i386/i386.reference/OUTS.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Opcode OUTS</TITLE>
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   7 <B>up:</B> <A HREF="c17.htm">
   8 Chapter 17 -- 80386 Instruction Set</A><BR>
   9 <B>prev:</B><A HREF="OUT.htm"> OUT Output to Port</A><BR>
  10 <B>next:</B><A HREF="POP.htm"> POP Pop a Word from the Stack</A>
  11 <P>
  12 <HR>
  13 <P>
  14 <H1>OUTS/OUTSB/OUTSW/OUTSD -- Output String to Port</H1>
  15
  16 <PRE>
  17 Opcode   Instruction     Clocks          Description
  18
  19 6E       OUTS DX,r/m8    14,pm=8*/28**   Output byte [(E)SI] to port in DX
  20 6F       OUTS DX,r/m16   14,pm=8*/28**   Output word [(E)SI] to port in DX
  21 6F       OUTS DX,r/m32   14,pm=8*/28**   Output dword [(E)SI] to port in DX
  22 6E       OUTSB           14,pm=8*/28**   Output byte DS:[(E)SI] to port in
  23                                          DX
  24 6F       OUTSW           14,pm=8*/28**   Output word DS:[(E)SI] to port in
  25                                          DX
  26 6F       OUTSD           14,pm=8*/28**   Output dword DS:[(E)SI] to port in
  27                                          DX
  28 </PRE>
  29
  30
  31 <EM>
  32 <H3>Notes</H3>
  33 <PRE>
  34    *If CPL <= IOPL
  35   **If CPL > IOPL or if in virtual 8086 mode
  36 </PRE>
  37 </EM>
  38
  39
  40 <H2>Operation</H2>
  41
  42 <PRE>
  43 IF AddressSize = 16
  44 THEN use SI for source-index;
  45 ELSE (* AddressSize = 32 *)
  46    use ESI for source-index;
  47 FI;
  48
  49 IF (PE = 1) AND ((VM = 1) OR (CPL > IOPL))
  50 THEN (* Virtual 8086 mode, or protected mode with CPL > IOPL *)
  51    IF NOT I-O-Permission (DEST, width(DEST))
  52    THEN #GP(0);
  53    FI;
  54 FI;
  55 IF byte type of instruction
  56 THEN
  57    [DX] := [source-index]; (* Write byte at DX I/O address *)
  58    IF DF = 0 THEN IncDec := 1 ELSE IncDec := -1; FI;
  59 FI;
  60 IF OperandSize = 16
  61 THEN
  62    [DX] := [source-index]; (* Write word at DX I/O address *)
  63    IF DF = 0 THEN IncDec := 2 ELSE IncDec := -2; FI;
  64 FI;
  65 IF OperandSize = 32
  66 THEN
  67    [DX] := [source-index]; (* Write dword at DX I/O address *)
  68    IF DF = 0 THEN IncDec := 4 ELSE IncDec := -4; FI;
  69    FI;
  70 FI;
  71 source-index := source-index + IncDec;
  72 </PRE>
  73
  74 <H2>Description</H2>
  75
  76 OUTS transfers data from the memory byte, word, or doubleword at the
  77 source-index register to the output port addressed by the DX register. If
  78 the address-size attribute for this instruction is 16 bits, SI is used for
  79 the source-index register; otherwise, the address-size attribute is 32 bits,
  80 and ESI is used for the source-index register.
  81 <P>
  82 OUTS does not allow specification of the port number as an immediate value.
  83 The port must be addressed through the DX register value. Load the correct
  84 value into DX before executing the OUTS instruction.
  85 <P>
  86 The address of the source data is determined by the contents of
  87 source-index register. Load the correct index value into SI or ESI before
  88 executing the OUTS instruction.
  89 <P>
  90 After the transfer, source-index register is advanced automatically. If
  91 the direction flag is 0 (<A HREF="CLD.htm">CLD</A>
  92 was executed), the source-index register is
  93 incremented; if the direction flag is 1 (<A HREF="STD.htm">STD</A> was executed), it is
  94 decremented. The amount of the increment or decrement is 1 if a byte is
  95 output, 2 if a word is output, or 4 if a doubleword is output.
  96 <P>
  97 OUTSB, OUTSW, and OUTSD are synonyms for the byte, word, and
  98 doubleword OUTS instructions. OUTS can be preceded by the
  99 <A HREF="REP.htm">REP</A>
 100 prefix for block output of CX bytes or words. Refer to the
 101 <A HREF="REP.htm">REP</A>
 102 instruction for details on this operation.
 103
 104 <H2>Flags Affected</H2>
 105
 106 None
 107
 108 <H2>Protected Mode Exceptions</H2>
 109
 110 #GP(0) if CPL is greater than IOPL and any of the corresponding I/O
 111 permission bits in TSS equals 1; #GP(0) for an illegal memory operand
 112 effective address in the CS, DS, or ES segments; #SS(0) for an illegal
 113 address in the SS segment; #PF(fault-code) for a page fault
 114
 115 <H2>Real Address Mode Exceptions</H2>
 116
 117 Interrupt 13 if any part of the operand would lie outside of the effective
 118 address space from 0 to 0FFFFH
 119
 120 <H2>Virtual 8086 Mode Exceptions</H2>
 121
 122 #GP(0) fault if any of the corresponding I/O permission bits in TSS
 123 equals 1; #PF(fault-code) for a page fault
 124
 125
 126 <P>
 127 <HR>
 128 <P>
 129 <B>up:</B> <A HREF="c17.htm">
 130 Chapter 17 -- 80386 Instruction Set</A><BR>
 131 <B>prev:</B><A HREF="OUT.htm"> OUT Output to Port</A><BR>
 132 <B>next:</B><A HREF="POP.htm"> POP Pop a Word from the Stack</A>
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