i386/i386.reference/INS.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Opcode INS</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="INC.htm"> INC Increment by 1</A><BR>
  10 <B>next:</B><A HREF="INT.htm"> INT/INTO Call to Interrupt Procedure</A>
  11 <P>
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  13 <P>
  14 <H1>INS/INSB/INSW/INSD -- Input from Port to String</H1>
  15
  16 <PRE>
  17 Opcode  Instruction    Clocks         Description
  18
  19 6C      INS r/m8,DX    15,pm=9*/29**  Input byte from port DX into ES:(E)DI
  20 6D      INS r/m16,DX   15,pm=9*/29**  Input word from port DX into ES:(E)DI
  21 6D      INS r/m32,DX   15,pm=9*/29**  Input dword from port DX into ES:(E)DI
  22 6C      INSB           15,pm=9*/29**  Input byte from port DX into ES:(E)DI
  23 6D      INSW           15,pm=9*/29**  Input word from port DX into ES:(E)DI
  24 6D      INSD           15,pm=9*/29**  Input dword from port DX into ES:(E)DI
  25 </PRE>
  26
  27 <EM>
  28 <H3>Notes</H3>
  29 <PRE>
  30    *If CPL <= IOPL
  31   **If CPL > IOPL or if in virtual 8086 mode
  32 </PRE>
  33 </EM>
  34
  35 <H2>Operation</H2>
  36
  37 <PRE>
  38 IF AddressSize = 16
  39 THEN use DI for dest-index;
  40 ELSE (* AddressSize = 32 *)
  41    use EDI for dest-index;
  42 FI;
  43 IF (PE = 1) AND ((VM = 1) OR (CPL > IOPL))
  44 THEN (* Virtual 8086 mode, or protected mode with CPL > IOPL *)
  45    IF NOT I-O-Permission (SRC, width(SRC))
  46    THEN #GP(0);
  47    FI;
  48 FI;
  49 IF byte type of instruction
  50 THEN
  51    ES:[dest-index] := [DX]; (* Reads byte at DX from I/O address space *)
  52    IF DF = 0 THEN IncDec := 1 ELSE IncDec := -1; FI;
  53 FI;
  54 IF OperandSize = 16
  55 THEN
  56    ES:[dest-index] := [DX]; (* Reads word at DX from I/O address space *)
  57    IF DF = 0 THEN IncDec := 2 ELSE IncDec := -2; FI;
  58 FI;
  59 IF OperandSize = 32
  60 THEN
  61    ES:[dest-index] := [DX]; (* Reads dword at DX from I/O address space *)
  62    IF DF = 0 THEN IncDec := 4 ELSE IncDec := -4; FI;
  63 FI;
  64 dest-index := dest-index + IncDec;
  65 </PRE>
  66
  67 <H2>Description</H2>
  68
  69 INS transfers data from the input port numbered by the DX register to
  70 the memory byte or word at ES:dest-index. The memory operand must
  71 be addressable from ES; no segment override is possible. The destination
  72 register is DI if the address-size attribute of the instruction is 16 bits,
  73 or EDI if the address-size attribute is 32 bits.
  74 <P>
  75 INS does not allow the specification of the port number as an immediate
  76 value. The port must be addressed through the DX register value. Load
  77 the correct value into DX before executing the INS instruction.
  78 <P>
  79 The destination address is determined by the contents of the destination
  80 index register. Load the correct index into the destination index register
  81 before executing INS.
  82 <P>
  83 After the transfer is made, DI or EDI advances automatically. If the
  84 direction flag is 0 (CLD was executed), DI or EDI increments; if the
  85 direction flag is 1 (STD was executed), DI or EDI decrements. DI
  86 increments or decrements by 1 if a byte is input, by 2 if a word is input,
  87 or by 4 if a doubleword is input.
  88 <P>
  89 INSB, INSW and INSD are synonyms of the byte, word, and doubleword
  90 INS instructions. INS can be preceded by the
  91 <A HREF="REP.htm">REP</A> prefix for block input of
  92 CX bytes or words. Refer to the
  93 <A HREF="REP.htm">REP</A> instruction for details of this
  94 operation.
  95
  96 <H2>Flags Affected</H2>
  97
  98 None
  99
 100 <H2>Protected Mode Exceptions</H2>
 101
 102 #GP(0) if CPL is numerically greater than IOPL and any of the
 103 corresponding I/O permission bits in TSS equals 1; #GP(0) if the
 104 destination is in a nonwritable segment; #GP(0) for an illegal memory
 105 operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for
 106 an illegal address in the SS segment; #PF(fault-code) for a page fault
 107
 108 <H2>Real Address Mode Exceptions</H2>
 109
 110 Interrupt 13 if any part of the operand would lie outside of the effective
 111 address space from 0 to 0FFFFH
 112
 113 <H2>Virtual 8086 Mode Exceptions</H2>
 114
 115 #GP(0) fault if any of the corresponding I/O permission bits in TSS
 116 equals 1; #PF(fault-code) for a page fault
 117
 118
 119 <P>
 120 <HR>
 121 <P>
 122 <B>up:</B> <A HREF="c17.htm">
 123 Chapter 17 -- 80386 Instruction Set</A><BR>
 124 <B>prev:</B><A HREF="INC.htm"> INC Increment by 1</A><BR>
 125 <B>next:</B><A HREF="INT.htm"> INT/INTO Call to Interrupt Procedure</A>
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