MC6847.js

/**
 * jsMC1000 - MC-1000 emulator in JavaScript.
 * Emerson Jose Silveira da Costa <emerson.costa@gmail.com>, alias "Ensjo".
 * http://ensjo.net/mc-1000/jsmc1000
 */

/**
 * MC6847 class.
 * 2011-11-09.
 * 
 * Emulation of Motorola MC6847 Video Display Generator.
 * 
 * ¬A/G ¬A/S ¬INT/EXT INV GM2 GM1 GM0 MODE
 *   0    0      0     0   X   X   X  Internal Alphanumerics
 *   0    0      0     1   X   X   X  Internal Alphanumerics Inverted
 *   0    0      1     0   X   X   X  External Alphanumerics
 *   0    0      1     1   X   X   X  External Alphanumerics Inverted
 *   0    1      0     X   X   X   X  Semigraphics 4 (SG4)
 *   0    1      1     X   X   X   X  Semigraphics 6 (SG6)
 *   1    X      X     X   0   0   0  64x64 Color Graphics One (CG1)
 *   1    X      X     X   0   0   1  128X64 Resolution Graphics One (RG1)
 *   1    X      X     X   0   1   0  128x64 Color Graphics Two (CG2)
 *   1    X      X     X   0   1   1  128x96 Resolution Graphics Two (RG2)
 *   1    X      X     X   1   0   0  128x96 Color Graphics Three (CG3)
 *   1    X      X     X   1   0   1  128x192 Resolution Graphics Three (RG3)
 *   1    X      X     X   1   1   0  128x192 Color Graphics Six (CG6)
 *   1    X      X     X   1   1   1  256x192 Resolution Graphics Six (RG6)
 * 
 * CSS specifies alternative palettes.
 */

function MC6847(delegate) {
	this.delegate = delegate;
	
	// Pins.
	this.da = 0; // DA0~DA12 (Display Address Output Lines).
	this.dd = 0; // DD0~DD7 (Data Input Lines).
	this.ag = 0; // ¬A/G (Alphanumerics/Graphics).
	this.as = 0; // ¬A/S (Alphanumerics/Semigraphics).
	this.intext = 0; // ¬INT/EXT (Internal/External).
	this.inv = 0; // INV (Invert).
	this.gm = 0; // GM0~GM2 (Graphic Mode).
	this.css = 0; // CSS (Color Select).
	
	this.ms = 1; // ¬MS (Memory Select).
	this.fs = 0; // FS (Field Sinc).
	this.rp = 1; // RP (Row Preset).
	
	this.lineCounter = 0;
	this.rowCounter = 0;
	
