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Page 34 Epson Research and Development
Vancouver Design Center
S1D13705 Programming Notes and Examples
X27A-G-002-03 Issue Date: 02/01/22
5.3.2 Examples
Example 5:Display 200 scanlines of image 1 and 40 scanlines of image 2. Image 2 is
located first (offset 0) in the display buffer followed immediately by im-
age 1. Assume a 320x240 display and a color depth of 4 bpp.
1. Calculate the Screen 1Vertical Size register values.
vertical_size = 200 = C8h
Write the Vertical Size LSB, REG[12h], with C8h and Vertical Size MSB, REG[13h],
with a 00h.
2. Calculate the Screen 1 Start Word Address register values.
Screen 2 is located first in display memory, therefore we must calculate the number of
bytes taken up by the screen 2 data.
bytes_per_line = pixels_per_line / pixels_per_byte = 320 / 2 = 160
total bytes = bytes_per_line x lines = 160 x 40 = 6400.
Screen 2 requires 6400 bytes (0 to 6399) therefore the start address offset for screen 1
must be 6400 bytes. (6400 bytes = 3200 words = C80h words)
Set the Screen 1 Start Word Address MSB, REG[0Dh], to 0Ch and the Screen 1 Start
Word Address LSB, REG[0Ch], to 80h.
3. Calculate the Screen 2 Start Word Address register values.
Screen 2 display data is coming from the very beginning of the display buffer. All there is
to do here is ensure that both the LSB and MSB of the Screen 2 Start Word Address
registers are set to zero.