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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"><HTML><HEAD><TITLE>80386 Programmer's Reference Manual -- Section 14.4</TITLE></HEAD><BODY><B>up:</B> <A HREF="c14.htm">Chapter 14 -- 80386 Real-Address Mode</A><BR><B>prev:</B> <A HREF="s14_03.htm">14.3 Interrupt and Exception Handling</A><BR><B>next:</B> <A HREF="s14_05.htm">14.5 Switching Back to Real-Address Mode</A><P><HR><P><H1>14.4 Entering and Leaving Real-Address Mode</H1>Real-address mode is in effect after a signal on the RESET pin. Even if thesystem is going to be used in protected mode, the start-up program willexecute in real-address mode temporarily while initializing for protectedmode.<H2>14.4.1 Switching to Protected Mode</H2>The only way to leave real-address mode is to switch to protected mode. Theprocessor enters protected mode when a <A HREF="MOVRS.htm">MOV</A> to CR0 instruction sets the PE(protection enable) bit in CR0. (For compatibility with the 80286, the LMSWinstruction may also be used to set the PE bit.)<P>Refer to <A HREF="c10.htm">Chapter 10</A> "Initialization" for other aspects of switching toprotected mode.<P><HR><P><B>up:</B> <A HREF="c14.htm">Chapter 14 -- 80386 Real-Address Mode</A><BR><B>prev:</B> <A HREF="s14_03.htm">14.3 Interrupt and Exception Handling</A><BR><B>next:</B> <A HREF="s14_05.htm">14.5 Switching Back to Real-Address Mode</A></BODY>⌨️ 快捷键说明
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