	this.borderColor = MC6847.COLOR.BLACK;
}

MC6847.FONT = [
	[0x00,0x00,0x00,0x1c,0x22,0x02,0x1a,0x2a,0x2a,0x1c,0x00,0x00], // @
	[0x00,0x00,0x00,0x08,0x14,0x22,0x22,0x3e,0x22,0x22,0x00,0x00], // A
	[0x00,0x00,0x00,0x3c,0x12,0x12,0x1c,0x12,0x12,0x3c,0x00,0x00], // B
	[0x00,0x00,0x00,0x1c,0x22,0x20,0x20,0x20,0x22,0x1c,0x00,0x00], // C
	[0x00,0x00,0x00,0x3c,0x12,0x12,0x12,0x12,0x12,0x3c,0x00,0x00], // D
	[0x00,0x00,0x00,0x3e,0x20,0x20,0x3c,0x20,0x20,0x3e,0x00,0x00], // E
	[0x00,0x00,0x00,0x3e,0x20,0x20,0x3c,0x20,0x20,0x20,0x00,0x00], // F
	[0x00,0x00,0x00,0x1e,0x20,0x20,0x26,0x22,0x22,0x1e,0x00,0x00], // G
	[0x00,0x00,0x00,0x22,0x22,0x22,0x3e,0x22,0x22,0x22,0x00,0x00], // H
	[0x00,0x00,0x00,0x1c,0x08,0x08,0x08,0x08,0x08,0x1c,0x00,0x00], // I
	[0x00,0x00,0x00,0x02,0x02,0x02,0x02,0x02,0x22,0x1c,0x00,0x00], // J
	[0x00,0x00,0x00,0x22,0x24,0x28,0x30,0x28,0x24,0x22,0x00,0x00], // K
	[0x00,0x00,0x00,0x20,0x20,0x20,0x20,0x20,0x20,0x3e,0x00,0x00], // L
	[0x00,0x00,0x00,0x22,0x36,0x2a,0x2a,0x22,0x22,0x22,0x00,0x00], // M
	[0x00,0x00,0x00,0x22,0x32,0x2a,0x26,0x22,0x22,0x22,0x00,0x00], // N
	[0x00,0x00,0x00,0x3e,0x22,0x22,0x22,0x22,0x22,0x3e,0x00,0x00], // O
	[0x00,0x00,0x00,0x3c,0x22,0x22,0x3c,0x20,0x20,0x20,0x00,0x00], // P
	[0x00,0x00,0x00,0x1c,0x22,0x22,0x22,0x2a,0x24,0x18,0x00,0x00], // Q
	[0x00,0x00,0x00,0x3c,0x22,0x22,0x3c,0x28,0x24,0x22,0x00,0x00], // R
	[0x00,0x00,0x00,0x1c,0x22,0x10,0x08,0x04,0x22,0x1c,0x00,0x00], // S
	[0x00,0x00,0x00,0x3e,0x08,0x08,0x08,0x08,0x08,0x08,0x00,0x00], // T
	[0x00,0x00,0x00,0x22,0x22,0x22,0x22,0x22,0x22,0x1c,0x00,0x00], // U
	[0x00,0x00,0x00,0x22,0x22,0x22,0x14,0x14,0x08,0x08,0x00,0x00], // V
	[0x00,0x00,0x00,0x22,0x22,0x22,0x2a,0x2a,0x36,0x22,0x00,0x00], // W
	[0x00,0x00,0x00,0x22,0x22,0x14,0x08,0x14,0x22,0x22,0x00,0x00], // X
	[0x00,0x00,0x00,0x22,0x22,0x14,0x08,0x08,0x08,0x08,0x00,0x00], // Y
	[0x00,0x00,0x00,0x3e,0x02,0x04,0x08,0x10,0x20,0x3e,0x00,0x00], // Z
	[0x00,0x00,0x00,0x38,0x20,0x20,0x20,0x20,0x20,0x38,0x00,0x00], // [
	[0x00,0x00,0x00,0x20,0x20,0x10,0x08,0x04,0x02,0x02,0x00,0x00], // \
	[0x00,0x00,0x00,0x0e,0x02,0x02,0x02,0x02,0x02,0x0e,0x00,0x00], // ]
	[0x00,0x00,0x00,0x08,0x1c,0x2a,0x08,0x08,0x08,0x08,0x00,0x00], // (up arrow)
	[0x00,0x00,0x00,0x00,0x08,0x10,0x3e,0x10,0x08,0x00,0x00,0x00], // (left arrow)
