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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><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 Description61 POPA 24 Pop DI, SI, BP, SP, BX, DX, CX, and AX61 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 isdiscarded 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> wasexecuted. The first register popped is DI.<P>POPAD pops the eight 32-bit general registers. The ESP value isdiscarded 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 stacksegment; #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 effectiveaddress space from 0 to 0FFFFH<H2>Virtual 8086 Mode Exceptions</H2>Same exceptions as in real-address mode; #PF(fault-code) for a pagefault<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>⌨️ 快捷键说明
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