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91 lines
3.1 KiB
HTML
Vendored
91 lines
3.1 KiB
HTML
Vendored
<HTML>
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<HEAD>
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<META NAME="GENERATOR" CONTENT="Adobe PageMill 3.0 Win">
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<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
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<TITLE>6502 Architecture</TITLE>
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<LINK REL="StyleSheet" HREF="../obelisk.css" TYPE="text/css" media="screen,print">
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</HEAD>
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<BODY>
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<script type="text/javascript"><!--
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google_ad_client = "pub-0826595092783671";
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/* 6502 Header */
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google_ad_slot = "9208748029";
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google_ad_width = 728;
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google_ad_height = 90;
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//-->
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</script>
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<script type="text/javascript"
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src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
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</script>
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<HR>
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<H2>Basic Architecture</H2>
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<P>The 6502 microprocessor is a relatively simple 8 bit CPU with
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only a few internal registers capable of addressing at most 64Kb
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of memory via its 16 bit address bus. The processor is little
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endian and expects addresses to be stored in memory least significant
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byte first.</P>
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<P>The first 256 byte page of memory ($0000-$00FF) is referred
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to as 'Zero Page' and is the focus of a number of special addressing
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modes that result in shorter (and quicker) instructions or allow
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indirect access to the memory. The second page of memory ($0100-$01FF)
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is reserved for the system stack and which cannot be relocated.</P>
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<P>The only other reserved locations in the memory map are the
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very last 6 bytes of memory $FFFA to $FFFF which must be programmed
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with the addresses of the non-maskable interrupt handler ($FFFA/B),
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the power on reset location ($FFFC/D) and the BRK/interrupt request
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handler ($FFFE/F) respectively.</P>
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<P>The 6502 does not have any special support of hardware devices
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so they must be mapped to regions of memory in order to exchange
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data with the hardware latches.</P>
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<P><TABLE BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%"
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HEIGHT="30">
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<TR>
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<TD WIDTH="25%" BGCOLOR="#aaaaff"> <A HREF="index.html"><<
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Back</A></TD>
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<TD WIDTH="25%" BGCOLOR="#aaaaff">
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<P><CENTER><A HREF="../index.html" TARGET="_parent">Home</A></CENTER></TD>
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<TD WIDTH="25%" BGCOLOR="#aaaaff">
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<P><CENTER><A HREF="index.html">Contents</A></CENTER></TD>
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<TD ALIGN="RIGHT" WIDTH="25%" BGCOLOR="#aaaaff"><A HREF="registers.html">Next
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>></A></TD>
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</TR>
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</TABLE></P>
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<P>
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<HR>
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<script type="text/javascript"><!--
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google_ad_client = "pub-0826595092783671";
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/* 6502 Footer */
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google_ad_slot = "9966603696";
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google_ad_width = 728;
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google_ad_height = 90;
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//-->
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</script>
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<script type="text/javascript"
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src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
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</script>
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<HR>
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<script type="text/javascript"><!--
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google_ad_client = "pub-0826595092783671";
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/* 6502 Links */
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google_ad_slot = "4173075094";
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google_ad_width = 728;
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google_ad_height = 15;
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//-->
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</script>
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<script type="text/javascript"
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src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
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</script>
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<script type="text/javascript">
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} catch(err) {}</script>
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<HR ALIGN=LEFT>This page was last updated on 2nd January 2002
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</BODY>
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</HTML>
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