Display Subsystem

Display Subsystem

Overview

The KN5000 uses a 320x240 color LCD driven by an MN89304 VGA-compatible controller. The display shows menus, parameters, song information, and graphical elements. Display updates are driven by the firmware’s main event loop (not by a vertical blank interrupt).

Architecture

┌─────────────────────────────────────────────────────────────┐
│                        MAIN CPU                              │
│                                                              │
│  Graphics routines in Main ROM                              │
│  UI framework manages pages and widgets                     │
│  Display updates in main event loop (not VBI)               │
└─────────────────────────────────────────────────────────────┘
                              │
                              v
┌─────────────────────────────────────────────────────────────┐
│                    MN89304 VGA CONTROLLER                    │
│                                                              │
│  Memory-mapped I/O: 0x1703B0-0x1703DF                       │
│  Resolution: 320 x 240 pixels                                │
│  Color depth: 8-bit indexed (256 colors)                    │
│  RAMDAC: 4-bit per channel (12-bit RGB)                     │
│  Row offset: svga_device::offset() << 3 (8x multiplier)    │
└─────────────────────────────────────────────────────────────┘
                              │
                              v
┌─────────────────────────────────────────────────────────────┐
│                 VIDEO RAM (0x1A0000-0x1DFFFF)               │
│                                                              │
│  256KB linear framebuffer                                    │
│  Active area: 76,800 bytes (320 x 240 x 1 byte/pixel)      │
│  Row stride: 320 bytes                                       │
└─────────────────────────────────────────────────────────────┘
                              │
                              v
┌─────────────────────────────────────────────────────────────┐
│                      LCD PANEL                               │
│                                                              │
│  320 x 240 color TFT LCD                                    │
│  Backlit display                                             │
└─────────────────────────────────────────────────────────────┘

MN89304 VGA Controller

The MN89304 is a VGA-compatible LCD controller with some important differences from standard VGA:

Key Differences from Standard VGA

Property	Standard VGA	MN89304 (KN5000)
DAC resolution	6-bit per channel (0-63)	4-bit per channel (0-15)
Palette color depth	18-bit RGB	12-bit RGB
Row pitch calculation	offset register value	offset << 3 (8x multiplier)
I/O base	CPU port space	Memory-mapped at 0x170000

VGA Register Map

VGA I/O ports are memory-mapped to CPU address 0x170000 + port_number:

VGA Port	CPU Address	Register	Access	Description
0x3C0	0x1703C0	Attribute Controller	W	Address/Data (alternating writes)
0x3C2	0x1703C2	Misc Output	W	Clock select, sync polarity
0x3C3	0x1703C3	VGA Enable	W	Global enable (write 0x01 to enable)
0x3C4	0x1703C4	Sequencer Index	W	Select sequencer register
0x3C5	0x1703C5	Sequencer Data	R/W	Sequencer register data
0x3C6	0x1703C6	DAC Mask	R/W	Palette mask (typically 0xFF)
0x3C7	0x1703C7	DAC Read Index	W	Select palette entry for reading
0x3C8	0x1703C8	DAC Write Index	W	Select palette entry for writing
0x3C9	0x1703C9	DAC Data	R/W	RGB data (3 sequential bytes per entry)
0x3CE	0x1703CE	Graphics Controller Index	W	Select GC register
0x3CF	0x1703CF	Graphics Controller Data	R/W	GC register data
0x3D4	0x1703D4	CRTC Index	W	Select CRTC register
0x3D5	0x1703D5	CRTC Data	R/W	CRTC register data
0x3DA	0x1703DA	Input Status 1	R	Vertical retrace status

VGA Initialization Values

The VGA_Setup routine (0xEF51A5) configures the full register set at boot. Key values:

Sequencer Registers (via ports 0x3C4/0x3C5):

Index	Value	Description
0x00	0x03	Reset (synchronous)
0x01	0x21	Clocking Mode (screen off during init; 0x01 = screen on)
0x02	0x0F	Map Mask (all 4 planes enabled)
0x03	0x00	Character Map Select
0x04	0x06	Memory Mode (chain-4, no odd/even)
0x06-0x11	various	MN89304 extended registers (LCD timing)

CRTC Timing Registers (via ports 0x3D4/0x3D5):

Index	Value	Description
0x00	0x65	Horizontal Total (101 chars)
0x01	0x27	Horizontal Display End (39 chars = 320px/8)
0x04	0x28	Start Horizontal Retrace
0x05	0x29	End Horizontal Retrace
0x06	0xF3	Vertical Total (243 lines)
0x07	0x00	Overflow
0x10	0xF2	Vertical Retrace Start (242)
0x11	0x03→0x80	Vertical Retrace End (unlock→lock CRTC 0-7)
0x12	0xEF	Vertical Display End (239 = 240 lines)
0x13	0x14	Offset (20 × 8 = 160 words = 320 bytes/row)
0x15	0xEF	Start Vertical Blanking
0x16	0xF3	End Vertical Blanking
0x17	0xE3	Mode Control
0x18	0xFF	Line Compare
0x19	0x00	MN89304-specific
0x1A	0x10	MN89304-specific

