; SPDX-FileCopyrightText: 2024-2026 Zayn Otley ; SPDX-License-Identifier: AGPL-3.0-or-later ; See LICENSES/AGPL-3.0-or-later.txt. ; ============================================================================ ; ANTIC PLASMA DEMO - Raster Bars with Vertical Sine Scrolltext and SID Music ; x86 Assembly for Intuition Engine - ANTIC Display List + GTIA Colour ; ============================================================================ ; ; === SDK QUICK REFERENCE === ; Target CPU: x86 (16/32-bit Intel-compatible) ; Video Chip: ANTIC (Atari-inspired IE-native display list) + GTIA ; Audio Engine: SID (Commodore 64 sound chip, MOS 6581/8580) ; Assembler: ie32asm (x86 mode) ; Build: (cd sdk/examples/asm && nasm -f bin -I ../../include/ -o antic_plasma_x86.ie86 antic_plasma_x86.asm) ; Porting: ANTIC/GTIA MMIO is CPU-agnostic. Display list programming ; works the same from any CPU core. SID audio setup is also ; identical across all IntuitionEngine architectures. ; ; === WHAT THIS DEMO DOES === ; 1. Displays animated plasma "raster bars" using per-scanline colour changes ; 2. Shows two vertical sine-wave scrolltexts using Player/Missile graphics ; 3. Uses the IE-native ANTIC display list (similar to Amiga copper lists) ; 4. Plays SID music through the Commodore 64 audio emulation ; ; === ANTIC DISPLAY LIST ARCHITECTURE === ; ANTIC (Alpha-Numeric Television Interface Controller) was designed by ; Jay Miner for the Atari 400/800 in 1979. It was the first consumer ; display processor to use a programmable "display list" - essentially a ; small program stored in memory that tells the chip how to render each ; group of scanlines. This was revolutionary because it allowed mixed-mode ; displays (text and graphics on the same screen), variable resolution per ; zone, and fine scrolling - far more flexible than the fixed display ; formats of the Apple II or TRS-80. ; ; GTIA (George's Television Interface Adapter) was ANTIC's companion chip. ; While ANTIC controlled timing and display list execution, GTIA handled ; the actual colour output (128 colours: 16 hues x 8 luminances) and ; player/missile (sprite) graphics. This demo makes extensive use of both ; chips: ANTIC for display list timing and WSYNC synchronisation, GTIA for ; per-scanline background colours and Player/Missile scrolltext rendering. ; ; In the IntuitionEngine, ANTIC is Atari-inspired but IE-native. The display ; list is stored in memory and processed by the video chip each frame; this ; demo uses a mostly blank display list while CPU WSYNC writes drive bars. ; ; === THESE EFFECTS MATTER (HISTORICAL CONTEXT) === ; ; PLASMA EFFECTS: ; "Plasma" refers to smoothly animated colour patterns created by combining ; multiple sine waves. On 8-bit hardware, these were computed in real-time ; using lookup tables. The effect creates an organic, flowing appearance ; that was impressive on hardware with limited colour palettes. ; ; PLAYER/MISSILE GRAPHICS (P/M): ; Atari's hardware sprites are called "players" (8 pixels wide) and ; "missiles" (2 pixels wide). Unlike software sprites, they do not require ; erasing/redrawing - just update position registers and graphics data. ; This demo uses all 4 players for two dual-character scrolltexts. ; ; VERTICAL SCROLLING WITH SINE WAVE: ; Classic demoscene effect where text scrolls vertically through the screen ; while each character wobbles horizontally following a sine wave pattern. ; This creates a "wavy" or "rubbery" text effect popular in Amiga and ; Atari demos of the late 1980s and early 1990s. ; ; === x86 FOR AN ATARI DEMO? === ; The original Atari 8-bits used a 6502 CPU at 1.79 MHz. This demo runs on ; the IntuitionEngine's 32-bit x86 core, demonstrating that: ; 1. The ANTIC/GTIA emulation works correctly with any CPU architecture ; 2. Modern 32-bit maths makes plasma calculations trivial (vs 8-bit) ; 3. You can mix retro video hardware with modern CPU capabilities ; ; On a real 6502, this plasma effect would require extensive optimisation, ; pre-calculated tables, and careful cycle counting. On x86, we can use ; IMUL instructions and 32-bit registers freely. ; ; === ARCHITECTURE OVERVIEW === ; ; +-------------------------------------------------------------+ ; | MAIN LOOP (~60 FPS) | ; | | ; | +-----------+ +-----------+ +-------------------+ | ; | | WAIT FOR |--->| UPDATE |--->| WAIT FOR ACTIVE | | ; | | VBLANK | | TIME | | DISPLAY | | ; | +-----------+ +-----------+ +-------------------+ | ; | | | ; | +---------------------------------------------+ | ; | | PER-SCANLINE LOOP (192x) | | ; | | +----------+ +----------+ +-----------+ | | ; | | | COMPUTE | | DRAW | | WSYNC | | | ; | | | PLASMA | | SCROLLERS| | (sync to | | | ; | | | COLOUR | | (P/M gfx)| | scanline) | | | ; | | +----------+ +----------+ +-----------+ | | ; | +---------------------------------------------+ | ; +-------------------------------------------------------------+ ; ; +-------------------------------------------------------------+ ; | ANTIC DISPLAY LIST (runs in parallel) | ; | | ; | The ANTIC chip reads and executes the display list program | ; | independently of the CPU. It specifies: | ; | - How many blank lines (borders) | ; | - Which graphics mode for each line | ; | - Where screen memory is located (LMS instruction) | ; | - When to trigger Display List Interrupts (DLI) | ; | - When to jump back and wait for vertical blank (JVB) | ; +-------------------------------------------------------------+ ; ; +-------------------------------------------------------------+ ; | SID AUDIO ENGINE (runs in parallel) | ; | | ; | The SID emulation plays Commodore 64 music files | ; | independently. Once started, it synthesises audio without | ; | any CPU intervention, freeing us for graphics work. | ; +-------------------------------------------------------------+ ; ; === REGISTER USAGE === ; ESI - Time counter 1 (plasma wave animation) ; EDI - Time counter 2 (plasma wave animation, different speed) ; ECX - Current scanline number (0-191) during rendering ; EAX, EBX, EDX, EBP - Scratch registers for calculations ; ; === MEMORY MAP === ; 0x000000 Program entry point (org 0) ; 0xFF0000 Stack top (grows downward) ; 0xF2100-0xF213F ANTIC registers (DMACTL, display list ptr, WSYNC, etc.) ; 0xF2140-0xF21FB GTIA registers (COLBK, COLPM, HPOSP, GRAFP, collisions) ; 0xF0E00-0xF0E2F SID registers (voices, filter, player control) ; display_list ANTIC display list program (in .data section) ; sin_table 256-byte sine lookup table ; font_data 8x8 bitmap font (ASCII 32-95) ; sid_data Embedded SID music file ; ; === BUILD AND RUN === ; (cd sdk/examples/asm && nasm -f bin -I ../../include/ -o antic_plasma_x86.ie86 antic_plasma_x86.asm) ; ; (c) 2024-2026 Zayn Otley - GPLv3 or later ; ============================================================================ bits 32 ; 32-bit protected mode code org 0 ; Code starts at address 0 %include "ie86.inc" ; IntuitionEngine hardware definitions ; ============================================================================ ; CONSTANTS ; ============================================================================ ; --- Character Rendering --- ; Each character in our 8x8 font is 8 pixels tall. CHAR_HEIGHT equ 8 ; --- Scrolltext Horizontal Positions --- ; The two scrolltexts are positioned just left and right of screen centre. ; ANTIC/GTIA display is 320 pixels wide, so centre is 160. ; Players are positioned using HPOSP registers (0-255 range maps to screen). SCROLL1_X_BASE equ 152 ; Left scrolltext base X (cyan) SCROLL2_X_BASE equ 184 ; Right scrolltext base X (yellow) ; --- GTIA Colour Format --- ; GTIA colours are encoded as: HHHHLLLL ; HHHH = Hue (0-15): 0=grey, 1=gold, 2=orange, ... 9=cyan, etc. ; LLLL = Luminance (0-14 even numbers): 0=black, 14=white SCROLL1_COLOR equ 0x96 ; Dark cyan for left scrolltext SCROLL2_COLOR equ 0x16 ; Dark yellow/orange for right scrolltext ; --- Fixed-Point Arithmetic (16.16 Format) --- ; For smooth scrolling, we use fixed-point maths where: ; Upper 16 bits = integer part (pixel position) ; Lower 16 bits = fractional part (sub-pixel precision) ; scroll_y += 0x18000 means moving 1.5 pixels per frame. SCROLL_SPEED equ 0x18000 ; Vertical scroll speed (16.16 fixed) ; ============================================================================ ; CODE SECTION ; ============================================================================ section .text global _start ; ============================================================================ ; ENTRY POINT ; ============================================================================ ; The CPU begins execution here. We initialise all hardware subsystems ; before entering the main loop. ; ============================================================================ _start: ; --- Initialise Stack Pointer --- ; x86 uses a descending stack (grows toward lower addresses). ; ESP must point to valid RAM before any PUSH/CALL instructions. mov esp, STACK_TOP ; --- Disable Default VideoChip Layer --- ; This demo renders exclusively through ANTIC/GTIA. Leaving the ; default VideoChip enabled forces