	[0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00], // (space)
	[0x00,0x00,0x00,0x08,0x08,0x08,0x08,0x08,0x00,0x08,0x00,0x00], // !
	[0x00,0x00,0x00,0x14,0x14,0x00,0x00,0x00,0x00,0x00,0x00,0x00], // "
	[0x00,0x00,0x00,0x14,0x14,0x36,0x00,0x36,0x14,0x14,0x00,0x00], // #
	[0x00,0x00,0x00,0x08,0x1e,0x20,0x1c,0x02,0x3c,0x08,0x00,0x00], // $
	[0x00,0x00,0x00,0x32,0x32,0x04,0x08,0x10,0x26,0x26,0x00,0x00], // %
	[0x00,0x00,0x00,0x10,0x28,0x28,0x10,0x2a,0x24,0x1a,0x00,0x00], // &
	[0x00,0x00,0x00,0x18,0x18,0x18,0x00,0x00,0x00,0x00,0x00,0x00], // '
	[0x00,0x00,0x00,0x08,0x10,0x20,0x20,0x20,0x10,0x08,0x00,0x00], // (
	[0x00,0x00,0x00,0x08,0x04,0x02,0x02,0x02,0x04,0x08,0x00,0x00], // )
	[0x00,0x00,0x00,0x00,0x08,0x1c,0x3e,0x1c,0x08,0x00,0x00,0x00], // *
	[0x00,0x00,0x00,0x00,0x08,0x08,0x3e,0x08,0x08,0x00,0x00,0x00], // +
	[0x00,0x00,0x00,0x00,0x00,0x00,0x30,0x30,0x10,0x20,0x00,0x00], // ,
	[0x00,0x00,0x00,0x00,0x00,0x00,0x3e,0x00,0x00,0x00,0x00,0x00], // -
	[0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x30,0x30,0x00,0x00], // .
	[0x00,0x00,0x00,0x02,0x02,0x04,0x08,0x10,0x20,0x20,0x00,0x00], // /
	[0x00,0x00,0x00,0x18,0x24,0x24,0x24,0x24,0x24,0x18,0x00,0x00], // 0
	[0x00,0x00,0x00,0x08,0x18,0x08,0x08,0x08,0x08,0x1c,0x00,0x00], // 1
	[0x00,0x00,0x00,0x1c,0x22,0x02,0x1c,0x20,0x20,0x3e,0x00,0x00], // 2
	[0x00,0x00,0x00,0x1c,0x22,0x02,0x1c,0x02,0x22,0x1c,0x00,0x00], // 3
	[0x00,0x00,0x00,0x04,0x0c,0x14,0x3e,0x04,0x04,0x04,0x00,0x00], // 4
	[0x00,0x00,0x00,0x3e,0x20,0x3c,0x02,0x02,0x22,0x1c,0x00,0x00], // 5
	[0x00,0x00,0x00,0x1c,0x20,0x20,0x3c,0x22,0x22,0x1c,0x00,0x00], // 6
	[0x00,0x00,0x00,0x3e,0x02,0x04,0x08,0x10,0x20,0x20,0x00,0x00], // 7
	[0x00,0x00,0x00,0x1c,0x22,0x22,0x1c,0x22,0x22,0x1c,0x00,0x00], // 8
	[0x00,0x00,0x00,0x1c,0x22,0x22,0x1e,0x02,0x02,0x1c,0x00,0x00], // 9
	[0x00,0x00,0x00,0x00,0x18,0x18,0x00,0x18,0x18,0x00,0x00,0x00], // :
	[0x00,0x00,0x00,0x18,0x18,0x00,0x18,0x18,0x08,0x10,0x00,0x00], // ;
	[0x00,0x00,0x00,0x04,0x08,0x10,0x20,0x10,0x08,0x04,0x00,0x00], // <
	[0x00,0x00,0x00,0x00,0x00,0x3e,0x00,0x3e,0x00,0x00,0x00,0x00], // =
	[0x00,0x00,0x00,0x10,0x08,0x04,0x02,0x04,0x08,0x10,0x00,0x00], // >
	[0x00,0x00,0x00,0x18,0x24,0x04,0x08,0x08,0x00,0x08,0x00,0x00], // ?
];

