Framebuffer¶

The BE-300 display is a 320x240 color STN LCD panel driven by an EPSON L50753 controller, with video memory mapped through the VRC4173 companion chip.

Display Specifications¶

Parameter	Value
Resolution	320 x 240 pixels
Color Depth	16 bits per pixel
Color Format	RGB 5:6:5 (default) or RGB 5:5:5
LCD Controller	EPSON L50753
Panel Type	Color STN

Video Memory Layout¶

Parameter	Value
Base Address	PA 0x0A200000 (kseg1: 0xAA200000)
Pixel Size	2 bytes (16 bits)
Line Stride	512 bytes
Active Pixels per Line	320 (640 bytes)
Padding per Line	192 bytes (unused)
Total Framebuffer	240 x 512 = 122,880 bytes (~120 KB)

Pixel Address Formula¶

pixel_address = 0xAA200000 + (row * 512) + (col * 2)

Where row ranges from 0 to 239 and col ranges from 0 to 319.

Pixel Format¶

Each pixel is stored as a 16-bit little-endian value:

RGB 5:6:5 (Default)¶

Bit: 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
      R  R  R  R  R  G  G  G  G  G  G  B  B  B  B  B

Component	Bits	Range
Red	15:11	0-31
Green	10:5	0-63
Blue	4:0	0-31

RGB 5:5:5 (Alternate)¶

Some display modes use 5 bits per channel with bit 15 unused:

Bit: 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
      X  R  R  R  R  R  G  G  G  G  G  B  B  B  B  B

5-Bit Green Mode

The Linux 2.6 kernel uses RGB 5:5:5 format. When running vmlinux-2.6 in the emulator, use the --sfb-5bit-green flag for correct colors.

WinCE Display Rendering¶

Windows CE renders the "Starting..." and "Initializing..." splash screens at runtime using the GWE (Graphics, Windowing, and Events) subsystem. These strings are not stored as bitmaps or text in NK.exe -- they are rendered through font rendering into framebuffer scratch areas.

OAL Display Function (0x80078E10)¶

The OAL display blit dispatcher accepts a mode parameter in $a0:

Mode ($a0)	Action
0	Blit splash buffer from VA 0x80061188 to framebuffer
6	Blit 240x160 pixel buffer from VA 0x80061CD0 (progress bar)
10	Clear screen (fill framebuffer with solid color)

The splash buffers at 0x80061188 and 0x80061CD0 are zero-filled in the NK.exe binary. GWE populates them at runtime after the display driver is initialized.

Framebuffer in Linux¶

The Linux kernels use a simple framebuffer driver that maps the video memory directly. The framebuffer console (console=tty0) renders text using a built-in font. PicoGUI uses the framebuffer for its windowing system.