Graphics Controller (via ports 0x3CE/0x3CF):

Index	Value	Description
0x01	0x00	Enable Set/Reset
0x03	0x00	Data Rotate
0x04	0x00	Read Map Select
0x05	0x00	Graphics Mode
0x06	0x01	Miscellaneous (chain odd/even)
0x08	0xFF	Bit Mask

Misc Output: 0xE3 (25 MHz dot clock, negative H/V sync, 60 Hz)

Boot DAC Palette (9 basic colors):

Index	R	G	B	Color
0	0	0	0	Black
1	F	F	F	White
2	F	0	0	Red
3	0	F	0	Green
4	0	0	F	Blue
5	0	F	F	Cyan
6	F	F	0	Yellow
7	F	0	F	Magenta
8	0	0	4	Dark Blue

Palette Programming

The MN89304 uses a 4-bit RAMDAC (implemented as pal4bit() in MAME). Only the lower 4 bits of each color component value are significant:

// Writing a 256-color palette
for (int i = 0; i < 256; i++) {
    *(volatile uint8_t*)0x1703C8 = i;            // Select entry
    *(volatile uint8_t*)0x1703C9 = red[i] >> 4;  // 4-bit R (from 8-bit)
    *(volatile uint8_t*)0x1703C9 = green[i] >> 4; // 4-bit G
    *(volatile uint8_t*)0x1703C9 = blue[i] >> 4;  // 4-bit B
}

Palette data format notes:

• The HDAE5000 firmware stores palette data as 8-bit RGB and shifts right by 4 during loading
• If palette data is stored in 6-bit VGA format (0-63), shift right by 2 instead
• Effective color resolution: 4096 colors (16 levels per channel)

CRTC Start Address

The CRTC start address determines which VRAM byte appears at the top-left pixel:

CRTC Register	Index	Description
Start Address High	0x0C	High byte of VRAM start offset
Start Address Low	0x0D	Low byte of VRAM start offset

The firmware initializes the CRTC start address to 0x0000, meaning VRAM address 0x1A0000 corresponds to screen pixel (0,0).

// Reading current CRTC start address
*(volatile uint8_t*)0x1703D4 = 0x0C;
uint8_t start_high = *(volatile uint8_t*)0x1703D5;
*(volatile uint8_t*)0x1703D4 = 0x0D;
uint8_t start_low = *(volatile uint8_t*)0x1703D5;
uint16_t crtc_start = (start_high << 8) | start_low;

Row Offset Override

The MN89304 overrides the standard VGA row offset calculation with an 8x multiplier:

// In MAME: mn89304::offset()
uint32_t mn89304::offset() {
    return svga_device::offset() << 3;
}

This means the CRTC offset register value is multiplied by 8 to get the actual byte offset per row. The default configuration results in a 320-byte row stride (matching the 320-pixel width).

Video RAM

Property	Value
Base address	0x1A0000
Size	256KB (0x1A0000-0x1DFFFF)
Active display area	76,800 bytes (320 x 240)
Pixel format	8-bit indexed color (1 byte per pixel)
Row stride	320 bytes
Pixel addressing	VRAM_BASE + y * 320 + x

The framebuffer is linear and row-major. The active display occupies the first 76,800 bytes; the remaining ~185KB is unused but accessible.

Display Update Mechanism

Main Loop Driven (Not VBI)

The firmware’s display updates are not driven by a vertical blank interrupt. Instead, they occur as part of the main event loop at MainLoop:

Main Event Loop (MainLoop)
    |
    +-- Control Panel Poll
    +-- Display Update          <-- firmware draws its UI
    +-- MIDI Processing
    +-- FDC Handler
    +-- HDAE5000 Frame_Handler  <-- extension ROM callback
    +-- Audio Sync
    |
    (loop)

This means:

• Display updates happen at the main loop rate (not at a fixed refresh rate)
• The HDAE5000 Frame_Handler runs after the firmware’s display update
• Any VRAM writes by extension code will be overwritten on the next loop iteration unless the firmware’s drawing is disabled

Display Disable Flag

The firmware checks a flag byte at address 0x0D53 before performing display updates. Setting bit 3 of this byte disables all firmware-driven LCD rendering:

; At 0xEF77DF (main display update gate):
BIT 3, (0D53h)           ; Check display disable flag
JRL Z, skip              ; If bit 3 CLEAR, skip display entirely
CALL Display_ResetDirtyFlags
; ... dispatches via state byte (0D65h) ...
CALL Display_UpdateDirtyRegions

This check occurs at four firmware locations (0xEF77DF, 0xEFAA40, 0xF59C11, 0xF59D65), gating all display update code paths. When bit 3 is set, the firmware skips dirty-region tracking, state-based display dispatch, and VRAM writes — allowing an extension ROM to take full control of the framebuffer. See HDAE5000 Homebrew for usage details.

