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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html><head><meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1"> <title>ALU</title> <link href="doxygen.css" rel="stylesheet" type="text/css"> </head><body> <!-- Generated by Doxygen 1.2.16 --> <center> <a class="qindex" href="main.html">Main Page</a> <a class="qindex" href="modules.html">Modules</a> <a class="qindex" href="pages.html">Related Pages</a> </center> <hr><h1>ALU<br> <small> [<a class="el" href="group__pavr__pipeline.html">Pipeline details</a>]</small> </h1><table border=0 cellpadding=0 cellspacing=0> </table> <dl compact><dt><b> ALU description</b><dd> The ALU is not a potentially conflicting resource, as it is fully controlled by pipeline stage s5. <br> <br> There are two ALU operands. The first operand is taken either from RF read port 1, if it's an 8 bit operand, or taken from RF read port 1 (lower 8 bits) and from RF read port 2 (higher 8 bits), if it's a 16 bit operand. The second operand is taken either from the RF read port 2 or directly from the instruction opcode; it is always 8 bit-wide. <br> Both operands are fed to the ALU through the Bypass Unit. <br> All ALU-requiring instructions write their result into the Bypass Unit. <br> Details about the ALU hardware resource (connectivity, ALU opcodes) can be found <a class="el" href="group__pavr__hwres__alu.html">here</a>. <br> Instructions that make use of the ALU-related pipeline registers:<ul> <li>ADD, ADC, ADIW<li>SUB, SUBI, SBC, SBCI, SBIW<li>INC, DEC<li>AND, ANDI<li>OR, ORI, EOR<li>COM, NEG, CP, CPC, CPI, SWAP<li>LSR, ROR, ASR<li>MUL, MULS, MULSU<li>FMUL, FMULS, FMULSU<li>MOV, MOVW</ul> </dl><dl compact><dt><b> Plugging the ALU into the pipeline</b><dd> The pipeline registers related to ALU access are presented in the picture below. <br> From this picture, it can also easely figured out instructions' timing. <br> <a name="alu_pipe_ref_01"></a> <br> <div align="center"> <img src="pavr_pipe_alu_01.gif" alt="pavr_pipe_alu_01.gif"> </div> <br> </dl><hr><address align="right"><small>Generated on Tue Dec 31 20:26:31 2002 for Pipelined AVR microcontroller by <a href="http://www.doxygen.org/index.html"> <img src="doxygen.png" alt="doxygen" align="middle" border=0 width=110 height=53></a>1.2.16 </small></address> </body> </html>