MC6847.COLOR = (function() {
	var colorDataArray = [
		//  R,   G,   B,   A.
		[0x07,0xff,0x00,0xff], // Green
		[0xff,0xff,0x00,0xff], // Yellow.
		[0x3b,0x08,0xff,0xff], // Blue.
		[0xcc,0x00,0x3b,0xff], // Red.
		[0xff,0xff,0xff,0xff], // Buff.
		[0x07,0xe3,0x99,0xff], // Cyan.
		[0xff,0x1c,0xff,0xff], // Magenta.
		[0xff,0x81,0x00,0xff], // Orange.
		[0x00,0x00,0x00,0xff], // Black.
		[0x00,0x7c,0x00,0xff], // Dark green.
		[0x91,0x00,0x00,0xff]  // Dark red.
	];
	var imageDataArray = [];
	
	for(var i in colorDataArray) {
		var id = new ImageData(1, 1); // 1 pixel.
		for (var j = 0; j < 4; j++) {
			id.data[j] = colorDataArray[i][j];
		}
		imageDataArray[i] = id;
	}
	
	return imageDataArray;
})();

MC6847.COLOR.GREEN      = MC6847.COLOR[0];
MC6847.COLOR.YELLOW     = MC6847.COLOR[1];
MC6847.COLOR.BLUE       = MC6847.COLOR[2];
MC6847.COLOR.RED        = MC6847.COLOR[3];
MC6847.COLOR.BUFF       = MC6847.COLOR[4];
MC6847.COLOR.CYAN       = MC6847.COLOR[5];
MC6847.COLOR.MAGENTA    = MC6847.COLOR[6];
MC6847.COLOR.ORANGE     = MC6847.COLOR[7];
MC6847.COLOR.BLACK      = MC6847.COLOR[8];
MC6847.COLOR.DARK_GREEN = MC6847.COLOR[9];
MC6847.COLOR.DARK_RED   = MC6847.COLOR[10];

MC6847.PALETTE = {
	RESOLUTION_GRAPHICS: [
		[
			MC6847.COLOR.DARK_GREEN,
			MC6847.COLOR.GREEN
		],
		[
			MC6847.COLOR.BLACK,
			MC6847.COLOR.BUFF
		]
	],
	
	COLOR_GRAPHICS: [
		[
			MC6847.COLOR.GREEN,
			MC6847.COLOR.YELLOW,
			MC6847.COLOR.BLUE,
			MC6847.COLOR.RED
		],
		[
			MC6847.COLOR.BUFF,
			MC6847.COLOR.CYAN,
			MC6847.COLOR.MAGENTA,
			MC6847.COLOR.ORANGE
		]
	],

	SEMIGRAPHICS: [
		MC6847.COLOR.GREEN,
		MC6847.COLOR.YELLOW,
		MC6847.COLOR.BLUE,
		MC6847.COLOR.RED,
		MC6847.COLOR.BUFF,
		MC6847.COLOR.CYAN,
		MC6847.COLOR.MAGENTA,
		MC6847.COLOR.ORANGE
	],

	ALPHANUMERICS: [
		[
			MC6847.COLOR.DARK_GREEN,
			MC6847.COLOR.GREEN
		],
		[
			MC6847.COLOR.DARK_RED,
			MC6847.COLOR.ORANGE
		]
	]
};

MC6847.VERTICAL_BORDER = 25;
MC6847.HORIZONTAL_BORDER = 32;

MC6847.SCREEN_WIDTH = MC6847.HORIZONTAL_BORDER + 256 + MC6847.HORIZONTAL_BORDER;
MC6847.SCREEN_HEIGHT = MC6847.VERTICAL_BORDER + 192 + MC6847.VERTICAL_BORDER;