Workspace Display Callbacks

The firmware’s workspace dispatch system provides display-related callbacks accessible via Handler Table A:

Offset	Purpose	Notes
+0x0124	Display callback	Display state management
+0x0278	Display state	Display mode/state queries
+0x0534	Display update	Trigger display refresh

These callbacks are used by the original HDAE5000 firmware for integrating its UI with the main firmware’s display system. Their exact protocols are under investigation.

Drawing Primitives

The firmware implements a complete graphics library for rendering to offscreen buffers. All drawing targets OFFSCREEN_BUFFER_1 (0x43C00) by default, which is then blitted to VRAM (0x1A0000) during the display update cycle.

Rendering Pipeline

All drawing functions follow a deferred command queue pattern:

Caller invokes DrawLine/DrawBox/DrawString/etc.
     │
     ├── IS_XSP_INSIDE_4K_REGION_AT_1C032 (0xFAA532)
     │   checks if caller is running in the draw task context
     │   (stack pointer in range 0x1C032 - 0x1D032)
     │
     ├── YES (draw task context):
     │   Execute DrawXxx_Impl directly
     │   Write pixels to OFFSCREEN_BUFFER_1 (0x43C00)
     │   Call SetChangeRect() to expand dirty bounding box
     │
     └── NO (other task context):
         Serialize parameters into DrawQueue (circular buffer)
         Call DisplayCmd_DequeueAndExecute
         → TaskSched_WaitForEvent(3) until draw task picks up command
         → Draw task executes command and signals completion

This ensures all VRAM/buffer writes happen in a single task context, avoiding concurrency issues.

Draw Command Queue

The draw queue is a circular buffer managed by DrawQueue_Alloc (0xFAA4ED):

Property	Value
Base address	0x030466
Size	8KB (0x2000 bytes)
Write pointer	0x03246A
Read pointer	0x032474
Entry count	0x03247A (modular counter, wraps at 0x7C entries)
Synchronization	Event 3 (wait/signal) + Event 4 (audio lock)

Each queued command starts with a 4-byte function pointer (the DrawXxx_Impl address), followed by serialized parameters (8-28 bytes depending on the primitive). When the draw task processes a command, it calls the function pointer with the parameter block.

Graphics Initialization

InitializeGraphics (0xFAA4FA) performs the following at boot:

1. Initialize draw task (InitDrawTask)
2. Show screen group 5 and enable palette
3. Initialize palette RGB tables (InitPaletteRGB)
4. Set wallpaper (index 0) and palette (index 2)
5. Clear two offscreen buffers (each 0x9600 = 38,400 bytes) at 0x43C00 with Memset(0)

The two buffers at 0x43C00 and 0x4D200 (each 320x120 = 38,400 bytes) suggest a split-screen double-buffering scheme where the top and bottom halves of the 320x240 display are rendered independently.

Address Calculation

All drawing functions convert (x, y) pixel coordinates to buffer offsets using:

offset = y * 320 + x

The multiplication y * 320 is computed via shifts: (y << 2 + y) << 6 = y * 5 * 64. This is implemented in the shared helper Set_XWA_to_320_times_XDE at 0xEF5023.

Drawing Modes

Several primitives support multiple drawing modes specified by a mode code:

Mode	Code	Operation	Description
Write	0x201	pixel = color	Direct pixel write
Clear	0x202	pixel = 0x00	Clear pixel to zero
OR	0x203	pixel |= color	Bitwise OR with color
AND	0x204	pixel &= color	Bitwise AND with mask
XOR	0x205	pixel ^= color	Bitwise XOR (used for cursors, selection)

Special Colors

Color	Meaning
0xF7	Transparent (pixel skipped, no write)
0xF5	Read-back: reads pixel from secondary buffer (pattern fill)

Memory Operations

Function	Address	Description
Copy_DE_words_from_XBC_to_XWA	0xEF18D7	Block copy using LDIRW. Blits offscreen → VRAM
Fill_memory_at_XWA_with_DE_words_of_BC_value	0xEF18E0	Fill memory with 16-bit pattern (buffer clear)

Pixel Operations

Function	Address	Description
ReadPixel	0xFAA7B4	Read 8-bit color from offscreen buffer at (x, y)
ModifyPixel	0xFAA7E4	Write single pixel to offscreen buffer
ModifyPixelEx	0xFAA84A	Extended pixel op: write/clear/OR/AND/XOR modes

Rectangle Operations

Function	Address	Description
VRAM_FillRect	0xEF50DF	Fill 6×12 pixel rect directly in VRAM with solid color
DrawWall	0xFABB74	Fill entire screen from source buffer (wallpaper/splash)

Line Drawing

Function	Address	Description
DrawLine	0xFAA98A	Bresenham line from point A to point B
DrawLineEx	0xFAAA3E	Extended line with drawing mode (write/XOR/etc.)

