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POPA.htm
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POPA.htm
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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HTML>
<HEAD>
<TITLE>80386 Programmer's Reference Manual -- Opcode POPA</TITLE>
</HEAD>
<BODY STYLE="width:80ch">
<B>up:</B> <A HREF="c17.htm">
Chapter 17 -- 80386 Instruction Set</A><BR>
<B>prev:</B><A HREF="POP.htm"> POP Pop a Word from the Stack</A><BR>
<B>next:</B><A HREF="POPF.htm">
POPF/POPFD Pop Stack into FLAGS or EFLAGS Register</A>
<P>
<HR>
<P>
<H1>POPA/POPAD -- Pop all General Registers</H1>
<PRE>
Opcode Instruction Clocks Description
61 POPA 24 Pop DI, SI, BP, SP, BX, DX, CX, and AX
61 POPAD 24 Pop EDI, ESI, EBP, ESP, EDX, ECX, and EAX
</PRE>
<H2>Operation</H2>
<PRE>
IF OperandSize = 16 (* instruction = POPA *)
THEN
DI := Pop();
SI := Pop();
BP := Pop();
throwaway := Pop (); (* Skip SP *)
BX := Pop();
DX := Pop();
CX := Pop();
AX := Pop();
ELSE (* OperandSize = 32, instruction = POPAD *)
EDI := Pop();
ESI := Pop();
EBP := Pop();
throwaway := Pop (); (* Skip ESP *)
EBX := Pop();
EDX := Pop();
ECX := Pop();
EAX := Pop();
FI;
</PRE>
<H2>Description</H2>
POPA pops the eight 16-bit general registers. However, the SP value is
discarded instead of loaded into SP. POPA reverses a previous
<A HREF="PUSHA.htm">PUSHA</A>,
restoring the general registers to their values before
<A HREF="PUSHA.htm">PUSHA</A> was
executed. The first register popped is DI.
<P>
POPAD pops the eight 32-bit general registers. The ESP value is
discarded instead of loaded into ESP. POPAD reverses the previous
<A HREF="PUSHA.htm">PUSHAD</A>,
restoring the general registers to their values before
<A HREF="PUSHA.htm">PUSHAD</A>
was executed. The first register popped is EDI.
<H2>Flags Affected</H2>
None
<H2>Protected Mode Exceptions</H2>
#SS(0) if the starting or ending stack address is not within the stack
segment; #PF(fault-code) for a page fault
<H2>Real Address Mode Exceptions</H2>
Interrupt 13 if any part of the operand would lie outside of the effective
address space from 0 to 0FFFFH
<H2>Virtual 8086 Mode Exceptions</H2>
Same exceptions as in real-address mode; #PF(fault-code) for a page
fault
<P>
<HR>
<P>
<B>up:</B> <A HREF="c17.htm">
Chapter 17 -- 80386 Instruction Set</A><BR>
<B>prev:</B><A HREF="POP.htm"> POP Pop a Word from the Stack</A><BR>
<B>next:</B><A HREF="POPF.htm">
POPF/POPFD Pop Stack into FLAGS or EFLAGS Register</A>
</BODY>