design Center
Programming Notes and Examples
S1D13503
Issue Date: 01/01/30
X18A-G-002-06
6.
Determine the display memory location for image 2.
Place image 2 immediately after image 1 (see Figure 16). Assign the starting address for image 2 as follows:
Note that if the image 2 address is larger than D000:FFFFh, then switch to bank 1, reset the segment to D000h, and
keep the offset. For example, if the image 2 address were {D001:9200h, bank 0}, then this address must be changed
to {D000:9200h, bank 1}.
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:
AUX[08h] = 00h
AUX[09h] = 4Bh
8.
Program the Screen 1 Display Line Count Register.
The Display Line Count Register indicates how many lines of the first screen should be shown minus 1. By changing
the line count, image 2 appears to move up or down the display.
•
If the line count is set to the maximum number of visible scan lines - 1, only image 1 is shown.
AUX[0Ah] = LSB of (visible scan lines - 1) = EFh
AUX[0Bh] = MSB of (visible scan lines - 1) = 00h
•
If the line count is set to 0, then the first scan line of image 1 is shown followed by the first part of image 2. It is
not possible to show only image 2 by changing the line count. If only image 2 needs to be shown, reprogram the
Screen 1 Display Start Address Registers to point to the beginning of image 2. Once both Screen 1 and 2 Display
Start Address Registers point to the same image, the line count has no visible effect.
AUX[0Ah] = 00h
AUX[0Bh] = 00h
image 2 address
base display memory address
(
)
size of image 1
(
)
+
=
D000:0000h, bank 0
{
}
0000:9600h
+
=
D000:9600h, bank 0
{
}
=
Screen 2 Display Start Address
Screen 1 Display Start Address
size of image 1 in bytes
2 bytes per word
--------------------------------------------------------
+
=
0000h
9600h
2
---------------
+
4B00h
=
=
visible scan lines
1
–
240
1
–
239
00EFh
=
=
=
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