hw/i386.reference/POPA.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Opcode POPA</TITLE>
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   6 <BODY>
   7 <B>up:</B> <A HREF="c17.htm">
   8 Chapter 17 -- 80386 Instruction Set</A><BR>
   9 <B>prev:</B><A HREF="POP.htm"> POP Pop a Word from the Stack</A><BR>
  10 <B>next:</B><A HREF="POPF.htm">
  11 POPF/POPFD Pop Stack into FLAGS or EFLAGS Register</A>
  12 <P>
  13 <HR>
  14 <P>
  15 <H1>POPA/POPAD -- Pop all General Registers</H1>
  16
  17 <PRE>
  18 Opcode   Instruction   Clocks   Description
  19
  20 61       POPA          24       Pop DI, SI, BP, SP, BX, DX, CX, and AX
  21 61       POPAD         24       Pop EDI, ESI, EBP, ESP, EDX, ECX, and EAX
  22 </PRE>
  23
  24
  25 <H2>Operation</H2>
  26
  27 <PRE>
  28 IF OperandSize = 16 (* instruction = POPA *)
  29 THEN
  30    DI := Pop();
  31    SI := Pop();
  32    BP := Pop();
  33    throwaway := Pop (); (* Skip SP *)
  34    BX := Pop();
  35    DX := Pop();
  36    CX := Pop();
  37    AX := Pop();
  38 ELSE (* OperandSize = 32, instruction = POPAD *)
  39    EDI := Pop();
  40    ESI := Pop();
  41    EBP := Pop();
  42    throwaway := Pop (); (* Skip ESP *)
  43    EBX := Pop();
  44    EDX := Pop();
  45    ECX := Pop();
  46    EAX := Pop();
  47 FI;
  48 </PRE>
  49
  50 <H2>Description</H2>
  51
  52 POPA pops the eight 16-bit general registers. However, the SP value is
  53 discarded instead of loaded into SP. POPA reverses a previous
  54 <A HREF="PUSHA.htm">PUSHA</A>,
  55 restoring the general registers to their values before
  56 <A HREF="PUSHA.htm">PUSHA</A> was
  57 executed. The first register popped is DI.
  58 <P>
  59 POPAD pops the eight 32-bit general registers. The ESP value is
  60 discarded instead of loaded into ESP. POPAD reverses the previous
  61 <A HREF="PUSHA.htm">PUSHAD</A>,
  62 restoring the general registers to their values before
  63 <A HREF="PUSHA.htm">PUSHAD</A>
  64 was executed. The first register popped is EDI.
  65
  66 <H2>Flags Affected</H2>
  67
  68 None
  69
  70 <H2>Protected Mode Exceptions</H2>
  71
  72 #SS(0) if the starting or ending stack address is not within the stack
  73 segment; #PF(fault-code) for a page fault
  74
  75 <H2>Real Address Mode Exceptions</H2>
  76
  77 Interrupt 13 if any part of the operand would lie outside of the effective
  78 address space from 0 to 0FFFFH
  79
  80 <H2>Virtual 8086 Mode Exceptions</H2>
  81
  82 Same exceptions as in real-address mode; #PF(fault-code) for a page
  83 fault
  84
  85
  86 <P>
  87 <HR>
  88 <P>
  89 <B>up:</B> <A HREF="c17.htm">
  90 Chapter 17 -- 80386 Instruction Set</A><BR>
  91 <B>prev:</B><A HREF="POP.htm"> POP Pop a Word from the Stack</A><BR>
  92 <B>next:</B><A HREF="POPF.htm">
  93 POPF/POPFD Pop Stack into FLAGS or EFLAGS Register</A>
  94 </BODY>