the compositor to include its ; unused scanline-aware layer, which can make ANTIC VBlank polling ; miss frames and visibly slow the plasma animation. mov byte [VIDEO_CTRL], 0 ; ============================================================================ ; ANTIC DISPLAY LIST SETUP ; ============================================================================ ; The display list is ANTIC's program - a sequence of instructions that ; control what appears on each scanline. This is conceptually similar to ; the Amiga's copper coprocessor, but with a different instruction set. ; ; ANTIC reads the display list from memory during each frame, executing ; instructions to generate the display. The CPU can modify the display ; list between frames to create animation effects. ; ============================================================================ ; --- Point ANTIC to Our Display List --- ; DLISTL/DLISTH form a 16-bit pointer to the display list. ; ANTIC reads instructions from this address during each frame. mov eax, display_list ; Get address of our display list mov byte [ANTIC_DLISTL], al ; Low byte of address shr eax, 8 ; Shift to get high byte mov byte [ANTIC_DLISTH], al ; High byte of address ; --- Enable ANTIC DMA --- ; DMACTL controls what ANTIC fetches from memory: ; ANTIC_DMA_DL = Enable display list DMA (required) ; ANTIC_DMA_NORMAL = Normal playfield width (40 bytes/line) ; ANTIC_DMA_PLAYER = Enable player/missile DMA ; Without DMA enabled, ANTIC outputs nothing. mov byte [ANTIC_DMACTL], ANTIC_DMA_DL | ANTIC_DMA_NORMAL | ANTIC_DMA_PLAYER ; --- Enable ANTIC Video Output --- ; IntuitionEngine extension - turns on ANTIC rendering. mov byte [ANTIC_ENABLE], ANTIC_ENABLE_VIDEO ; ============================================================================ ; GTIA PLAYER/MISSILE SETUP ; ============================================================================ ; GTIA provides 4 "players" (8-pixel wide sprites) that we use for scrolltext. ; Each player has: ; HPOSP: Horizontal position (0-255) ; GRAFP: Graphics data (8 bits = 8 pixels per scanline) ; COLPM: Colour register ; SIZEP: Width (0=normal, 1=double, 3=quad) ; ; We use players 0-1 for the left (cyan) scrolltext and ; players 2-3 for the right (yellow) scrolltext. ; ============================================================================ ; --- Enable Player Graphics --- ; GRACTL must have the PLAYER bit set to display players. mov byte [GTIA_GRACTL], GTIA_GRACTL_PLAYER ; --- Set Player Colours --- ; Each player has its own colour register. We use two colours: ; cyan (0x96) for left column, yellow (0x16) for right column. mov byte [GTIA_COLPM0], SCROLL1_COLOR mov byte [GTIA_COLPM1], SCROLL1_COLOR mov byte [GTIA_COLPM2], SCROLL2_COLOR mov byte [GTIA_COLPM3], SCROLL2_COLOR ; --- Set Player Widths --- ; SIZEP values: 0=normal (8 pixels), 1=double (16 pixels), 3=quad ; Double width makes the text more readable on the plasma background. mov byte [GTIA_SIZEP0], 1 mov byte [GTIA_SIZEP1], 1 mov byte [GTIA_SIZEP2], 1 mov byte [GTIA_SIZEP3], 1 ; ============================================================================ ; SID MUSIC PLAYBACK SETUP ; ============================================================================ ; The SID (Sound Interface Device) was the audio chip in the Commodore 64. ; The IntuitionEngine emulates it, allowing playback of .SID music files. ; Once started, the SID engine plays autonomously - no CPU intervention needed. ; ; Playing "OdDnB" by Jammer (Kamil Wolnikowski), a SID tune that ; demonstrates the chip's distinctive sound capabilities. ; ============================================================================ mov dword [SID_PLAY_PTR], sid_data mov dword [SID_PLAY_LEN], sid_data_end - sid_data mov dword [SID_PLAY_CTRL], 5 ; Start playback (looped) ; ============================================================================ ; INITIALISE ANIMATION STATE ; ============================================================================ ; Two time counters advance at different rates to create complex, ; non-repeating plasma patterns. Using relatively prime increments (2 and 3) ; ensures the pattern does not repeat for a very long time. ; ============================================================================ xor esi, esi ; Time counter 1 = 0 (increments by 2) xor edi, edi ; Time counter 2 = 0 (increments by 3) mov dword [scroll_y], 0 ; Vertical scroll position = 0 mov dword [base_char_idx], 0 ; ============================================================================ ; MAIN LOOP ; ============================================================================ ; Runs once per frame (~60 times per second). Each iteration: ; 1. Waits for vertical blank (top of frame) ; 2. Updates animation time counters ; 3. Waits for active display to begin ; 4. Renders each scanline with plasma colours and scrolltext ; ============================================================================ main_loop: ; --- Wait for Vertical Blank --- ; VBlank occurs when the beam returns from the bottom of the screen to ; the top. This is the safest time to update graphics state because ; nothing is being displayed. ; ; ANTIC_STATUS bit 0 = 1 during VBlank, 0 during active display. .wait_not_vb: test byte [ANTIC_STATUS], ANTIC_STATUS_VBLANK jnz .wait_not_vb .wait_vblank: test byte [ANTIC_STATUS], ANTIC_STATUS_VBLANK jz .wait_vblank ; --- Update Animation Time Counters --- ; Different increment rates create phase differences between effects. add esi, 2 ; Time1 advances slowly add edi, 3 ; Advance the second phase at a distinct rate. ; --- Update Vertical Scroll Position --- ; scroll_y is in 16.16 fixed-point format: ; Upper 16 bits = pixel offset ; Lower 16 bits = sub-pixel fraction mov eax, [scroll_y] add eax, SCROLL_SPEED ; Add ~1.5 pixels per frame mov [scroll_y], eax ; ===================================================================== ; PRE-CALCULATE SCROLL VALUES DURING VBLANK ; ===================================================================== ; Instead of doing expensive division (DIV) 192 times per frame in ; the scanline loop, we calculate the base character index ONCE here. ; ; ===================================================================== ; Get integer part of scroll position shr eax, 16 ; Integer part (pixel offset) mov [scroll_pixel], eax ; Calculate base_char_idx = (scroll_pixel / 8) % message_len shr eax, 3 ; Divide by 8 (char height) xor edx, edx mov ebx, message_len div ebx ; Slow DIV, but only ONCE per frame mov [base_char_idx], edx ; Store remainder (wrapped index) ; --- Wait for Active Display --- ; Synchronise with the start of the visible area so our per-scanline ; effects align correctly with the ANTIC display list. .wait_active: test byte [ANTIC_STATUS], ANTIC_STATUS_VBLANK jnz .wait_active ; --- Begin Scanline Rendering --- xor ecx, ecx ; ECX = scanline counter (0-191) ; ============================================================================ ; PER-SCANLINE RENDERING LOOP ; ============================================================================ ; Executes 192 times per frame, once for each visible scanline. On each: ; 1. Calculate and set the plasma background colour ; 2. Determine which scrolltext characters are visible ; 3. Set player graphics and positions for the scrolltext ; 4. WSYNC to synchronise with the next scanline ; ; WSYNC is crucial: writing to ANTIC_WSYNC halts the CPU until the next ; horizontal blank, ensuring our register changes take effect at the ; correct scanline. ; ============================================================================ .scanline_loop: ; ============================================================================ ; PLASMA BACKGROUND CALCULATION ; ============================================================================ ; The plasma effect combines multiple sine waves at different frequencies ; to create a smoothly animated colour pattern. We use 4 waves: ; ; Waves 1-2: Control the HUE (colour) component ; Waves 3-4: Control the LUMINANCE (brightness) component ; ; Each wave: sin_table[(scanline * freq + time) & 0xFF] ; The lookup table returns 0-255, representing a full sine cycle. ; ; Different frequencies and time offsets for each wave create complex ; interference patterns that appear to flow and shift organically. ; ============================================================================ ; === Wave 1: Fast Vertical Frequency (Hue) === ; Changes rapidly with scanline position, creating tight horizontal ; colour bands. mov eax, ecx shl eax, 3 ; Multiply by 8 (high frequency) add eax, esi ; Add time offset (animates the wave) and eax, 0xFF ; Wrap to 0-255 (sine table size) movzx eax, byte [sin_table + eax] mov ebx, eax ; EBX accumulates hue component ; === Wave 2: Medium Frequency with Time Offset (Hue) === ; A slower wave that creates broader colour regions. mov eax, ecx lea eax, [eax + eax*2] ; EAX = scanline * 3 add eax, edi ; Add time2 (different phase from wave 1) shl eax, 1 ; Double for more variation and eax, 0xFF movzx eax, byte [sin_table + eax] add ebx, eax ; Add to