sed1355 ETC-unknow, sed1355 Datasheet - Page 183

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

Epson Research and Development
Vancouver Design Center
5.2.2 Examples
Programming Notes and Examples
Issue Date: 99/04/27
Note
For the examples in this section assume that the display system has been set up to view a 640x480
pixel image in a 320x240 viewport. Refer to Section 2, “Initialization” on page 8 and Section 5.1,
“Virtual Display” on page 23 for assistance with these settings.
Example 3: Panning - Right and Left
To pan to the right, increment the pixel pan value. If the pixel pan value is equal to the current color
depth then set the pixel pan value to zero and increment the start address value. To pan to the left
decrement the pixel pan value. If the pixel pan value is less than zero set it to the color depth (bpp)
less one and decrement the start address.
The following pans to the right by one pixel in 4 bpp display mode.
1.
2.
3.
Example 4: Scrolling - Up and Down
To scroll down, increase the value in the Screen 1 Display Start Address Register by the number of
words in one virtual scan line. To scroll up, decrease the value in the Screen 1 Display Start Address
Register by the number of words in one virtual scan line.
Scrolling operations are easier to follow if a value, call it pan_value, is used to track both the pix-
el pan and start address. The least significant bits of pan_value will represent the pixel pan value
and the more significant bits are the start address value.
This is a pan to the right. Increment pan_value.
pan_value = pan_value + 1
Mask off the values from pan_value for the pixel panning and start address register portions. In
this case, 4 bpp, the lower two bits are the pixel panning value and the upper bits are the start
address.
pixel_pan = pan_value AND 3
start_address = pan_value SHR 3
Write the pixel panning and start address values to their respective registers using the proce-
dure outlined in the registers section.
(the fist two bits of the shift account for the pixel_pan
the last bit of the shift converts the start_address value
from bytes to words)
X23A-G-003-05
SED1355
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