MC6847.prototype.setup = function() {
	this.bytesPerLine = 32;
	this.bitsToParse = 8;
	if (this.ag) {
		// Graphic modes.
		this.pattern = this.dd;
		switch (this.gm) {
			case 0: // 64x64 Color Graphics One (CG1)
				this.palette = MC6847.PALETTE.COLOR_GRAPHICS[this.css ? 1 : 0];
				this.borderColor = this.palette[0];
				this.bytesPerLine = 16;
				this.bitsPerPixel = 2;
				this.pixelWidth = 4;
				this.elementHeight = 3;
				break;
			case 1: // 128x64 Resolution Graphics One (RG1)
			case 3: // 128x96 Resolution Graphics Two (RG2)
			case 5: // 128x192 Resolution Graphics Three (RG3)
				this.palette = MC6847.PALETTE.RESOLUTION_GRAPHICS[this.css ? 1 : 0];
				this.borderColor = this.palette[1];
				this.bytesPerLine = 16;
				this.bitsPerPixel = 1;
				this.pixelWidth = 2;
				this.elementHeight = 3 - (this.gm >> 1);
				break;
			case 2: // 128x64 Color Graphics Two (CG2)
			case 4: // 128x96 Color Graphics Three (CG3)
			case 6: // 128x192 Color Graphics Six (CG6) 
				this.palette = MC6847.PALETTE.COLOR_GRAPHICS[this.css ? 1 : 0];
				this.borderColor = this.palette[0];
				this.bitsPerPixel = 2;
				this.pixelWidth = 2;
				this.elementHeight = 4 - (this.gm >> 1);
				break;
			case 7: // 256x192 Resolution Graphics Six (RG6)
			default:
				this.palette = MC6847.PALETTE.RESOLUTION_GRAPHICS[this.css ? 1 : 0];
				this.borderColor = this.palette[1];
				this.bitsPerPixel = 1;
				this.pixelWidth = 1;
				this.elementHeight = 1;
				break;
		}
	} else {
		// Non-graphic modes.
		this.borderColor = MC6847.COLOR.BLACK;
		this.elementHeight = 12;
		if (this.as) {
			// Semigraphics.
			this.bitsToParse = 2;
			this.bitsPerPixel = 1;
			this.pixelWidth = 4;
			if (this.intext) {
				// Semigraphics 6.
				// Bits 0-5 define lighted (non-background) blocks; 6-7 define color within palette.
				// [5][4]
				// [3][2]
				// [1][0]
				if (this.rowCounter < 4) {
					this.pattern = (this.dd >> 4) & 0x03;
				} else if (this.rowCounter < 8) {
					this.pattern = (this.dd >> 2) & 0x03;
				} else {
					this.pattern = this.dd & 0x03;
				}
				this.palette = [
					MC6847.COLOR.BLACK,
					MC6847.PALETTE.COLOR_GRAPHICS[this.css][(this.dd >> 6) & 0x3]
				];
			} else {
				// Semigraphics 4.
				// Bits 0-3 define lighted (non-background) blocks; 4-6 define color.
				// [3][2]
				// [1][0]
				if (this.rowCounter < 6) {
					this.pattern = (this.dd >> 2) & 0x03;
				} else {
					this.pattern = this.dd & 0x03;
				}
				this.palette = [
					MC6847.COLOR.BLACK,
					MC6847.PALETTE.SEMIGRAPHICS[(this.dd >> 4) & 0x07]
				];
			}
		} else {
			// Alphanumerics.
			this.palette = MC6847.PALETTE.ALPHANUMERICS[this.css];
			this.bitsPerPixel = 1;
			this.pixelWidth = 1;
			if (this.intext) {
				// External.
				// Fetch pattern from data input lines.
				this.pattern = this.dd;
			} else {
				// Internal.
				// Fetch pattern from internal font data.
				// Data input lines select character to be displayed.
				this.pattern = MC6847.FONT[this.dd & 0x3f][this.rowCounter];
			}
			if (this.inv) {
				// Inverted.
				this.pattern = 0xff ^ this.pattern;
			}
		}
	}
};

MC6847.prototype.drawLine = function() {
	var ctx = this.delegate.mc6847GetCanvas().getContext("2d");
	