Both use Bresenham’s algorithm with optimized fast paths for horizontal lines (dy = 0), vertical lines (dx = 0), and general diagonal lines. The color 0xF5 triggers pattern-fill mode where each pixel’s color is read from a secondary buffer instead of using a fixed color.

Bitmap/Sprite Drawing

The firmware uses a bitmap descriptor table in ROM at 0x913000. Each entry is 8 bytes:

+0x00: word  width (pixels)
+0x02: word  height (rows)
+0x04: long  pixel_data_ptr (24-bit address of pixel data in ROM)

Bitmap pixel data is stored as packed 16-bit words (2 pixels per word). Color 0xF7 in bitmap data is treated as transparent (pixel skipped).

Function	Address	Description
DrawBitmap	0xFABC3A	Draw bitmap with transparency (0xF7 = transparent)
DrawBitmapFast	0xFABE0E	Draw bitmap without transparency check (opaque only)
MovePixels	0xFABA60	Copy rectangular pixel block within offscreen buffer
Draw_FlashMemUpdate_message_bitmap	0xEF5040	Draw 224×22 monochrome (1bpp) bitmap for firmware update UI

Text Rendering

Text is rendered using a font glyph table in ROM at 0x945C00. Each font entry is 16 bytes:

+0x00: word  char_width (pixels per character)
+0x02: word  char_height (pixels)
+0x04: word  descent (below baseline)
+0x06: word  ascent (above baseline)
+0x08: long  glyph_bitmap_ptr (1bpp bitmap data, 8 pixels per byte, MSB first)
+0x0C: long  kerning_table_ptr (0 = fixed-width font; see below)

For variable-width fonts (kerning_table_ptr ≠ 0), the kerning table has 4-byte entries per character: {word char_width, word glyph_data_offset}. Each glyph uses ceil(char_width/8) × height bytes at glyph_bitmap_ptr + glyph_data_offset.

Character codes are offset by 0x20 (space) before table lookup. Glyphs are rendered as 1bpp bitmaps decomposed into 8-pixel-wide vertical strips, drawn left-to-right, top-to-bottom. All text rendering clips against a specified rectangle.

Function	Address	Description
DrawString	0xFACACE	Core text renderer: draws null-terminated string
DrawStringCentered	0xFACF17	Center text horizontally and vertically in rect
DrawStringLeftJustify	0xFACFBA	Left-align text (x = rect.left + 4), center vertically
DrawStringRightJustify	0xFAD004	Right-align text (x = rect.right - 4 - width)
DrawStringAlignment	0xFAD052	Dispatch by mode: 0=center, 1=left, 2=right
DrawStringReverse	0xFAD091	Draw with swapped fg/bg colors (selection highlight)

Font Helper Functions

Function	Address	Description
GetCharHeight	0xFB25ED	Return character height from font table (+0x02)
GetCharDescent	0xFB25F9	Return character descent from font table (+0x04)
CalcTotalWidth	0xFB270D	Calculate total pixel width of rendered string
ConvertStrings	0xFB264F	Convert control codes to displayable format (0x7E prefix = escape)
WordwrapStrings	0xFB26D2	Word-wrap text for multi-line layout

Character Encoding

Characters use ASCII encoding with an offset of 0x20 (space). Before lookup in the font or kerning table, each character code has 0x20 subtracted. Control characters below 0x20 are mapped to space.

Escape sequences: The 0x7E prefix byte introduces a two-digit hex-encoded character code:

0x7E 0x33 0x41  →  character 0x3A (colon)
0x7E 0x46 0x37  →  character 0xF7 (special symbol)

Hex digits support 0-9, a-f, and A-F.

Font Catalog

The firmware contains 10 fonts (IDs 0-9) in the Table Data ROM. Each font has 224 characters (ASCII 0x20-0xFF). All glyph data resides at 0x945C00-0x94FF00.

ID	Size	Type	Kerning	Description
0	8×16	Fixed	No	Standard UI font
1	8×16	Fixed	No	Standard UI font (bold variant)
2	16×16	Fixed	No	Wide/bold font (double-width)
3	6×8	Fixed	No	Small font (compact displays)
4	11×16	Fixed	No	Medium-wide font
5	var×16	Variable	Yes	Proportional font (widths 3-10px)
6	8×10	Fixed	No	Compact font (reduced height)
7	8×16	Fixed	No	Standard UI font (alternate style)
8	8×16	Fixed	No	Standard UI font (alternate bold)
9	11×16	Fixed	No	Medium-wide font (alternate)

Variable-width font (ID 5): Uses a kerning table at 0x94C620 with 4-byte entries per character: {word char_width, word glyph_offset}. Each glyph uses ceil(width/8) × height bytes. Character widths range from 3 to 10 pixels.

