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the border does not change colour per line or char, it changes per frame
Also made the character background dark green or dark orange like suggested.
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‎6847.js‎

Lines changed: 81 additions & 40 deletions
Original file line numberDiff line numberDiff line change
@@ -55,23 +55,35 @@ http://members.casema.nl/hhaydn/howel/logic/6847_clone.htm
5555
64 = 64/8 = 8 8x2bpp = reg1:16 (xscale*2) 0x10
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5757
58+
# Data on PORTA used to set the screen mode; 0x10 means graphics mode, and then 0x20, 0x40, 0x80 are used to set the graphics mode.
59+
# Data on PORTC used to set the colour select bit, which is used in conjunction with the graphics mode bits to select the colour of the screen.
60+
# css = 0 means Black/Green
61+
# css = 1 means Black/Orange
62+
63+
# PORTA is #b000 and PORTC is #b002
64+
# bits 4-7 on #b000 are used to set the graphics mode, )
65+
# and bit 3 on #b002 is used to set the colour select bit. (CSS connected to PC3 on 8255 via)
66+
# eight bits 0-7
67+
68+
5869
// video mode constants
59-
//ppai PORTA
60-
MODE_AG = 0x10; // alpha or graphics
61-
MODE_GM2 = 0x80; // only used if AG is 1
62-
MODE_GM1 = 0x40; // only used if AG is 1
63-
MODE_GM0 = 0x20; // only used if AG is 1
70+
//ppia PORTA
71+
MODE_GM2 = 0x80; // only used if AG is 1 (bit 7)
72+
MODE_GM1 = 0x40; // only used if AG is 1 (bit 6)
73+
MODE_GM0 = 0x20; // only used if AG is 1 (bit 5)
74+
MODE_AG = 0x10; // alpha or graphics (bit 4)
6475
65-
//ppai PORTC
66-
MODE_CSS = 0x08; // colour select
76+
//ppia PORTC
77+
MODE_CSS = 0x08; // colour select (bit 3)
6778
79+
when reading a byte from the VDG, looking at
6880
// WITHIN THE VIDEO MEMORY (bit 6, 6, 7) (AS, INTEXT, INV resp.)
69-
// A/S, INT/EXT, CSS and INV can be changed character by character
70-
// these not used if AG is 1, GM not used if AG is 0
71-
MODE_AS = 0x04;
72-
MODE_INTEXT = 0x02;
73-
MODE_INV = 0x01;
81+
(INT/EXT & A/S connected to D6, and INV connected to D7 from CPU
7482
83+
This means D6 switches between internal alphanumeric, and semigraphics 6 (SG6)
84+
85+
// A/S-INT/EXT, INV can be changed character by character, and CSS on interrupt from CPU
86+
// these not used if AG is 1, GM not used if AG is 0
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for bits
7789
@@ -96,6 +108,9 @@ only 1 bit is used of SG6 - to get yellow/red, cyan/orange
96108
// MODE_GM1 = 0x20,
97109
// MODE_GM0 = 0x10;
98110

111+
// constant for the graphics mode
112+
const MODE_AG = 0x10; // graphics mode
113+
99114
export function Video6847(video) {
100115
this.video = video;
101116
this.levelDEW = false;
@@ -105,9 +120,21 @@ export function Video6847(video) {
105120
//
106121
this.collook = utils.makeFast32(
107122
new Uint32Array([
108-
0xff000000, 0xff00ff00, 0xff00ffff, 0xffff0000, 0xff0000ff, 0xffffffff, 0xffffff00, 0xffff00ff, 0xff0080ff,
123+
0xff000000, // #00000000, // black
124+
0xff03b91e, // #00ff00, // green
125+
0xff00ffff, // #ffff00, // yellow
126+
0xffff083b, // #3b08ff, // blue
127+
0xff0516b9, // #b91605, // red
128+
0xff018eb4, // #b48e01, // buff
129+
0xffeb9200, // #0092eb, // cyan
130+
0xffff1cff, // #ff1cff, // magenta
131+
0xff005bbd, // #bd5b00, // orange
132+
133+
0xff000600, // dark green (char background) #000600
134+
0xff000d1c, // dark orange (char background) #1c0d00
109135
])
110136
);
137+
111138
// { 0, 0, 0 }, /*Black 0*/
112139
// { 0, 63, 0 }, /*Green 1*/
113140
// { 63, 63, 0 }, /*Yellow 2*/
@@ -116,7 +143,10 @@ export function Video6847(video) {
116143
// { 63, 63, 63 }, /*Buff 5*/
117144
// { 0, 63, 63 }, /*Cyan 6*/
118145
// { 63, 0, 63 }, /*Magenta 7*/
119-
// { 63, 32, 0 }, /*Orange 8 - actually red on the Atom*/
146+
// { 63, 32, 0 }, /*Orange 8 - can be red on the Atom*/
147+
148+
// /* dark green 9 */
149+
// /* dark orange 10 */
120150

