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Q72706: DOCERR: Encoding for LTR Instruction Is Incorrect

Article: Q72706
Product(s): Microsoft Macro Assembler
Version(s): 5.1,5.1a,6.0,6.0a,6.0b
Operating System(s): 
Keyword(s): 
Last Modified: 06-MAY-2001

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The information in this article applies to:

- Microsoft Macro Assembler (MASM), versions 5.1, 5.1a, 6.0, 6.0a, 6.0b 
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SUMMARY
=======

The LTR (load task register) instruction is documented incorrectly in the
printed documentation for the Microsoft Macro Assembler (MASM) versions 5.1, and
5.1a and the online help for MASM versions 6.0, 6.0a, and 6.0b. The following is
the documented encoding:

  00001111 00000000 mod,001,r/m

However, this is the actual encoding for LTR:

  00001111 00000000 mod,011,r/m

MORE INFORMATION
================

If the sample code below is assembled and a source listing is generated, the
following encoding is listed:

  0000  0F 00 DB              ltr BX
  0003  0F 00 1D 00000000 R   ltr task

0DBh evaluates to 11011011y, 1Dh evaluates to 00011101y.

Sample Code
-----------

  ; Assemble Options Needed: /c /Fl

  .386p
  .MODEL small
  .STACK 4096

  .DATA
  task dw ?

  .CODE
  main PROC
     ltr BX
     ltr task
  main ENDP
  END

Additional query words: 5.10 5.10a 6.00 6.00a 6.00b

======================================================================
Keywords          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM510 kbMASM600 kbMASM600a kbMASM510a kbMASM600b
Version           : :5.1,5.1a,6.0,6.0a,6.0b

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