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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"><HTML><HEAD><TITLE>80386 Programmer's Reference Manual -- Opcode CLTS</TITLE></HEAD><BODY><B>up:</B> <A HREF="c17.htm">Chapter 17 -- 80386 Instruction Set</A><BR><B>prev:</B><A HREF="CLI.htm"> CLI Clear Interrupt Flag</A><BR><B>next:</B><A HREF="CMC.htm"> CMC Complement Carry Flag</A><P><HR><P><H1>CLTS -- Clear Task-Switched Flag in CR0</H1><PRE>Opcode Instruction Clocks DescriptionOF 06 CLTS 5 Clear task-switched flag</PRE><H2>Operation</H2><PRE>TS Flag in CR0 := 0;</PRE><H2>Description</H2>CLTS clears the task-switched (TS) flag in register CR0. This flag is set bythe 80386 every time a task switch occurs. The TS flag is used to manageprocessor extensions as follows:<UL> <LI> Every execution of an ESC instruction is trapped if the TS flag is set. <LI> Execution of a WAIT instruction is trapped if the MP flag and the TS flag are both set.</UL>Thus, if a task switch was made after an ESC instruction was begun, theprocessor extension's context may need to be saved before a new ESCinstruction can be issued. The fault handler saves the context and resetsthe TS flag.<P>CLTS appears in operating system software, not in application programs. Itis a privileged instruction that can only be executed at privilege level 0.<H2>Flags Affected</H2>TS := 0 (TS is in CR0, not the flag register)<H2>Protected Mode Exceptions</H2>#GP(0) if CLTS is executed with a current privilege level other than 0<H2>Real Address Mode Exceptions</H2>None (valid in Real Address Mode to allow initialization for ProtectedMode)<H2>Virtual 8086 Mode Exceptions</H2>Same exceptions as in Real Address Mode<P><HR><P><B>up:</B> <A HREF="c17.htm">Chapter 17 -- 80386 Instruction Set</A><BR><B>prev:</B><A HREF="CLI.htm"> CLI Clear Interrupt Flag</A><BR><B>next:</B><A HREF="CMC.htm"> CMC Complement Carry Flag</A></BODY>⌨️ 快捷键说明
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