	// Draw upper border if first line.
	if (this.lineCounter == 0) {
		// Vertical blanking: 13 H lines.
		this.delegate.mc6847SetFs(this.fs = 1);
		// Upper border: 25 H lines.
		var imageData = new ImageData(MC6847.SCREEN_WIDTH, MC6847.VERTICAL_BORDER);
		var a = 0;
		for (var y = 0; y < MC6847.VERTICAL_BORDER; y++) {
			for (var x = 0; x < MC6847.SCREEN_WIDTH; x++) {
				for (var b = 0; b < 4; b++) {
					imageData.data[a++] = this.borderColor.data[b];
				}
			}
		}
		ctx.putImageData(imageData, 0, 0);
			
		// Active display area: 192 H lines.
		this.da = 0;
		this.rowCounter = 0;
	}
	
	var imageData = new ImageData(MC6847.SCREEN_WIDTH, 1);
	var a = 0;
	// Left border.
	for (var x = 0; x < MC6847.HORIZONTAL_BORDER; x++) {
		for (var b = 0; b < 4; b++) {
			imageData.data[a++] = this.borderColor.data[b];
		}
	}

	// Active display area.
	this.ag = this.delegate.mc6847GetAg();
	this.gm = this.delegate.mc6847GetGm();
	for (var xx = 0; xx < 256; ) {
		this.delegate.mc6847SetAddress(this.da);
		this.dd = this.delegate.mc6847GetData();
		this.as = this.delegate.mc6847GetAs();
		this.intext = this.delegate.mc6847GetIntext();
		this.inv = this.delegate.mc6847GetInv();
		this.css = this.delegate.mc6847GetCss();
		this.setup();
		var bitMask = ((1 << this.bitsPerPixel) - 1) << (this.bitsToParse - this.bitsPerPixel);
		for (var i = this.bitsToParse; i > 0; i -= this.bitsPerPixel) {
			var pixelColor = this.palette[(this.pattern & bitMask) >> (i - this.bitsPerPixel)];
			for (var p = 0; p < this.pixelWidth; p++) {
				for (var b = 0; b < 4; b++) {
					imageData.data[a++] = pixelColor.data[b];
				}
				x++;
				xx++;
			}
			bitMask >>= this.bitsPerPixel;
		}
		this.da =
			(this.da & (0x1fff ^ (this.bytesPerLine - 1))) |
			((this.da + 1) & (this.bytesPerLine -1));
	}
	if (++this.rowCounter >= this.elementHeight) {
		this.da += this.bytesPerLine;
		this.rowCounter = 0;
	}
	if (this.ag == 0) {
		this.delegate.mc6847SetRp(this.rp = 0);
		this.delegate.mc6847SetRp(this.rp = 1);
	}
	// Right border.
	for ( ; x < MC6847.SCREEN_WIDTH; x++) {
		for (var b = 0; b < 4; b++) {
			imageData.data[a++] = this.borderColor.data[b];
		}
	}
	ctx.putImageData(imageData, 0, MC6847.VERTICAL_BORDER + this.lineCounter);
	
	// Draw lower border if last line.
	if (this.lineCounter++ == 191) {
		this.delegate.mc6847SetFs(this.fs = 0);
		// Bottom border: 26 H lines.
		var imageData = new ImageData(MC6847.SCREEN_WIDTH, MC6847.VERTICAL_BORDER);
		var a = 0;
		for (y = 0; y < MC6847.VERTICAL_BORDER; y++) {
			for (x = 0; x < MC6847.SCREEN_WIDTH; x++) {
				for (var b = 0; b < 4; b++) {
					imageData.data[a++] = this.borderColor.data[b];
				}
			}
		}
		ctx.putImageData(imageData, 0, MC6847.VERTICAL_BORDER + 192);
		// Vertical retrace: 6 H lines.
		this.lineCounter = 0;
	}
};

MC6847.prototype.drawScreen = function() {
	do {
		this.drawLine()
	} while (this.lineCounter != 0);
};