121151
this.regs = new Uint8Array(32);
122152
this.bitmapX = 0;
@@ -272,11 +302,16 @@ export function Video6847(video) {
272302
this.vdg_cycles = 0;
273303
this.charTime = 0;
274304

305+
this.bordercolour = 0x00; // 0x00 black 0x01 // green or orange depending on CSS
306+
275307
// ATOM uses 6847 chip
276308
this.polltime = function (clocks) {
277309
var mode = this.ppia.portapins & 0xf0;
278310
var css = (this.ppia.portcpins & 0x08) >>> 2;
279311
this.setValuesFromMode(mode);
312+
// Note: Polltime is called from the CPU many times during a frame. Once the VDG has drawn a bit of a frame
313+
// it returns, and then comes back here later to continue the same frame. That's how the snow is able to work
314+
// it doesn't draw the whole frame. It regularly gives control back to the CPU.
280315

281316
var vdgcharclock = this.pixelsPerChar / 2; // 4 or 8
282317
var vdgclock = 3.638004; // This ought to be 3.579545, but this looks better with the INTs being used.
@@ -399,6 +434,13 @@ export function Video6847(video) {
399434
// );
400435
// this.lastseconds = seconds ?? 0;
401436
// }
437+
438+
// fix the border colour at the end/start of a frame
439+
// it won't change within a frame
440+
let AGM = (mode & MODE_AG) === 0;
441+
442+
if (AGM) this.bordercolour = 0x00; // black
443+
else this.bordercolour = 0x01; // green orange
402444
}
403445

404446
if (nextChar) {
@@ -415,26 +457,17 @@ export function Video6847(video) {
415457
{
416458
// TODO: Add in the INTEXT modifiers to mode (if necessary)
417459
// blit into the fb32 buffer which is painted by VIDEO
418-
if ((mode & 0x10) === 0)
460+
if ((mode & MODE_AG) === 0)
419461
// MODE_AG - bit 4; 0x10 is the AG bit
420462
this.blitChar(this.video.fb32, dat, offset, this.pixelsPerChar, css);
421463
else this.blitPixels(this.video.fb32, dat, offset, css);
422464
}
423465
}
424466
} else {
425-
let dat = 0xff;
426-
// var insideTopBottomBorder = (this.dispEnabled & (HDISPENABLE | VDISPENABLE)) === (VDISPENABLE);
427-
// dat = 0x2f;
428-
// if (insideTopBottomBorder)
429-
// dat = 0x11;
430-
431467
// draw BLACK in the border
432468
let offset = this.bitmapY;
433469
offset = offset * 1024 + this.bitmapX;
434-
if ((mode & 0x10) === 0)
435-
// MODE_AG - bit 4; 0x10 is the AG bit
436-
this.blitChar(this.video.fb32, 0x20, offset, this.pixelsPerChar, css);
437-
else this.blitPixels(this.video.fb32, dat, offset, css);
470+
this.blitBorder(this.video.fb32, this.bordercolour, offset, css);
438471
}
439472

