8086_instruction_set.html

嵌入式C++开发环境 模拟器 可以帮助你调试开发环境 提高工作效率

<TR>
<TD>
<FONT FACE="Fixedsys">
CMP
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>
	REG, memory<BR>
	memory, REG<BR>
	REG, REG<BR>
	memory, immediate<BR>
	REG, immediate
	</NOBR>
</FONT>
</TD>
<TD>

Compare.
<BR><BR>Algorithm:<BR><BR>
<FONT FACE="Fixedsys">
operand1 - operand2
<BR><BR>
result is not stored anywhere, flags are set (OF, SF, ZF, AF, PF, CF) according
to result.
</FONT>
<BR><BR>Example:<PRE><FONT FACE="Fixedsys">MOV AL, 5
MOV BL, 5
CMP AL, BL  ; AL = 5, ZF = 1 (so equal!)
RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> </TR>
</TABLE>
</FONT>

			<A NAME="CMPSB">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
CMPSB
</FONT>
</TD>
<TD>No operands</TD>
<TD>

Compare bytes: <NOBR>ES:[DI] from DS:[SI].</NOBR> <BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>DS:[SI] - ES:[DI]<BR></LI>
<LI>set flags according to result:<BR> OF, SF, ZF, AF, PF, CF<BR></LI>
<LI>if DF = 0 then
	<UL>
	<LI>SI = SI + 1</LI>
	<LI>DI = DI + 1</LI>
	</UL>
	else
	<UL>
	<LI>SI = SI - 1</LI>
	<LI>DI = DI - 1</LI>
	</UL>
</LI>
</UL>
</FONT>
Example:<BR>
see <B><A HREF="../Samples/cmpsb.asm">cmpsb.asm</A></B> in Samples.

<BR><BR>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> </TR>
</TABLE>
</FONT>

			<A NAME="CMPSW">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
CMPSW
</FONT>
</TD>
<TD>No operands</TD>
<TD>

Compare words: <NOBR>ES:[DI] from DS:[SI].</NOBR> <BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>DS:[SI] - ES:[DI]<BR></LI>
<LI>set flags according to result:<BR> OF, SF, ZF, AF, PF, CF<BR></LI>
<LI>if DF = 0 then
	<UL>
	<LI>SI = SI + 2</LI>
	<LI>DI = DI + 2</LI>
	</UL>
	else
	<UL>
	<LI>SI = SI - 2</LI>
	<LI>DI = DI - 2</LI>
	</UL>
</LI>
</UL>
</FONT>
Example:<BR>
see <B><A HREF="../Samples/cmpsw.asm">cmpsw.asm</A></B> in Samples.

<BR><BR>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> </TR>
</TABLE>
</FONT>

			<A NAME="CWD">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
CWD
</FONT>
</TD>
<TD>No operands</TD>
<TD>

Convert Word to Double word. <BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
if high bit of AX = 1 then:
<UL>
<LI>DX = 65535 (0FFFFh)</LI>
</UL>
<BR>
else
<UL>
<LI>DX = 0</LI>
</UL>
</FONT>
<BR>Example:<PRE><FONT FACE="Fixedsys">MOV DX, 0   ; DX = 0
MOV AX, 0   ; AX = 0
MOV AX, -5  ; DX AX = 00000h:0FFFBh
CWD         ; DX AX = 0FFFFh:0FFFBh
RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD COLSPAN=6>unchanged</TD> </TR>
</TABLE>
</FONT>

			<A NAME="DAA">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
DAA
</FONT>
</TD>
<TD>No operands</TD>
<TD>

Decimal adjust After Addition.<BR>
Corrects the result of addition of two packed BCD values. <BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
if low nibble of AL > 9 or AF = 1 then:<BR>
<UL>
<LI>AL = AL + 6</LI>
<LI>AF = 1</LI>
</UL>
if AL > 9Fh or CF = 1 then:
<UL>
<LI>AL = AL + 60h</LI>
<LI>CF = 1</LI>
</UL>
</FONT>
<BR>Example:<PRE><FONT FACE="Fixedsys">MOV AL, 0Fh  ; AL = 0Fh (15)
DAA          ; AL = 15h
RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> </TR>
</TABLE>
</FONT>

			<A NAME="DAS">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
DAS
</FONT>
</TD>
<TD>No operands</TD>
<TD>

Decimal adjust After Subtraction.<BR>
Corrects the result of subtraction of two packed BCD values. <BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
if low nibble of AL > 9 or AF = 1 then:<BR>
<UL>
<LI>AL = AL - 6</LI>
<LI>AF = 1</LI>
</UL>
if AL > 9Fh or CF = 1 then:
<UL>
<LI>AL = AL - 60h</LI>
<LI>CF = 1</LI>
</UL>
</FONT>
<BR>Example:<PRE><FONT FACE="Fixedsys">MOV AL, 0FFh  ; AL = 0FFh (-1)
DAS           ; AL = 99h, CF = 1
RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> </TR>
</TABLE>
</FONT>

			<A NAME="DEC">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
DEC
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>
	REG<BR>
	memory<BR>
	</NOBR>
</FONT>
</TD>
<TD>

Decrement.
<BR><BR>Algorithm:<BR><BR>
<FONT FACE="Fixedsys">
operand = operand - 1
<BR><BR>
</FONT>
<BR>Example:<PRE><FONT FACE="Fixedsys">MOV AL, 255  ; AL = 0FFh (255 or -1)
DEC AL       ; AL = 0FEh (254 or -2)
RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> </TR>
</TABLE>
CF - unchanged!
</FONT>

			<A NAME="DIV">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
DIV
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>
	REG<BR>
	memory<BR>
	</NOBR>
</FONT>
</TD>
<TD>

Unsigned divide.
<BR><BR>Algorithm:<BR><BR>
 <BLOCKQUOTE>
	 when operand is a <B>byte</B>:<BR>
	 <FONT FACE="Fixedsys">AL = AX / operand<BR>
	 AH = remainder (modulus)
	 </FONT>
 </BLOCKQUOTE>

 <BLOCKQUOTE>
	when operand is a <B>word</B>:<BR>
	<FONT FACE="Fixedsys">AX = (DX AX) / operand<BR>
	DX = remainder (modulus)
	</FONT>
 </BLOCKQUOTE>
 Example:<PRE><FONT FACE="Fixedsys">MOV AX, 203   ; AX = 00CBh
MOV BL, 4
DIV BL        ; AL = 50 (32h), AH = 3
RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD>?</TD> <TD>?</TD> <TD>?</TD> <TD>?</TD> <TD>?</TD> <TD>?</TD> </TR>
</TABLE>
</FONT>

 			<A NAME="HLT">&nbsp;</A>
</TD>
</TR>






<TR>
<TD>
<FONT FACE="Fixedsys">
HLT
</FONT>
</TD>
<TD>No operands</TD>
<TD>

Halt the System.<BR><BR>

 Example:<PRE><FONT FACE="Fixedsys">MOV AX, 5
HLT</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD COLSPAN=6>unchanged</TD> </TR>
</TABLE>
</FONT>

 			<A NAME="IDIV">&nbsp;</A>
</TD>
</TR>





<TR>
<TD>
<FONT FACE="Fixedsys">
IDIV
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>
	REG<BR>
	memory<BR>
	</NOBR>
</FONT>
</TD>
<TD>

Signed divide.
<BR><BR>Algorithm:<BR><BR>
 <BLOCKQUOTE>
	 when operand is a <B>byte</B>:<BR>
	 <FONT FACE="Fixedsys">AL = AX / operand<BR>
	 AH = remainder (modulus)
	 </FONT>
 </BLOCKQUOTE>

 <BLOCKQUOTE>
	when operand is a <B>word</B>:<BR>
	<FONT FACE="Fixedsys">AX = (DX AX) / operand<BR>
	DX = remainder (modulus)
	</FONT>
 </BLOCKQUOTE>
 Example:<PRE><FONT FACE="Fixedsys">MOV AX, -203 ; AX = 0FF35h
MOV BL, 4
IDIV BL      ; AL = -50 (0CEh), AH = -3 (0FDh)
RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD>?</TD> <TD>?</TD> <TD>?</TD> <TD>?</TD> <TD>?</TD> <TD>?</TD> </TR>
</TABLE>
</FONT>

 			<A NAME="IMUL">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
IMUL
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>
	REG<BR>
	memory<BR>
	</NOBR>
</FONT>
</TD>
<TD>

Signed multiply.
<BR><BR>Algorithm:<BR><BR>
 <BLOCKQUOTE>
	 when operand is a <B>byte</B>:<BR>
	 <FONT FACE="Fixedsys">AX = AL * operand</FONT>.
 </BLOCKQUOTE>

 <BLOCKQUOTE>
	when operand is a <B>word</B>:<BR>
	<FONT FACE="Fixedsys">(DX AX) = AX * operand</FONT>.
 </BLOCKQUOTE>
  Example:<PRE><FONT FACE="Fixedsys">MOV AL, -2
MOV BL, -4
IMUL BL      ; AX = 8
RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD>r</TD> <TD>?</TD> <TD>?</TD> <TD>r</TD> <TD>?</TD> <TD>?</TD> </TR>
</TABLE>
CF=OF=0 when result fits into operand of IMUL.
</FONT>

 			<A NAME="IN">&nbsp;</A>
</TD>
</TR>


<TR>
<TD>
<FONT FACE="Fixedsys">
IN
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>
	AL, im.byte<BR>
	AL, DX<BR>
	AX, im.byte<BR>
	AX, DX
	</NOBR>
</FONT>
</TD>
<TD>

Input from port into <B>AL</B> or <B>AX</B>.<BR>
Second operand is a port number. If required to access
port number over 255 - <B>DX</B> register should be used.
<BR>Example:<PRE><FONT FACE="Fixedsys">IN AX, 4  ; get status of traffic lights.
IN AL, 7  ; get status of stepper-motor.
</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD COLSPAN=6>unchanged</TD> </TR>
</TABLE>
</FONT>

 			<A NAME="INC">&nbsp;</A>
</TD>
</TR>


<TR>
<TD>
<FONT FACE="Fixedsys">
INC
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>
	REG<BR>
	memory<BR>
	</NOBR>
</FONT>
</TD>
<TD>

Increment.
<BR><BR>Algorithm:<BR><BR>
<FONT FACE="Fixedsys">
operand = operand + 1
<BR>
</FONT>
<BR>Example:<PRE><FONT FACE="Fixedsys">MOV AL, 4
INC AL       ; AL = 5
RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> <TD>r</TD> </TR>
</TABLE>
CF - unchanged!
</FONT>

			<A NAME="INT">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
INT
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>immediate byte</NOBR>
</FONT>
</TD>
<TD>

Interrupt numbered by immediate byte (0..255).
<BR><BR>Algorithm:<BR><BR>
<FONT FACE="Fixedsys">
<UL>
	Push to stack:
	<UL>
	<LI>flags register</LI>
	<LI>CS</LI>
	<LI>IP</LI>
	</UL>

	<LI>IF = 0</LI>

	<LI>Transfer control to interrupt procedure</LI>
</UL>
</FONT>
<BR>Example:<PRE><FONT FACE="Fixedsys">MOV AH, 0Eh  ; teletype.
MOV AL, 'A'
INT 10h      ; BIOS interrupt.
RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> <TD>I</TD> </TR>
<TR> <TD COLSPAN=6>unchanged</TD> <TD>0</TD></TR>
</TABLE>
</FONT>

			<A NAME="INTO">&nbsp;</A>
</TD>
</TR>



<TR>
<TD>
<FONT FACE="Fixedsys">
INTO
</FONT>
</TD>
<TD>No operands</TD>
<TD>

Interrupt 4 if Overflow flag is 1.
<BR><BR>Algorithm:<BR><BR>
<FONT FACE="Fixedsys">
if OF = 1 then INT 4
<BR>
</FONT>
<BR>Example:<PRE><FONT FACE="Fixedsys">; -5 - 127 = -132 (not in -128..127)
; the result of SUB is wrong (124),
; so OF = 1 is set:
MOV AL, -5
SUB AL, 127   ; AL = 7Ch (124)
INTO          ; process error.
RET</FONT></PRE>
			<A NAME="IRET">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
IRET
</FONT>
</TD>
<TD>No operands</TD>
<TD>

Interrupt Return.
<BR><BR>Algorithm:<BR><BR>
<FONT FACE="Fixedsys">
<UL>
	Pop from stack:
	<UL>
	<LI>IP</LI>
	<LI>CS</LI>
	<LI>flags register</LI>
	</UL>
</UL>
</FONT>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD COLSPAN=6><CENTER>popped</CENTER></TD> </TR>
</TABLE>
</FONT>

			<A NAME="JA">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
JA
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>label</NOBR>
</FONT>
</TD>
<TD>

Short Jump if first operand is Above second operand (as set by CMP instruction).
Unsigned.
<BR><BR>Algorithm:<BR><BR>
<FONT FACE="Fixedsys">
<UL>
	if (CF = 0) and (ZF = 0) then jump
</UL>
</FONT>
Example:<PRE><FONT FACE="Fixedsys">   include 'emu8086.inc'
   #make_COM#
   ORG 100h
   MOV AL, 250
   CMP AL, 5
   JA label1
   PRINT 'AL is not above 5'
   JMP exit
label1:
   PRINT 'AL is above 5'
exit:
   RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD COLSPAN=6>unchanged</TD> </TR>
</TABLE>
</FONT>

			<A NAME="JAE">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
JAE
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>label</NOBR>
</FONT>
</TD>
<TD>

Short Jump if first operand is Above or Equal to second operand (as set by CMP instruction).
Unsigned.
<BR><BR>Algorithm:<BR><BR>
<FONT FACE="Fixedsys">
<UL>
	if CF = 0 then jump
</UL>
</FONT>
Example:<PRE><FONT FACE="Fixedsys">   include 'emu8086.inc'
   #make_COM#
   ORG 100h
   MOV AL, 5
   CMP AL, 5
   JAE label1
   PRINT 'AL is not above or equal to 5'
   JMP exit
label1:
   PRINT 'AL is above or equal to 5'
exit:
   RET</FONT></PRE>

<FONT FACE="Fixedsys">
<TABLE BORDER=1 NOSHADE>
<TR> <TD>C</TD> <TD>Z</TD> <TD>S</TD> <TD>O</TD> <TD>P</TD> <TD>A</TD> </TR>
<TR> <TD COLSPAN=6>unchanged</TD> </TR>
</TABLE>
</FONT>

			<A NAME="JB">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
JB
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>label</NOBR>
</FONT>
</TD>
<TD>

Short Jump if first operand is Below second operand (as set by CMP instruction).
Unsigned.
<BR><BR>Algorithm:<BR><BR>
<FONT FACE="Fixedsys">
<UL>
	if CF = 1 then jump
</UL>
</FONT>
Example:<PRE><FONT FACE="Fixedsys">   include 'emu8086.inc'
   #make_COM#
   ORG 100h
   MOV AL, 1
   CMP AL, 5