Font samples (extracted from ROM):

Font 0:

Font 1:

Font 2:

Font 3:

Font 4:

Font 5:

Font 6:

Font 7:

Font 8:

Font 9:

BDF (Bitmap Distribution Format) exports are available in the roms-disasm repository for use in emulators and tools.

Screen Layout and Regions

Region Architecture

The display is divided into 11 independently-tracked dirty regions. Each region has its own redraw function and dirty bit. The regions are not defined by hardcoded pixel coordinates — instead, each redraw function loads ROM descriptor tables that define the region geometry, content, and rendering parameters. These descriptors are passed to UI rendering helper functions.

Region Update Order

Display_UpdateDirtyRegions (0xEF5B36) updates regions in a specific order optimized for visual priority:

1. Region 0  - Status Bar         (mode indicators, tempo)
2. Region 5  - Menu Area          (menu/list content)
3. Region 7  - Parameter Display  (parameter names)
4. Region 8  - Value Display      (parameter values)
5. Region 9  - Indicator Area     (status indicators)
6. Region 1  - Title Bar          (song/patch name, up to 3 title fields)
7. Region 10 - Footer Area        (status/help text)
8. Region 6  - Button Labels      (soft button labels, 3 rows of 8)
9. Region 3  - Main Content       (primary display area)
10. Region 4 - Side Panel         (side parameters)
11. Region 2 - Selection          (highlight/cursor, drawn last for overlay)

Redraw Functions

Each region has a dedicated redraw function that references ROM descriptor tables:

Region	Redraw Function	Address	ROM Descriptors (examples)
0	Display_RedrawStatusBar	0xF00999	0xE0B905, 0xE0B92E, 0xE0B99D
1	Display_RedrawTitleBar	0xF00C89	0xE0BD52-0xE0BD7A (3 title fields)
2	Display_RedrawSelection	0xF00DA5	Variable (cursor overlay)
3	Display_RedrawMainContent	0xF00C33	0xE0BD89
4	Display_RedrawSidePanel	0xF00E35	Multiple descriptor sets
5	Display_RedrawMenu	0xEFF110	Complex menu rendering
6	Display_RedrawButtonLabels	0xF00FDC	0xE0C764, 0xE0C8CC, 0xE0BF6E
7	Display_RedrawParameters	0xEF6F1A	State-dependent
8	Display_RedrawValues	0xEF6FA3	State-dependent
9	Display_RedrawIndicators	0xEF704B	State-dependent
10	Display_RedrawFooter	0xF00C4A	0xE0BDAC, 0xE0BDE8, 0xE0BE06

Display State

The display state byte at address 0x0D65 (SFR 3429) selects the active screen mode:

Value	Mode
0	Default/normal display
2	Alternative layout (different descriptor sets used)

The state byte influences which ROM descriptors are selected by redraw functions, allowing the same regions to display different content based on the active screen mode.

UI Rendering Helpers

The redraw functions delegate to specialized rendering helpers:

Helper	Address	Purpose
Scoop_EventLoop_12Entry	0xF0212C	General UI element renderer
GraphicsRender_Start	0xFB15F6	Two-descriptor pair renderer
GraphicsRender_ProcessEntries	0xFB1594	Simple descriptor renderer
Scoop_CurveUpdate_SegmentEnd	0xF01930	Content area renderer
Scoop_GlideParam_Setup	0xF01DAB	Number/value display renderer
Scoop_EventLoop_36Entry	0xF023CF	Dynamic value renderer
DrawFunc_Init	0xFB2044	Parameter display renderer
ColorBlit_WithPaletteSave	0xFB24CB	Status indicator renderer

Button Label Organization

Region 6 (button labels) manages three rows of 8 soft-button labels, organized at RAM addresses:

• Row 1: 0x0E55 (8 entries, 4 bytes apart)
• Row 2: 0x0E75 (8 entries, 4 bytes apart)
• Row 3: 0x0E95 (8 entries, 4 bytes apart)

Dirty Region Tracking

The display update system tracks 11 independent screen regions. Each region has a dirty bit in the bitmap at DISPLAY_DIRTY_FLAGS (0x205E4):

Function	Address	Description
Display_ResetDirtyFlags	0xEF5B27	Clear all dirty flags and enable flag
Display_UpdateDirtyRegions	0xEF5B36	Check all 11 regions, call redraw for dirty ones
Display_UpdateRegion0	0xEF5B8B	Status bar
Display_UpdateRegion1	0xEF5BE9	Title bar
Display_UpdateRegion2	0xEF5C20	Selection highlight
Display_UpdateRegion3	0xEF5C07	Main content area
Display_UpdateRegion4	0xEF5C39	Side panel
Display_UpdateRegion5	0xEF5C52	Menu area
Display_UpdateRegion6	0xEF5C6B	Button labels
Display_UpdateRegion7	0xEF5C84	Parameter display
Display_UpdateRegion8	0xEF5C9D	Value display
Display_UpdateRegion9	0xEF5CB6	Indicator area
Display_UpdateRegion10	0xEF5CCF	Footer area

