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Vancouver Design Center
Windows® CE 3.x Display Drivers S1D13705
Issue Date: 01/05/25 X27A-E-006-01
Resource Management Issues
The Windows CE 3.0 OEM must deal with certain display driver issues relevant to
Windows CE 3.0. These issues require the OEM balance factors such as: system vs. display
memory utilization, video performance, and power off capabilities.
The section “Simple Display Driver Configuration” on page 15 provides a configuration
which should work with most Windows CE platforms. This section is only intended as a
means of getting started. Once the developer has a functional system, it is recommended to
optimize the display driver configuration as described below in “Description of Windows
CE Display Driver Issues”.
Description of Windows CE Display Driver Issues
The following are some issues to consider when configuring the display driver t o work with
Windows CE:
1. When Windows CE enters the Suspend state (power-off), the LCD controller and dis-
play memory may lose power, depending on how the OEM sets up the system. If dis-
play memory loses power, all images stored in display memory are lost.
If power-off/power-on features are required, the OEM has several options:
• If display memory power is turned off, add code to the display driver to save any
images in display memory to system memory before power-off, and add code to
restore these images after power-on.
• If display memory power is turned off, instruct Windows CE to redraw all images
upon power-on. Unfortunately it is not possible to instruct Windows CE to redraw
any off-screen images, such as icons, slider bars, etc., so in this case the OEM
must also configure the display driver to never use off-screen memory.
• Ensure that display memory never loses power.
2. Using off-screen display memory significantly improves display performance. For ex-
ample, slider bars appear more smooth when using off-screen memory. To enable or
disable the use of off-screen memory, edit the file: x:\wince300\platform\cepc\driv-
ers\display\S1D13705\sources. In SOURCES, there is a line which, when uncom-
mented, will instruct Windows CE to use off-screen display memory (if sufficient
display memory is available):
CDEFINES=$(CDEFINES) -DEnablePreferVmem
3. In the file PROJECT.REG under CE 3.0, there is a key called PORepaint (search the
Windows CE directories for PROJECT.REG). PORepaint is relevant when the Sus-
pend state is entered or exited. PORepaint can be set to 0, 1, or 2 as described below:
a. PORepaint=0
• This mode tells Windows CE not to save or restore display memory on sus-
pend or resume.