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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>Returns</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>Returns<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> A few details</b><dd> There are two kinds of returns: <ul> <li> RET <br> Return from subroutine. <br> The Program Counter is loaded with the return address (22 bit wide) read from the stack, and the Stack Pointer is incremented by 3. <li> RETI <br> The same as RET, but in addition sets the general interrupt flag (flag I in the Status Register). </ul> <br> Returns are the slowest instructions in the pAVR implementation of the AVR instruction set. They take 9 clocks. <br> First 2 clocks are spent while waiting the previous instructions to write the Unified Memory. Next 5 clocks, the Program Counter is read from the Unified Memory. In a future version, this part might take only 4 clocks. Finally, another 2 clocks are spent while bringing the target instruction into the instruction register. <br> <br> <div align="center"> <img src="pavr_pipe_returns_01.gif" alt="pavr_pipe_returns_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>