Change Tracking

Function	Address	Description
SetChangeRect	0xFAA760	Expand dirty bounding box to include drawn region

The bounding box is maintained at:

Address	Purpose
0x030456	Min X (left edge)
0x030458	Min Y (top edge)
0x03045A	Max X (right edge)
0x03045C	Max Y (bottom edge)
0x03045E	Update flag (non-zero = needs refresh)

Offscreen Buffers

Buffer	Address	Size	Purpose
OFFSCREEN_BUFFER_1	0x043C00	76,800 bytes	Primary render target (all drawing goes here)
OFFSCREEN_BUFFER_2	0x056800	76,800 bytes	Secondary buffer (scrolling/animation)
OFFSCREEN_BUFFER_3	0x05FE00	76,800 bytes	Tertiary buffer (compositing)
OFFSCREEN_BUFFER_4	0x069400	76,800 bytes	Quaternary buffer (sprites/overlays)

UI Widget Rendering

Rectangle & Shape Primitives

In addition to the pixel-level drawing primitives, the firmware provides higher-level shape drawing functions:

Function	Address	Description
DrawBox	0xFAB295	Fill a rectangle with solid color (clip to 0-319, 0-239)
DrawFrame	0xFAB400	Draw rectangle outline (4 border lines, no fill)
DrawFrameEx	0xFAB8CC	Styled frame with XOR support and screen clipping
DrawDesignFrame	0xF9C8B7	Decorative frame with special border patterns
DrawDesignBox	0xFAD559	Styled box with type-specific rendering

Icon Rendering

The firmware maintains a separate icon descriptor table at 0x938000 (in Table Data ROM), using the same 8-byte format as the bitmap table:

Function	Address	Description
DrawIcons	0xFABF61	Draw icon from table at 0x938000
DrawBitmapSP	0xFAC0CB	Draw bitmap with special color mapping
DrawBitmapSPFast	0xFAC1FF	Fast special bitmap rendering
DrawBitmapSP2	0xFAC38D	Alternative special bitmap variant
DrawBitmapFile	0xFAC3FB	Draw bitmap from file/external data

Progress Bar Widgets

Function	Address	Description
DrawProgressRectH	0xF99E75	Horizontal progress bar (3 modes: center, left, right fill)
DrawProgressRectV	0xF99F7D	Vertical progress bar (3 modes: center, top, bottom fill)

Widget Event Handlers

The firmware implements widget-specific event handlers following a *Proc naming convention:

Widget Type	Handler	Description
GroupBox	GroupBoxProc	Container/panel widget
Label	LabelProc	Static text display
EditSwitch	EditSwProc	Toggle/checkbox control
TextBox	TextBoxProc	Text input field

Many domain-specific widget types exist for the keyboard’s various modes (arrangement, composition, bank selection, etc.).

LCD Control

Function	Address	Description
LcdOn	0xFAA5D0	Enable LCD output (set flag at 0x030464)
LcdOff	0xFAA5DB	Disable LCD output
ChangePalette	0xFAF34E	Switch color palette
ChangeWall	0xFAF21C	Load background wallpaper
ChangeWallPalette	0xFAF26C	Change palette for wallpaper

Embedded Images

Images extracted from firmware ROMs:

Source	Count	Description
Main CPU ROM	42	UI elements, logos, demo graphics
HDAE5000 ROM	4	Product logo, file panel graphics

See Image Gallery for all extracted images.

Display Modes

The KN5000 uses a single display mode:

Property	Value
Width	320 pixels
Height	240 pixels
Color Depth	8-bit (256 color palette)
RAMDAC	4-bit per channel (12-bit effective RGB)
Refresh	Main-loop driven (not fixed rate)

Related Pages

• HDAE5000 Homebrew Development - Display ownership for custom ROMs
• Image Gallery - Extracted firmware graphics
• UI Framework - Menu and widget system
• Hardware Architecture - Physical components
• System Overview - Overall architecture

Animation and Transition Effects

The KN5000 implements several animation and transition effect mechanisms, all software-based (no hardware scroll registers are used).

Rendering Pipeline

All drawing operations target OFFSCREEN_BUFFER_1 (0x43C00), never VRAM directly. The UpdateScreen function (0xFAA61D) copies changed regions to VRAM:

Drawing Operation (DrawString, DrawBox, etc.)
        ↓
Write to OFFSCREEN_BUFFER_1 (0x43C00)
        ↓
Call SetChangeRect() → expand dirty bounding box at 0x030456
        ↓
Main loop calls UpdateScreen (0xFAA61D)
        ↓
Check dirty bounding box:
  Full screen? → full-screen blit (0xFB30A9)
  Partial?     → row-by-row blit (0xFB30D3)
        ↓
Copy from 0x43C00 → VRAM at 0x1A0000
        ↓
Reset dirty box and flags

During large updates, VGA_ScreenBlank (0xFB319A) blanks the display by setting VGA Sequencer register 01h bit 5, preventing visible tearing. VGA_ScreenUnblank (0xFB318A) re-enables display after the update.