hue accumulator ; === Wave 3: Slow Undulation (Luminance) === ; Uses both time counters for complex motion. mov eax, ecx add eax, esi ; Add time1 add eax, edi ; Add time2 (creates beating pattern) and eax, 0xFF movzx eax, byte [sin_table + eax] mov ebp, eax ; EBP accumulates luminance component ; === Wave 4: Cross-Pattern (Luminance) === ; Subtracting time creates motion in the opposite direction, ; producing a "crossing" effect in the plasma pattern. mov eax, ecx imul eax, 5 ; Higher frequency multiplier add eax, esi sub eax, edi ; SUBTRACT time2 (opposite motion) and eax, 0xFF movzx eax, byte [sin_table + eax] add ebp, eax ; Add to luminance accumulator ; === Combine into GTIA Colour Format === ; GTIA colour byte: HHHHLLLL (hue in bits 4-7, luminance in bits 1-3) shr ebx, 1 ; Scale hue (0-510 -> 0-255) and ebx, 0xF0 ; Keep only upper nibble (hue) shr ebp, 5 ; Scale luminance (0-510 -> 0-15) and ebp, 0x0E ; Keep bits 1-3 (even values only) or ebx, ebp ; Combine hue and luminance mov byte [GTIA_COLBK], bl ; Set background colour for this scanline ; ============================================================================ ; VERTICAL SCROLLTEXT RENDERING ; ============================================================================ ; Two scrolltexts using the 4 available players: ; Players 0-1: Left scrolltext (cyan), different message portions ; Players 2-3: Right scrolltext (yellow), different message portions ; ; Each player displays one character at a time. By updating GRAFP (graphics) ; and HPOSP (position) for each scanline, we create the vertical scrolling ; and horizontal sine-wave wobble effect. ; ; For each scanline: ; 1. Determine which character is visible (based on scroll_y) ; 2. Determine which row of that character to display (0-7) ; 3. Look up the font data for that character row ; 4. Calculate X position with sine wobble ; 5. Write to GRAFP and HPOSP registers ; ============================================================================ ; --- Clear All Player Graphics --- ; Start with blank players; we set graphics only where characters appear mov byte [GTIA_GRAFP0], 0 mov byte [GTIA_GRAFP1], 0 mov byte [GTIA_GRAFP2], 0 mov byte [GTIA_GRAFP3], 0 ; ===================================================================== ; CHARACTER POSITION CALCULATION (OPTIMISED) ; ===================================================================== ; We pre-calculated base_char_idx during VBlank. Now we just add the ; scanline offset. Simple comparison/subtraction replaces DIV for the ; modulo wrapping, since we add at most 24 chars (192 scanlines / 8). ; ===================================================================== ; Calculate char_line = (scroll_pixel + scanline) & 7 mov eax, [scroll_pixel] add eax, ecx ; Add current scanline mov edx, eax and edx, 7 ; EDX = character row (0-7) ; Calculate char_index = base_char_idx + (scanline >> 3) mov eax, ecx shr eax, 3 ; scanline / 8 add eax, [base_char_idx] ; Simple modulo wrap (no DIV needed) cmp eax, message_len jl .no_wrap sub eax, message_len .no_wrap: ; Store for reuse across all four player calculations mov [cur_char_idx], eax mov [cur_char_line], edx ; -------------------------------------------------------------------------- ; SCROLLTEXT 1, CHARACTER 1 (Player 0 - Cyan, Left Column) ; -------------------------------------------------------------------------- ; --- Get ASCII Character from Message --- movzx ebx, byte [scroll_message + eax] sub ebx, 32 ; Convert ASCII to font index (space=0) jl .skip_char1 cmp ebx, 64 ; Font covers ASCII 32-95 (64 chars) jge .skip_char1 ; --- Look Up Font Data --- ; Font is 8 bytes per character: byte[char * 8 + row] shl ebx, 3 add ebx, edx movzx eax, byte [font_data + ebx] mov byte [GTIA_GRAFP0], al ; --- Calculate X Position with Sine Wobble --- ; X = base_x + sin(scanline + time) / 16 mov eax, ecx add eax, esi ; Add time for animation and eax, 0xFF movzx eax, byte [sin_table + eax] sub eax, 128 ; Centre around 0 (-128 to +127) sar eax, 4 ; Reduce amplitude (divide by 16) add eax, SCROLL1_X_BASE mov byte [GTIA_HPOSP0], al .skip_char1: ; -------------------------------------------------------------------------- ; SCROLLTEXT 1, CHARACTER 2 (Player 1 - Cyan, Left Column) ; -------------------------------------------------------------------------- ; Shows a different part of the message (offset by half the message length) mov eax, [cur_char_idx] mov edx, [cur_char_line] add eax, message_len/2 cmp eax, message_len jl .char1b_ok sub eax, message_len .char1b_ok: movzx ebx, byte [scroll_message + eax] sub ebx, 32 jl .skip_char1b cmp ebx, 64 jge .skip_char1b shl ebx, 3 add ebx, edx movzx eax, byte [font_data + ebx] mov byte [GTIA_GRAFP1], al ; X position with OPPOSITE phase wobble (add 128 to sine input) mov eax, ecx add eax, esi add eax, 128 ; Phase offset (half cycle) and eax, 0xFF movzx eax, byte [sin_table + eax] sub eax, 128 sar eax, 4 add eax, SCROLL1_X_BASE add eax, 20 ; Horizontal offset from first char mov byte [GTIA_HPOSP1], al .skip_char1b: ; -------------------------------------------------------------------------- ; SCROLLTEXT 2, CHARACTER 1 (Player 2 - Yellow, Right Column) ; -------------------------------------------------------------------------- mov eax, [cur_char_idx] mov edx, [cur_char_line] add eax, message_len/4 ; Different offset than scrolltext 1 cmp eax, message_len jl .char2_ok sub eax, message_len .char2_ok: movzx ebx, byte [scroll_message + eax] sub ebx, 32 jl .skip_char2 cmp ebx, 64 jge .skip_char2 shl ebx, 3 add ebx, edx movzx eax, byte [font_data + ebx] mov byte [GTIA_GRAFP2], al ; Use time2 (EDI) for different animation phase mov eax, ecx add eax, edi and eax, 0xFF movzx eax, byte [sin_table + eax] sub eax, 128 sar eax, 4 add eax, SCROLL2_X_BASE mov byte [GTIA_HPOSP2], al .skip_char2: ; -------------------------------------------------------------------------- ; SCROLLTEXT 2, CHARACTER 2 (Player 3 - Yellow, Right Column) ; -------------------------------------------------------------------------- mov eax, [cur_char_idx] mov edx, [cur_char_line] add eax, message_len/4 + message_len/2 ; Combined offset cmp eax, message_len jl .char2b_ok2 sub eax, message_len .char2b_ok2: movzx ebx, byte [scroll_message + eax] sub ebx, 32 jl .no_scroll_char cmp ebx, 64 jge .no_scroll_char shl ebx, 3 add ebx, edx movzx eax, byte [font_data + ebx] mov byte [GTIA_GRAFP3], al mov eax, ecx add eax, edi add eax, 128 ; Opposite phase and eax, 0xFF movzx eax, byte [sin_table + eax] sub eax, 128 sar eax, 4 add eax, SCROLL2_X_BASE add eax, 20 mov byte [GTIA_HPOSP3], al .no_scroll_char: ; --- WSYNC: Wait for Horizontal Sync --- ; Writing ANY value to ANTIC_WSYNC halts the CPU until the next ; horizontal blank period. This ensures our colour/graphics changes ; take effect at the correct scanline. ; ; On the real Atari, WSYNC was used extensively for colour cycling ; effects, player multiplexing, and precise DLI timing. mov byte [ANTIC_WSYNC], 0 ; --- Advance to Next Scanline --- inc ecx cmp ecx, 192 ; 192 visible scanlines jl .scanline_loop ; --- Loop Back for Next Frame --- jmp main_loop ; ============================================================================ ; DATA SECTION ; ============================================================================ section .data align 4 ; ============================================================================ ; ANTIC DISPLAY LIST ; ============================================================================ ; The display list is ANTIC's "program" - a sequence of instructions that ; control video output. Each instruction specifies what to render on one ; or more scanlines. ; ; INSTRUCTION FORMAT: ; Bits 0-3: Mode (graphics mode 0-15, or special instruction) ; Bit 4: HSCROL enable (horizontal fine scroll) ; Bit 5: VSCROL enable (vertical fine scroll) ; Bit 6: LMS (Load Memory Scan - next 2 bytes are screen address) ; Bit 7: DLI (trigger Display List Interrupt at end of this line) ; ; === BLANK LINES INSTEAD OF GRAPHICS MODE LINES === ; For plasma/raster bar effects where we only change COLBK (background ; colour), we do not need actual graphics mode lines. Mode 15 would require ; ANTIC to DMA 40 bytes per line from screen memory - that is 40 x 192 ; ; Using DL_BLANK1 instructions generates 1 blank line each with NO screen ; memory DMA. The CPU still changes COLBK via WSYNC. This reduces ANTIC's ; workload significantly and eliminates timing conflicts between ANTIC DMA ; and CPU memory accesses. ; ============================================================================ display_list: ; === Top Border: 24 blank scanlines === db DL_BLANK8 ; 8 blank lines (scanlines 0-7) db DL_BLANK8 ; 8 blank lines (scanlines 8-15) db DL_BLANK8 ; 8 blank lines (scanlines 16-23) ; === Main Display Area: 192 blank scanlines === ; Each DL_BLANK1 generates exactly 1 line with no DMA overhead. ; The CPU changes COLBK per-scanline via WSYNC. %rep 192 db DL_BLANK1 %endrep ; === Bottom Border: 24 blank scanlines === db DL_BLANK8 db DL_BLANK8 db DL_BLANK8 ; === Jump and Wait for Vertical Blank === ; DL_JVB tells ANTIC to wait