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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"><HTML><HEAD><TITLE>80386 Programmer's Reference Manual -- Opcode DAS</TITLE></HEAD><BODY><B>up:</B> <A HREF="c17.htm">Chapter 17 -- 80386 Instruction Set</A><BR><B>prev:</B><A HREF="DAA.htm"> DAA Decimal Adjust AL after Addition</A><BR><B>next:</B><A HREF="DEC.htm"> DEC Decrement by 1</A><P><HR><P><H1>DAS -- Decimal Adjust AL after Subtraction</H1><PRE>Opcode Instruction Clocks Description2F DAS 4 Decimal adjust AL after subtraction</PRE><H2>Operation</H2><PRE>IF (AL AND 0FH) > 9 OR AF = 1THEN AL := AL - 6; AF := 1;ELSE AF := 0;FI;IF (AL > 9FH) OR (CF = 1)THEN AL := AL - 60H; CF := 1;ELSE CF := 0;FI;</PRE><H2>Description</H2>Execute DAS only after a subtraction instruction that leaves atwo-BCD-digit byte result in the AL register. The operands should consistof two packed BCD digits. DAS adjusts AL to contain the correct packedtwo-digit decimal result.<H2>Flags Affected</H2>AF and CF as described above; SF, ZF, and PF as described in <A HREF="appc.htm">Appendix C</A>.<H2>Protected Mode Exceptions</H2>None<H2>Real Address Mode Exceptions</H2>None<H2>Virtual 8086 Mode Exceptions</H2>None<P><HR><P><B>up:</B> <A HREF="c17.htm">Chapter 17 -- 80386 Instruction Set</A><BR><B>prev:</B><A HREF="DAA.htm"> DAA Decimal Adjust AL after Addition</A><BR><B>next:</B><A HREF="DEC.htm"> DEC Decrement by 1</A></BODY>⌨️ 快捷键说明
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