Difference between revisions of "Assembler:Commands:IN"

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(Created page with 'Category:Assembler '''command''' in ''destination'', ''source'' Input from Port. Copies the value from the I/O port specified with the second operand (source operand) to the…')
 
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At the machine code level, I/O instructions are shorter when accessing 8-bit I/O ports. Here, the upper eight bits of the port address will be 0.
 
At the machine code level, I/O instructions are shorter when accessing 8-bit I/O ports. Here, the upper eight bits of the port address will be 0.
  
This instruction is only useful for accessing I/O ports located in the processor's I/O address space. See Chapter 13, Input/Output, in the IA-32 Intel Architecture Software Developer's Manual, Volume 1, for more information on accessing I/O ports in the I/O address space.
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This instruction is only useful for accessing I/O ports located in the processor's I/O address space.
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For more information on accessing I/O ports in the I/O address space, see: [https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-vol-1-manual.pdf 64-ia-32-architectures-software-developer-vol-1-manual.pdf]
  
 
[http://c9x.me/x86/html/file_module_x86_id_139.html c9x.me/x86/html/file_module_x86_id_139.html]
 
[http://c9x.me/x86/html/file_module_x86_id_139.html c9x.me/x86/html/file_module_x86_id_139.html]

Latest revision as of 22:55, 24 January 2018

command in destination, source

Input from Port. Copies the value from the I/O port specified with the second operand (source operand) to the destination operand (first operand).


Copies the value from the I/O port specified with the second operand (source operand) to the destination operand (first operand). The source operand can be a byte-immediate or the DX register; the destination operand can be register AL, AX, or EAX, depending on the size of the port being accessed (8, 16, or 32 bits, respectively). Using the DX register as a source operand allows I/O port addresses from 0 to 65,535 to be accessed; using a byte immediate allows I/O port addresses 0 to 255 to be accessed.

When accessing an 8-bit I/O port, the opcode determines the port size; when accessing a 16- and 32-bit I/O port, the operand-size attribute determines the port size.

At the machine code level, I/O instructions are shorter when accessing 8-bit I/O ports. Here, the upper eight bits of the port address will be 0.

This instruction is only useful for accessing I/O ports located in the processor's I/O address space.

For more information on accessing I/O ports in the I/O address space, see: 64-ia-32-architectures-software-developer-vol-1-manual.pdf

c9x.me/x86/html/file_module_x86_id_139.html


Command Parameters[edit]

Parameter Description
destination The destination of the byte(s) read
source The I/O port number to read


See also[edit]

External links[edit]