Palette-Based Fade Effects

The firmware implements fade effects through VGA DAC palette manipulation:

Function	Address	Description
ChangePalette	0xFAF2F3	Switch to a new 256-color palette from table at 0xEAAE66
PaletteBankRotation	0xFAF346	Rotate pixel values through palette banks for fade effect

Palette table at 0xEAAE66: entries are 10 bytes each, containing pointers to RGB palette data. The firmware supports 16 palette banks of 16 colors each (0x00-0x0F through 0xE0-0xEF).

Palette bank rotation (0xFAF346) creates fade effects by modifying pixel color indices:

• Pixels with value >= 0xE0: subtract 0x90 (wrap to lower bank)
• Pixels with value < 0xE0: add 0x10 (shift to next bank)

This rotates all pixels one palette bank forward. Combined with palettes arranged as intensity gradients, this produces smooth brightness fade transitions.

Key palette state addresses:

Address	Purpose
0x03EF94	Current palette data pointer
0x03EF9E	Current palette index
0x03EFA0	Previous palette index (for partial updates)
0x030460	Palette update pending flag

Grid-Based Screen Transitions

Complex screen transitions use a grid-based dissolve effect:

Function	Address	Description
AcFadeSetGridBoxProc	0xF7514A	Grid fade effect processor (event-driven)
FadeSetGridCheck	0xF75377	Grid parameter validation and dispatch
TtFadeInOut	0xF75118	Fade-in/out state machine (Entertainer mode)

The grid effect divides the screen into cells and fades them individually with staggered timing, creating a “dissolve” appearance. Configuration uses ROM lookup tables:

• 0xE7F948 — fade-in timing table
• 0xE7F956 — fade-out timing table
• 0xE7F964 — jump table for 7 sub-handlers (events 0x17-0x1D)

Pre-Computed Fade Data

Four binary data blobs in ROM store pre-computed fade transition patterns:

Label	Address	Size	Purpose
Bitmap_FadeInPicture	0xEB8072	2800	Picture fade-in transition data
Bitmap_FadeInText	0xEB8B62	1440	Text fade-in transition data
Bitmap_FadeOutPicture	0xEB9102	2850	Picture fade-out transition data
Bitmap_FadeOutText	0xEB9C24	2160	Text fade-out transition data

Timer-Driven Animation

Animation timing is handled by the IvOneShotTimerProc (0xF8A122) event handler, which provides single-shot timer callbacks for UI animation frame ticks.

Screen Transition State Machine

The SeqState_TransitionMode (0xF99579) handler manages full-screen mode transitions (e.g., switching between sequencer screens, entering demo mode). It coordinates state variables at:

• 0x02749A — transition progress counter
• 0x02749E — transition timer
• 0x0274A2 — transition type/flags
• 0x0274A8-0x0274AE — additional transition parameters

Scrolling

All scrolling is software-based — no VGA hardware scroll registers are used. Scrolling is implemented via MovePixels (0xFABA60), which copies rectangular pixel blocks within the offscreen buffer. The AcRotStrBoxProc (0xF8D6D8) handler provides smooth scrollbar animation with timer-based auto-repeat.

UI element names “SlideMove” and “SlideBase” appear in the firmware’s string table (0xEAB8D8), suggesting slide animation support for UI transitions.

MAME Emulation Status

Component	Status	Notes
MN89304 VGA Controller	Working	Register map emulated, 320×240 8bpp LCD output
VRAM	Working	256KB at 0x1A0000-0x1DFFFF, linear framebuffer
Palette	Working	256-color palette with 4-bit RAMDAC (VGA DAC at 0x170000)
Display output	Working	Full screen rendering visible, UI widgets draw correctly
Font rendering	Working	All firmware text drawing functions operate correctly
Page transitions	Partial	Palette fade works; grid dissolve not verified

The display is one of the most complete subsystems in MAME emulation. The MN89304 VGA controller is emulated as a custom device with the KN5000-specific RAMDAC and offset override behaviors.