for the next VBlank, then restart ; the display list from the specified address. This creates an ; infinite loop that repeats every frame. db DL_JVB dw display_list ; ---------------------------------------------------------------------------- ; Scroll State Variables ; ---------------------------------------------------------------------------- ; Scroll position (16.16 fixed-point) ; Upper 16 bits = pixel position, lower 16 bits = sub-pixel fraction scroll_y: dd 0 ; Pre-calculated values (computed once per frame during VBlank to avoid ; expensive DIV instructions in the per-scanline loop) scroll_pixel: dd 0 ; Integer part of scroll_y base_char_idx: dd 0 ; (scroll_pixel / 8) % message_len cur_char_idx: dd 0 ; Current character index (per scanline) cur_char_line: dd 0 ; Current row within character (0-7) ; ============================================================================ ; SCROLL MESSAGE ; ============================================================================ ; The text that scrolls vertically through the display. ; Leading/trailing spaces create pauses between repetitions. ; ============================================================================ scroll_message: db " INTUITION ENGINE 386 ASM WITH ATARI ANTIC/GTIA PLASMA BARS AND VERTICAL HARDWARE SINUS SCROLL AND SID MUSIC CODE BY INTUITION ODDNB MUSIC BY JAMMER GREETS TO ALL DEMOSCENERS VISIT INTUITIONSUBSYNTH.COM " message_len: equ $ - scroll_message ; ============================================================================ ; SINE TABLE ; ============================================================================ ; Pre-calculated sine wave values for one complete cycle (0-255 input). ; Output range: 0-255 (centred at 128) ; ; Formula: sin_table[i] = 128 + 127 * sin(2 * PI * i / 256) ; ; === A LOOKUP TABLE === ; On 8-bit systems, calculating sine in real-time was impossible. Even on ; table gives ~1.4 degree resolution - plenty for smooth animation. ; ; Usage: value = sin_table[(angle + offset) & 0xFF] ; Where angle is 0-255 representing 0-360 degrees. ; ============================================================================ sin_table: ; Quadrant 1: 0 to 90 degrees (indices 0-63) - rising from 128 to 255 db 128, 131, 134, 137, 140, 143, 146, 149 db 152, 155, 158, 162, 165, 167, 170, 173 db 176, 179, 182, 185, 188, 190, 193, 196 db 198, 201, 203, 206, 208, 211, 213, 215 db 218, 220, 222, 224, 226, 228, 230, 232 db 234, 235, 237, 238, 240, 241, 243, 244 db 245, 246, 248, 249, 250, 250, 251, 252 db 253, 253, 254, 254, 254, 255, 255, 255 ; Quadrant 2: 90 to 180 degrees (indices 64-127) - falling from 255 to 128 db 255, 255, 255, 255, 254, 254, 254, 253 db 253, 252, 251, 250, 250, 249, 248, 246 db 245, 244, 243, 241, 240, 238, 237, 235 db 234, 232, 230, 228, 226, 224, 222, 220 db 218, 215, 213, 211, 208, 206, 203, 201 db 198, 196, 193, 190, 188, 185, 182, 179 db 176, 173, 170, 167, 165, 162, 158, 155 db 152, 149, 146, 143, 140, 137, 134, 131 ; Quadrant 3: 180 to 270 degrees (indices 128-191) - falling from 128 to 0 db 128, 124, 121, 118, 115, 112, 109, 106 db 103, 100, 97, 93, 90, 88, 85, 82 db 79, 76, 73, 70, 67, 65, 62, 59 db 57, 54, 52, 49, 47, 44, 42, 40 db 37, 35, 33, 31, 29, 27, 25, 23 db 21, 20, 18, 17, 15, 14, 12, 11 db 10, 9, 7, 6, 5, 5, 4, 3 db 2, 2, 1, 1, 1, 0, 0, 0 ; Quadrant 4: 270 to 360 degrees (indices 192-255) - rising from 0 to 128 db 0, 0, 0, 0, 1, 1, 1, 2 db 2, 3, 4, 5, 5, 6, 7, 9 db 10, 11, 12, 14, 15, 17, 18, 20 db 21, 23, 25, 27, 29, 31, 33, 35 db 37, 40, 42, 44, 47, 49, 52, 54 db 57, 59, 62, 65, 67, 70, 73, 76 db 79, 82, 85, 88, 90, 93, 97, 100 db 103, 106, 109, 112, 115, 118, 121, 124 ; ============================================================================ ; 8x8 BITMAP FONT ; ============================================================================ ; Each character is 8 bytes (8 rows of 8 pixels). ; Bit 7 = leftmost pixel, bit 0 = rightmost pixel. ; 1 = foreground (player colour), 0 = transparent. ; ; Characters included: ASCII 32-95 (space through underscore) ; This covers uppercase letters, numbers, and common punctuation. ; ; Example: Letter 'A' (ASCII 65, font index 33) ; Row 0: 00111000 = 0x38 ( *** ) ; Row 1: 01101100 = 0x6C ( ** ** ) ; Row 2: 11000110 = 0xC6 ( ** ** ) ; Row 3: 11111110 = 0xFE ( ******* ) ; Row 4: 11000110 = 0xC6 ( ** ** ) ; Row 5: 11000110 = 0xC6 ( ** ** ) ; Row 6: 11000110 = 0xC6 ( ** ** ) ; Row 7: 00000000 = 0x00 ( ) ; ============================================================================ font_data: ; ASCII 32: Space db 