Epson S1D13705 technical manual Resource Management Issues

Epson Research and Development	Page 13
Vancouver Design Center

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 to 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.

Windows® CE 3.x Display Drivers	S1D13705
Issue Date: 01/05/25	X27A-E-006-01