Research Needed

• Document VGA register map at 0x170000 — Complete: full register set with init values
• Document VGA initialization sequence (boot-time register programming) — Complete
• Analyze framebuffer memory layout
• Understand display update mechanism (main loop, not VBI)
• Document MN89304 differences from standard VGA (4-bit RAMDAC, offset override)
• Identify display disable mechanism (0x0D53 bit 3)
• Identify font rendering routines (DrawString family, font table at 0x945C00)
• Document text drawing functions (DrawString, Centered, Left/Right, Reverse, Alignment)
• Map UI widget drawing primitives (pixel, line, rect, bitmap, text, blit)
• Document page transition effects (palette fade, grid dissolve, state machine)
• Document deferred draw command queue – Complete: DrawQueue circular buffer, task context check, synchronization
• Document workspace display callbacks (0x0124, 0x0278, 0x0534) protocols
• Reverse engineer pre-computed fade data format (BitmapFadeIn/Out blobs)

Code References

Core Display

Symbol	Address	Purpose
Display_ResetDirtyFlags	0xEF5B27	Clear all dirty flags
Display_UpdateDirtyRegions	0xEF5B36	Check and redraw dirty regions
UpdateScreen	0xFAA61D	Copy changed regions to VRAM
Set_XWA_to_320_times_XDE	0xEF5023	Y×320 coordinate calculation
VGA_ScreenBlank	0xFB319A	Blank display during updates
VGA_ScreenUnblank	0xFB318A	Restore display after updates
LcdOn	0xFAA5D0	Enable LCD output
LcdOff	0xFAA5DB	Disable LCD output
DrawQueue_Alloc	0xFAA4ED	Allocate space in deferred draw queue
DisplayCmd_DequeueAndExecute	0xFAA36A	Process queued draw command in draw task
IS_XSP_INSIDE_4K_REGION_AT_1C032	0xFAA532	Check if caller runs in draw task context
InitializeGraphics	0xFAA4FA	Boot-time graphics initialization
DrawFunc	0xFAA48C	Generic draw function dispatch with deferred support

Drawing Primitives

Symbol	Address	Purpose
ReadPixel	0xFAA7B4	Read pixel from offscreen buffer
ModifyPixel	0xFAA7E4	Write single pixel
ModifyPixelEx	0xFAA84A	Write/clear/OR/AND/XOR pixel
DrawLine	0xFAA98A	Bresenham line drawing
DrawLineEx	0xFAAA3E	Line with drawing mode
DrawBox	0xFAB295	Filled rectangle
DrawFrame	0xFAB400	Rectangle outline
DrawFrameEx	0xFAB8CC	Styled frame with XOR
VRAM_FillRect	0xEF50DF	Direct VRAM rectangle fill
SetChangeRect	0xFAA760	Expand dirty bounding box
Copy_DE_words_from_XBC_to_XWA	0xEF18D7	Block memory copy (blit)

Bitmap & Sprite

Symbol	Address	Purpose
DrawBitmap	0xFABC3A	Bitmap with transparency (0xF7)
DrawBitmapFast	0xFABE0E	Opaque bitmap (no transparency)
DrawIcons	0xFABF61	Icon from table at 0x938000
MovePixels	0xFABA60	Copy rectangular pixel block
DrawWall	0xFABB74	Full-screen wallpaper fill
Draw_FlashMemUpdate_message_bitmap	0xEF5040	1bpp update UI bitmap renderer

Text

Symbol	Address	Purpose
DrawString	0xFACACE	Core text renderer
DrawStringCentered	0xFACF17	Center-aligned text
DrawStringLeftJustify	0xFACFBA	Left-aligned text
DrawStringRightJustify	0xFAD004	Right-aligned text
DrawStringReverse	0xFAD091	Reversed fg/bg colors
CalcTotalWidth	0xFB270D	Calculate string pixel width

Display Regions

Symbol	Address	Purpose
Display_RedrawStatusBar	0xF00999	Region 0: Status bar
Display_RedrawTitleBar	0xF00C89	Region 1: Title bar
Display_RedrawSelection	0xF00DA5	Region 2: Selection highlight
Display_RedrawMainContent	0xF00C33	Region 3: Main content
Display_RedrawSidePanel	0xF00E35	Region 4: Side panel
Display_RedrawMenu	0xEFF110	Region 5: Menu area
Display_RedrawButtonLabels	0xF00FDC	Region 6: Button labels
Display_RedrawParameters	0xEF6F1A	Region 7: Parameter display
Display_RedrawValues	0xEF6FA3	Region 8: Value display
Display_RedrawIndicators	0xEF704B	Region 9: Indicators
Display_RedrawFooter	0xF00C4A	Region 10: Footer

Palette & Effects

Symbol	Address	Purpose
ChangePalette	0xFAF34E	Switch color palette
ChangeWall	0xFAF21C	Load wallpaper
PaletteBankRotation	0xFAF346	Fade via palette bank rotation
AcFadeSetGridBoxProc	0xF7514A	Grid dissolve transition
SeqState_TransitionMode	0xF99579	Full-screen mode transition
DrawProgressRectH	0xF99E75	Horizontal progress bar
DrawProgressRectV	0xF99F7D	Vertical progress bar

How to Contribute

See Help Wanted for contribution guidelines.

The HDAE5000 ROM has documented VGA palette setup at 0x28F8E0 which can serve as a reference for understanding the display interface.