i386/i386.reference/s14_04.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Section 14.4</TITLE>
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   7 <B>up:</B> <A HREF="c14.htm">
   8 Chapter 14 -- 80386 Real-Address Mode</A><BR>
   9 <B>prev:</B> <A HREF="s14_03.htm">14.3  Interrupt and Exception Handling</A><BR>
  10 <B>next:</B> <A HREF="s14_05.htm">14.5  Switching Back to Real-Address Mode</A>
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  14 <H1>14.4  Entering and Leaving Real-Address Mode</H1>
  15 Real-address mode is in effect after a signal on the RESET pin. Even if the
  16 system is going to be used in protected mode, the start-up program will
  17 execute in real-address mode temporarily while initializing for protected
  18 mode.
  19
  20 <H2>14.4.1  Switching to Protected Mode</H2>
  21 The only way to leave real-address mode is to switch to protected mode. The
  22 processor enters protected mode when a
  23 <A HREF="MOVRS.htm">MOV</A> to CR0 instruction sets the PE
  24 (protection enable) bit in CR0. (For compatibility with the 80286, the LMSW
  25 instruction may also be used to set the PE bit.)
  26 <P>
  27 Refer to
  28 <A HREF="c10.htm">Chapter 10</A>
  29    "Initialization" for other aspects of switching to
  30 protected mode.
  31 <P>
  32 <HR>
  33 <P>
  34 <B>up:</B> <A HREF="c14.htm">
  35 Chapter 14 -- 80386 Real-Address Mode</A><BR>
  36 <B>prev:</B> <A HREF="s14_03.htm">14.3  Interrupt and Exception Handling</A><BR>
  37 <B>next:</B> <A HREF="s14_05.htm">14.5  Switching Back to Real-Address Mode</A>
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