440473
this.addr = (this.addr + 1) & 0x1fff;
@@ -489,6 +522,24 @@ export function Video6847(video) {
489522
} // matches while
490523
};
491524

525+
this.blitBorder = function (buf, data, destOffset, css) {
526+
var bpp = this.bpp;
527+
var pixelsPerBit = this.pixelsPerBit / bpp;
528+
var numPixels = 8 * pixelsPerBit; //per char
529+
var fb32 = buf;
530+
var i = 0;
531+
for (i = 0; i < numPixels; ++i) {
532+
var n = numPixels - 1 - i; // pixels in reverse order
533+
534+
var colour = this.collook[css ? 5 : 1]; // buff or green
535+
if (data === 0x00) {
536+
colour = this.collook[0]; // black
537+
}
538+
fb32[destOffset + n] = fb32[destOffset + n + 1024] = // two lines
539+
colour;
540+
}
541+
};
542+
492543
this.blitPixels = function (buf, data, destOffset, css) {
493544
// var scanline = this.scanlineCounterT;
494545
// bitpattern from data is either 4 or 8 pixels in raw graphics
@@ -519,16 +570,6 @@ export function Video6847(video) {
519570
// get bits in pairs or singles
520571
var j = Math.floor(i / pixelsPerBit);
521572

522-
// { 0, 0, 0 }, /*Black 0*/
523-
// { 0, 63, 0 }, /*Green 1*/
524-
// { 63, 63, 0 }, /*Yellow 2*/
525-
// { 0, 0, 63 }, /*Blue 3 */
526-
// { 63, 0, 0 }, /*Red 4 */
527-
// { 63, 63, 63 }, /*Buff 5*/
528-
// { 0, 63, 63 }, /*Cyan 6*/
529-
// { 63, 0, 63 }, /*Magenta 7*/
530-
// { 63, 32, 0 }, /*Orange 8 - actually red on the Atom*/
531-
532573
// get just one bit
533574
// RG modes
534575
if (bpp === 1) {
@@ -560,10 +601,10 @@ export function Video6847(video) {
560601

561602
// character set is just the pixel data
562603
// 0 - 63 is alphachars green (0x00-0x3f) bits 0-5 for character
563-
// 64-127 is alphagraphics green/yellow/blue/red (0x40-0x7f) bit 6,7 (0xC0)
604+
// 64-127 is 16 alphagraphics in 4 colours green/yellow/blue/red (0x40-0x7f) bit 6,7 (0xC0)
564605
// bit 7 set is inverted and the alphagraphics again
565606
// 128 - 191 is alphachars inverted green (0x80-0xbf)
566-
// 192-255 is alphagraphics again buff/cyan/magenta/orange (0xc0-0xff) bit 6,7 set (0xC0)
607+
// 192-255 is alphagraphics in different colours buff/cyan/magenta/orange (0xc0-0xff) bit 6,7 set (0xC0)
567608

568609
// in the data; bits 0-5 are the pixels
569610
// bit 7 and CSS give the colour
@@ -598,9 +639,9 @@ export function Video6847(video) {
598639
for (i = 0; i < numPixels; ++i) {
599640
var n = numPixels - 1 - i; // pixels in reverse order
600641
var j = i / pixelsPerBit;
601-
// text is either green/black or orange/black - nothing else
642+
// text is either green/black or buff/black - nothing else
602643
// css is 2 or 0 on input
603-
var fgcol = this.collook[css ? 8 : 1];
644+
var fgcol = this.collook[css ? 5 : 1];
604645

605646
if (agmode) {
606647
// alphagraphics 6
@@ -614,7 +655,7 @@ export function Video6847(video) {
614655
}
615656

616657
var luminance = (chardef >>> j) & 0x1;
617-
var colour = luminance ? fgcol : this.collook[0];
658+
var colour = luminance ? fgcol : this.collook[css ? 10 : 9]; //dark orange or green
618659
fb32[destOffset + n] = fb32[destOffset + n + 1024] = // two lines
619660
colour;
620661
}

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