SPC8104 S-MOS Systems, SPC8104 Datasheet - Page 144

• Manufacturer Part Number: SPC8104
• Description: VGA LCD CONTROLLER
• Manufacturer: S-MOS Systems

8.0
The SPC8104F0A BIOS has been made to be as flexible as possible. To aid software develop-
ment on small panel sizes, we have incorporated special mode numbers for the most common
vertical resolutions so drivers for programs such as Windows can use the panel appropriately. In
addition to these changes, there are many limitations to running a small panel that should be
mentioned.
Running VGA software on a small panel poses a couple of problems. These problems are viewing
area and software compatibility. In addition, special non-standard IBM modes must be supported
to aid in application development.
8.1
To support each small panel, the panel type must be selected using the MD0-MD3, and MD9 pin
polarities as an index into a list of supported panels. Seiko Epson has chosen the most common
vertical resolutions on small panels and designed planar graphics modes for these. They are as
follows:
Once a vertical panel resolution is selected, the BIOS will set the physical panel size and will try
to accommodate running standard IBM modes on this panel. The BIOS modifies standard CRTC
timings and line doubling to get as much information on the small panel as possible for these IBM
standard modes. In addition the BIOS also supplies the planar graphics modes listed above to
help an OEM develop custom software. Note that the horizontal width of these resolutions
defaults to 640 pixels wide, which can be adjusted after the mode is set.
Viewing Area
The major problem with small form factor panels, is that IBM defined its VGA modes around two
basic resolutions: 640 x 480 and 720 x 400. To get the information presented in these modes onto
the smaller panels, we have some workarounds which are different for Text and Graphics modes,
however each has its limitations.
Standard VGA text mode displays 80 x 25 characters on a 720 x 400 monitor. To display the same
information on a small panel, we force 720 text modes to 640 using an 8-dot clock; unfortunately
in the horizontal this is all we can do, therefore if a panel is smaller than 640 dots wide we will
truncate information. However, our solutions for getting more information in the vertical direction
is much more flexible. For panel sizes less than 400 lines, we have chosen to use 8 pixel high
characters instead of the regular 16 pixel high characters, so that at least 25 lines can be visible
on the screen. For panel sizes 400 lines or greater, we can still use the normal 16 pixel high font
and see everything on the screen.
BIOS Functional Specification
SP2-38
Text Modes
SMALL FORM FACTOR PANEL SUPPORT ISSUES
Special Mode Support
Resolution
S-MOS Systems, Inc. • Tel: [phone] • Fax: [phone] • http://www.smos.com
200
240
256
320
400
Mode No.
41H
42H
43H
44H
45H
X15-SP-002-03
412-1.0
SPC8104