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 ; ASCII 33: ! db 0x18, 0x18, 0x18, 0x18, 0x18, 0x00, 0x18, 0x00 ; ASCII 34: " db 0x6C, 0x6C, 0x24, 0x00, 0x00, 0x00, 0x00, 0x00 ; ASCII 35: # db 0x6C, 0x6C, 0xFE, 0x6C, 0xFE, 0x6C, 0x6C, 0x00 ; ASCII 36: $ db 0x18, 0x7E, 0xC0, 0x7C, 0x06, 0xFC, 0x18, 0x00 ; ASCII 37: % db 0x00, 0xC6, 0xCC, 0x18, 0x30, 0x66, 0xC6, 0x00 ; ASCII 38: & db 0x38, 0x6C, 0x38, 0x76, 0xDC, 0xCC, 0x76, 0x00 ; ASCII 39: ' db 0x18, 0x18, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00 ; ASCII 40: ( db 0x0C, 0x18, 0x30, 0x30, 0x30, 0x18, 0x0C, 0x00 ; ASCII 41: ) db 0x30, 0x18, 0x0C, 0x0C, 0x0C, 0x18, 0x30, 0x00 ; ASCII 42: * db 0x00, 0x66, 0x3C, 0xFF, 0x3C, 0x66, 0x00, 0x00 ; ASCII 43: + db 0x00, 0x18, 0x18, 0x7E, 0x18, 0x18, 0x00, 0x00 ; ASCII 44: , db 0x00, 0x00, 0x00, 0x00, 0x00, 0x18, 0x18, 0x30 ; ASCII 45: - db 0x00, 0x00, 0x00, 0x7E, 0x00, 0x00, 0x00, 0x00 ; ASCII 46: . db 0x00, 0x00, 0x00, 0x00, 0x00, 0x18, 0x18, 0x00 ; ASCII 47: / db 0x06, 0x0C, 0x18, 0x30, 0x60, 0xC0, 0x80, 0x00 ; ASCII 48-57: Digits 0-9 db 0x7C, 0xC6, 0xCE, 0xD6, 0xE6, 0xC6, 0x7C, 0x00 ; 0 db 0x18, 0x38, 0x18, 0x18, 0x18, 0x18, 0x7E, 0x00 ; 1 db 0x7C, 0xC6, 0x06, 0x1C, 0x30, 0x66, 0xFE, 0x00 ; 2 db 0x7C, 0xC6, 0x06, 0x3C, 0x06, 0xC6, 0x7C, 0x00 ; 3 db 0x1C, 0x3C, 0x6C, 0xCC, 0xFE, 0x0C, 0x1E, 0x00 ; 4 db 0xFE, 0xC0, 0xC0, 0xFC, 0x06, 0xC6, 0x7C, 0x00 ; 5 db 0x38, 0x60, 0xC0, 0xFC, 0xC6, 0xC6, 0x7C, 0x00 ; 6 db 0xFE, 0xC6, 0x0C, 0x18, 0x30, 0x30, 0x30, 0x00 ; 7 db 0x7C, 0xC6, 0xC6, 0x7C, 0xC6, 0xC6, 0x7C, 0x00 ; 8 db 0x7C, 0xC6, 0xC6, 0x7E, 0x06, 0x0C, 0x78, 0x00 ; 9 ; ASCII 58: : db 0x00, 0x18, 0x18, 0x00, 0x00, 0x18, 0x18, 0x00 ; ASCII 59: ; db 0x00, 0x18, 0x18, 0x00, 0x00, 0x18, 0x18, 0x30 ; ASCII 60: < db 0x0C, 0x18, 0x30, 0x60, 0x30, 0x18, 0x0C, 0x00 ; ASCII 61: = db 0x00, 0x00, 0x7E, 0x00, 0x00, 0x7E, 0x00, 0x00 ; ASCII 62: > db 0x60, 0x30, 0x18, 0x0C, 0x18, 0x30, 0x60, 0x00 ; ASCII 63: ? db 0x7C, 0xC6, 0x0C, 0x18, 0x18, 0x00, 0x18, 0x00 ; ASCII 64: @ db 0x7C, 0xC6, 0xDE, 0xDE, 0xDE, 0xC0, 0x78, 0x00 ; ASCII 65-90: Uppercase letters A-Z db 0x38, 0x6C, 0xC6, 0xFE, 0xC6, 0xC6, 0xC6, 0x00 ; A db 0xFC, 0x66, 0x66, 0x7C, 0x66, 0x66, 0xFC, 0x00 ; B db 0x3C, 0x66, 0xC0, 0xC0, 0xC0, 0x66, 0x3C, 0x00 ; C db 0xF8, 0x6C, 0x66, 0x66, 0x66, 0x6C, 0xF8, 0x00 ; D db 0xFE, 0x62, 0x68, 0x78, 0x68, 0x62, 0xFE, 0x00 ; E db 0xFE, 0x62, 0x68, 0x78, 0x68, 0x60, 0xF0, 0x00 ; F db 0x3C, 0x66, 0xC0, 0xC0, 0xCE, 0x66, 0x3A, 0x00 ; G db 0xC6, 0xC6, 0xC6, 0xFE, 0xC6, 0xC6, 0xC6, 0x00 ; H db 0x3C, 0x18, 0x18, 0x18, 0x18, 0x18, 0x3C, 0x00 ; I db 0x1E, 0x0C, 0x0C, 0x0C, 0xCC, 0xCC, 0x78, 0x00 ; J db 0xE6, 0x66, 0x6C, 0x78, 0x6C, 0x66, 0xE6, 0x00 ; K db 0xF0, 0x60, 0x60, 0x60, 0x62, 0x66, 0xFE, 0x00 ; L db 0xC6, 0xEE, 0xFE, 0xFE, 0xD6, 0xC6, 0xC6, 0x00 ; M db 0xC6, 0xE6, 0xF6, 0xDE, 0xCE, 0xC6, 0xC6, 0x00 ; N db 0x7C, 0xC6, 0xC6, 0xC6, 0xC6, 0xC6, 0x7C, 0x00 ; O db 0xFC, 0x66, 0x66, 0x7C, 0x60, 0x60, 0xF0, 0x00 ; P db 0x7C, 0xC6, 0xC6, 0xC6, 0xD6, 0x7C, 0x0E, 0x00 ; Q db 0xFC, 0x66, 0x66, 0x7C, 0x6C, 0x66, 0xE6, 0x00 ; R db 0x7C, 0xC6, 0xE0, 0x78, 0x0E, 0xC6, 0x7C, 0x00 ; S db 0x7E, 0x7E, 0x5A, 0x18, 0x18, 0x18, 0x3C, 0x00 ; T db 0xC6, 0xC6, 0xC6, 0xC6, 0xC6, 0xC6, 0x7C, 0x00 ; U db 0xC6, 0xC6, 0xC6, 0xC6, 0x6C, 0x38, 0x10, 0x00 ; V db 0xC6, 0xC6, 0xD6, 0xFE, 0xFE, 0xEE, 0xC6, 0x00 ; W db 0xC6, 0xC6, 0x6C, 0x38, 0x6C, 0xC6, 0xC6, 0x00 ; X db 0x66, 0x66, 0x66, 0x3C, 0x18, 0x18, 0x3C, 0x00 ; Y db 0xFE, 0xC6, 0x8C, 0x18, 0x32, 0x66, 0xFE, 0x00 ; Z ; ASCII 91: [ db 0x3C, 0x30, 0x30, 0x30, 0x30, 0x30, 0x3C, 0x00 ; ASCII 92: backslash db 0xC0, 0x60, 0x30, 0x18, 0x0C, 0x06, 0x02, 0x00 ; ASCII 93: ] db 0x3C, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x3C, 0x00 ; ASCII 94: ^ db 0x10, 0x38, 0x6C, 0xC6, 0x00, 0x00, 0x00, 0x00 ; ASCII 95: _ db 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF ; ============================================================================ ; SID MUSIC DATA ; ============================================================================ ; "OdDnB" by Jammer (Kamil Wolnikowski) - a SID tune demonstrating ; the Commodore 64's distinctive sound chip capabilities. ; ; The SID file format contains header metadata, load address, ; initialisation routines, and music data (patterns, instruments, ; sequences). The IntuitionEngine's SID player handles all the ; complexity; we just provide the file data and it plays automatically. ; ============================================================================ align 4 sid_data: incbin "../assets/music/OdDnB.sid" sid_data_end: