8086_instruction_set.html

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Load memory double word into word register and ES.
<BR><BR>Algorithm:<BR><BR>
<FONT FACE="Fixedsys">
<UL>
    <LI>REG = first word</LI>
	<LI>ES = second word</LI>
</UL>
</FONT>
<BR>
Example:
<PRE>
<FONT FACE="Fixedsys">
#make_COM#
ORG 100h

LES AX, m

RET

m  DW  1234h
   DW  5678h

END
</FONT>
</PRE>
AX is set to 1234h, ES is set to 5678h.

<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 COLSPAN=6>unchanged</TD> </TR>
</TABLE>
</FONT>


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




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

Load byte at DS:[SI] into AL. Update SI.<BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>AL = DS:[SI]<BR></LI>
<LI>if DF = 0 then
	<UL>
	<LI>SI = SI + 1</LI>
	</UL>
	else
	<UL>
	<LI>SI = SI - 1</LI>
	</UL>
</LI>
</UL>
</FONT>
Example:
<PRE>
<FONT FACE="Fixedsys">#make_COM#
ORG 100h

LEA SI, a1
MOV CX, 5
MOV AH, 0Eh

m: LODSB
INT 10h
LOOP m

RET

a1 DB 'H', 'e', 'l', 'l', 'o'</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="LODSW">&nbsp;</A>
</TD>
</TR>




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

Load word at DS:[SI] into AX. Update SI.<BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>AX = DS:[SI]<BR></LI>
<LI>if DF = 0 then
	<UL>
	<LI>SI = SI + 2</LI>
	</UL>
	else
	<UL>
	<LI>SI = SI - 2</LI>
	</UL>
</LI>
</UL>
</FONT>
Example:
<PRE>
<FONT FACE="Fixedsys">#make_COM#
ORG 100h

LEA SI, a1
MOV CX, 5

REP LODSW   ; finally there will be 555h in AX.

RET

a1 dw 111h, 222h, 333h, 444h, 555h</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="LOOP">&nbsp;</A>
</TD>
</TR>




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

Decrease CX, jump to label if CX not zero. <BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>CX = CX - 1<BR></LI>
<LI>if CX &lt;> 0 then
	<UL>
	<LI>jump</LI>
	</UL>
	else
	<UL>
	<LI>no jump, continue</LI>
	</UL>
</LI>
</UL>
</FONT>
Example:<PRE><FONT FACE="Fixedsys">   include 'emu8086.inc'
   #make_COM#
   ORG 100h
   MOV CX, 5
label1:
   PRINTN 'loop!'
   LOOP label1
   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="LOOPE">&nbsp;</A>
</TD>
</TR>




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

Decrease CX, jump to label if CX not zero and Equal (ZF = 1). <BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>CX = CX - 1<BR></LI>
<LI>if (CX &lt;> 0) and (ZF = 1) then
	<UL>
	<LI>jump</LI>
	</UL>
	else
	<UL>
	<LI>no jump, continue</LI>
	</UL>
</LI>
</UL>
</FONT>
Example:<PRE><FONT FACE="Fixedsys">; Loop until result fits into AL alone,
; or 5 times. The result will be over 255
; on third loop (100+100+100),
; so loop will exit.

   include 'emu8086.inc'
   #make_COM#
   ORG 100h
   MOV AX, 0
   MOV CX, 5
label1:
   PUTC '*'
   ADD AX, 100
   CMP AH, 0
   LOOPE label1
   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="LOOPNE">&nbsp;</A>
</TD>
</TR>




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

Decrease CX, jump to label if CX not zero and Not Equal (ZF = 0). <BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>CX = CX - 1<BR></LI>
<LI>if (CX &lt;> 0) and (ZF = 0) then
	<UL>
	<LI>jump</LI>
	</UL>
	else
	<UL>
	<LI>no jump, continue</LI>
	</UL>
</LI>
</UL>
</FONT>
Example:<PRE><FONT FACE="Fixedsys">; Loop until '7' is found,
; or 5 times.

   include 'emu8086.inc'
   #make_COM#
   ORG 100h
   MOV SI, 0
   MOV CX, 5
label1:
   PUTC '*'
   MOV AL, v1[SI]
   INC SI         ; next byte (SI=SI+1).
   CMP AL, 7
   LOOPNE label1
   RET
   v1 db 9, 8, 7, 6, 5</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="LOOPNZ">&nbsp;</A>
</TD>
</TR>




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

Decrease CX, jump to label if CX not zero and ZF = 0. <BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>CX = CX - 1<BR></LI>
<LI>if (CX &lt;> 0) and (ZF = 0) then
	<UL>
	<LI>jump</LI>
	</UL>
	else
	<UL>
	<LI>no jump, continue</LI>
	</UL>
</LI>
</UL>
</FONT>
Example:<PRE><FONT FACE="Fixedsys">; Loop until '7' is found,
; or 5 times.

   include 'emu8086.inc'
   #make_COM#
   ORG 100h
   MOV SI, 0
   MOV CX, 5
label1:
   PUTC '*'
   MOV AL, v1[SI]
   INC SI         ; next byte (SI=SI+1).
   CMP AL, 7
   LOOPNZ label1
   RET
   v1 db 9, 8, 7, 6, 5</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="LOOPZ">&nbsp;</A>
</TD>
</TR>




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

</TD>
<TD>

Decrease CX, jump to label if CX not zero and ZF = 1. <BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>CX = CX - 1<BR></LI>
<LI>if (CX &lt;> 0) and (ZF = 1) then
	<UL>
	<LI>jump</LI>
	</UL>
	else
	<UL>
	<LI>no jump, continue</LI>
	</UL>
</LI>
</UL>
</FONT>
Example:<PRE><FONT FACE="Fixedsys">; Loop until result fits into AL alone,
; or 5 times. The result will be over 255
; on third loop (100+100+100),
; so loop will exit.

   include 'emu8086.inc'
   #make_COM#
   ORG 100h
   MOV AX, 0
   MOV CX, 5
label1:
   PUTC '*'
   ADD AX, 100
   CMP AH, 0
   LOOPZ label1
   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="MOV">&nbsp;</A>
</TD>
</TR>




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

	SREG, memory<BR>
	memory, SREG<BR>
	REG, SREG<BR>
	SREG, REG
	</NOBR>
</FONT>
</TD>
<TD>

Copy operand2 to operand1.<BR><BR>
The MOV instruction <U>cannot</U>:
<UL>
<LI>set the value of the CS and IP registers.</LI>
<LI>copy value of one segment register to another segment register (should copy to general register first).</LI>
<LI>copy immediate value to segment register (should copy to general register first).</LI>
</UL>
<BR>Algorithm:<BR><BR>
<FONT FACE="Fixedsys">
<BLOCKQUOTE>
operand1 = operand2
</BLOCKQUOTE>
</FONT>
Example:<PRE><FONT FACE="Fixedsys">#make_COM#
ORG 100h
MOV AX, 0B800h    ; set AX = B800h (VGA memory).
MOV DS, AX        ; copy value of AX to DS.
MOV CL, 'A'       ; CL = 41h (ASCII code).
MOV CH, 01011111b ; CL = color attribute.
MOV BX, 15Eh      ; BX = position on screen.
MOV [BX], CX      ; w.[0B800h:015Eh] = CX.
RET               ; returns to operating system.
</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="MOVSB">&nbsp;</A>
</TD>
</TR>




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

Copy byte at DS:[SI] to ES:[DI].
Update SI and DI.<BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>ES:[DI] = DS:[SI]<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:<PRE><FONT FACE="Fixedsys">#make_COM#
ORG 100h

LEA SI, a1
LEA DI, a2
MOV CX, 5
REP MOVSB

RET

a1 DB 1,2,3,4,5
a2 DB 5 DUP(0)</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="MOVSW">&nbsp;</A>
</TD>
</TR>




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

Copy <b>word</b> at DS:[SI] to ES:[DI].
Update SI and DI.<BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>ES:[DI] = DS:[SI]<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:<PRE><FONT FACE="Fixedsys">#make_COM#
ORG 100h

LEA SI, a1
LEA DI, a2
MOV CX, 5
REP MOVSW

RET

a1 DW 1,2,3,4,5
a2 DW 5 DUP(0)</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="MUL">&nbsp;</A>
</TD>
</TR>




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

Unsigned 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, 200   ; AL = 0C8h
MOV BL, 4
MUL BL        ; AX = 0320h (800)
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 high section of the result is zero.
</FONT>

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




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

Negate. Makes operand negative (two's complement).
<BR><BR>Algorithm:<BR><BR>
 <FONT FACE="Fixedsys">
 <UL>
 <LI>Invert all bits of the operand</LI>
 <LI>Add 1 to inverted operand</LI>
 </UL>
 </FONT>
    Example:<PRE><FONT FACE="Fixedsys">MOV AL, 5   ; AL = 05h
NEG AL      ; AL = 0FBh (-5)
NEG AL      ; AL = 05h (5)
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="NOP">&nbsp;</A>
</TD>
</TR>




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

No Operation.<BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>Do nothing<BR></LI>
</UL>
</FONT>
    Example:<PRE><FONT FACE="Fixedsys">; do nothing, 3 times:
NOP
NOP
NOP
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="NOT">&nbsp;</A>
</TD>
</TR>




<TR>
<TD>
<FONT FACE="Fixedsys">
NOT
</FONT>
</TD>
<TD>
<FONT FACE="Fixedsys">
	<NOBR>
	REG<BR>
	memory<BR>
	</NOBR>
</FONT>
</TD>
<TD>

Invert each bit of the operand.<BR><BR>Algorithm:
<BR><BR>
<FONT FACE="Fixedsys">
<UL>
<LI>if bit is 1 turn it to 0.<BR></LI>
<LI>if bit is 0 turn it to 1.<BR></LI>
</UL>
</FONT>
    Example:<PRE><FONT FACE="Fixedsys">MOV AL, 00011011b
NOT AL   ; AL = 11100100b
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="OR">&nbsp;</A>
</TD>
</TR>



<TR>
<TD>
<FONT FACE="Fixedsys">
OR
</FONT>
</TD>
<TD>
<FONT FACE="