161 lines
4.2 KiB
HTML
161 lines
4.2 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html><head><title>NES Scrolling 2</title>
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<meta http-equiv="Content-Style-Type" content="text/css">
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<style type="text/css"><!--
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body {
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margin: 5px 5px 5px 5px;
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background-color: #ffffff;
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}
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/* ========== Text Styles ========== */
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hr { color: #000000}
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body, table /* Normal text */
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{
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font-size: 10pt;
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font-family: 'Arial', 'Helvetica', sans-serif;
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font-style: normal;
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font-weight: normal;
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color: #000000;
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text-decoration: none;
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;
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}
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span.rvts1 /* Heading */
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{
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font-weight: bold;
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color: #0000ff;
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}
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span.rvts2 /* Subheading */
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{
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font-weight: bold;
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color: #000080;
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}
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span.rvts3 /* Keywords */
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{
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font-style: italic;
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color: #800000;
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}
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a.rvts4, span.rvts4 /* Jump 1 */
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{
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color: #008000;
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text-decoration: underline;
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}
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a.rvts5, span.rvts5 /* Jump 2 */
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{
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color: #008000;
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text-decoration: underline;
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}
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span.rvts6 /* Font Hint */
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{
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color: #808080;
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}
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span.rvts7 /* Font Hint Title */
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{
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font-size: 15pt;
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font-family: 'Tahoma', 'Geneva', sans-serif;
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font-weight: bold;
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color: #404040;
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}
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span.rvts8 /* Font Hint Bold */
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{
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font-weight: bold;
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color: #808080;
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}
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span.rvts9 /* Font Hint Italic */
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{
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font-style: italic;
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color: #808080;
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}
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span.rvts10 /* Font Style */
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{
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font-size: 16pt;
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font-family: 'Tahoma', 'Geneva', sans-serif;
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color: #ffffff;
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}
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span.rvts11 /* Font Style */
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{
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font-family: 'MS Sans Serif', 'Geneva', sans-serif;
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color: #808080;
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}
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span.rvts12 /* Font Style */
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{
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font-family: 'Verdana', 'Geneva', sans-serif;
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font-style: italic;
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color: #c0c0c0;
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}
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a.rvts13, span.rvts13 /* Font Style */
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{
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font-family: 'Verdana', 'Geneva', sans-serif;
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font-style: italic;
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color: #6666ff;
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text-decoration: underline;
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}
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/* ========== Para Styles ========== */
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p,ul,ol /* Paragraph Style */
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{
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text-align: left;
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text-indent: 0px;
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padding: 0px 0px 0px 0px;
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margin: 0px 0px 0px 0px;
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}
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.rvps1 /* Centered */
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{
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text-align: center;
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}
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.rvps2 /* Paragraph Style */
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{
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background: #9fbed0;
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margin: 0px 0px 20px 0px;
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}
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.rvps3 /* Paragraph Style */
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{
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text-align: center;
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background: #e4e4e4;
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margin: 20px 0px 0px 0px;
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}
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.rvps4 /* Paragraph Style */
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{
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border-color: #c0c0c0;
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border-style: solid;
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border-width: 1px;
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border-right: none;
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border-bottom: none;
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border-left: none;
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background: #ffffff;
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padding: 3px 0px 0px 0px;
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margin: 27px 0px 0px 0px;
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}
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--></style>
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<script type="text/javascript">if(top.frames.length == 0) { top.location.href="../fceux-2.0.2.htm?{33EA1433-5AF2-4DE5-99C6-A073ECA7861A}.htm"; }</script>
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<meta name="generator" content="HelpNDoc Free"></head>
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<body>
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<p class=rvps2><span class=rvts10>NES Scrolling 2</span></p>
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<p>nes scrolling</p>
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<p><br></p>
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<p>Date: Tue, 13 Apr 1999 17:48:54 -0600</p>
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<p>From: loopy <zxcvzxcv@netzero.net></p>
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<p>Reply-To: nesdev@onelist.com</p>
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<p>To: nesdev@onelist.com</p>
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<p><br></p>
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<p>From: loopy <zxcvzxcv@netzero.net></p>
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<p><br></p>
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<p>(more notes on ppu logic)</p>
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<p><br></p>
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<p>you can think of bits 0,1,2,3,4 of the vram address as the "x scroll"(*8)</p>
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<p>that the ppu increments as it draws. as it wraps from 31 to 0, bit 10 is</p>
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<p>switched. you should see how this causes horizontal wrapping between name</p>
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<p>tables (0,1) and (2,3).</p>
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<p><br></p>
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<p>you can think of bits 5,6,7,8,9 as the "y scroll"(*8). this functions</p>
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<p>slightly different from the X. it wraps to 0 and bit 11 is switched when</p>
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<p>it's incremented from _29_ instead of 31. there are some odd side effects</p>
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<p>from this.. if you manually set the value above 29 (from either 2005 or</p>
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<p>2006), the wrapping from 29 obviously won't happen, and attrib data will be</p>
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<p>used as name table data. the "y scroll" still wraps to 0 from 31, but</p>
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<p>without switching bit 11. this explains why writing 240+ to 'Y' in 2005</p>
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<p>appeared as a negative scroll value.</p>
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<p><br></p>
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<p class=rvps3><span class=rvts11>2008</span></p>
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<p class=rvps4><span class=rvts12>This help file has been generated by the freeware version of </span><a class=rvts13 href="http://www.ibe-software.com/products/software/helpndoc/" target="_blank">HelpNDoc</a></p>
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</body></html>
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