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Equivalence !

Posted on 1999-01-13
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Last Modified: 2010-04-02
What's the equivalent of the function 'outportb' (Borland C++ 3.1 [DOS]) in Microsoft Visual C++ 5.0 [WINDOWS] ?
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Question by:mike_marquet
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by:jkr
ID: 1182048
You cannot access the hardware directly on 32bit Windows platforms, so there simply is _no_ equivalent for this function - sorry that the answer is so negative, but i all i can do is to point you to the Win9x/NT DDKs (Device Driver Kits)...
Why do you need to use 'outportb()'? Maybe we can find a way to get around this...
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by:viktornet
ID: 1182049
you could use assembler to send stuff to the ports....

asm {
  mov al, 5
  mov dl, 2h
  out dl, al
}

which would write the value 5 to port 2...

-Viktor
--Ivanov
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Author Comment

by:mike_marquet
ID: 1182050
I want to access an I/O card with 8255 chips.
Can I use assembler in a window program ?
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Expert Comment

by:koskia
ID: 1182051
ofcourse you can use assembler,
but you must take in consideration that window handles the ports. and some other applications may also try to do the same,
in a multithreaded environment you're taking a big risk
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Author Comment

by:mike_marquet
ID: 1182052
Thanks. I will try it.

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by:jkr
ID: 1182053
You may of course reject the answer, but this does _NOT_ affect the fact that it is true...
asm {
  mov al, 5
  mov dl, 2h
  out dl, al
}
-> EXCEPTION_PRIV_INSTRUCTION ;-)
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Accepted Solution

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jrmcg earned 60 total points
ID: 1182054
To read and write to a port say COM 1 use this --
#include <conio.h>

UINT Port = 1016 // 3F8
int    Data = 2;
int    ReturnData;
// Write
_outp(Port, Data);

// Read
ReturnData = _inp(Port);

This is what I use.  Again you need to keep in mind that windows can still use those ports,  if you are writing to your own card just use the address of that port.  As long as you haven't installed other software that is accessing that card for one reason or another you shouldn't have any problems.

Let me know if you need further help with it..

J.R.
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by:viktornet
ID: 1182055
jkr, I just tried to give something like a pseudo code and say that the individual could use Assembler.. that's all.. I've never said that the code I wrote will work just the way it is... :))

-Viktor
--Ivanov
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Expert Comment

by:jkr
ID: 1182056
Viktor, i agree - you can always use assembler, but certain instructions are restricted to ring 0 (i.e. kernel mode)...
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Author Comment

by:mike_marquet
ID: 1182057
To JKR,

How can I set the privilege on NT to use inp(...) ?

I have try this but it doesn't work !

  BOOL             rcCode;
  HANDLE           hToken;
  TOKEN_PRIVILEGES tkp;

  rcCode = OpenProcessToken(GetCurrentProcess(),TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY,&hToken);
  if (rcCode == FALSE) return FALSE;

  LookupPrivilegeValue(NULL, SE_SECURITY_NAME, &tkp.Privileges[0].Luid);

  tkp.PrivilegeCount = 1; // One privileges to set
  tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;

  AdjustTokenPrivileges(hToken, FALSE, &tkp, 0, (PTOKEN_PRIVILEGES)NULL, 0);

  if (GetLastError() != ERROR_SUCCESS) return FALSE;

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Expert Comment

by:jkr
ID: 1182058
You cannot - privileged instructions only work in ring0 (i.e. kernel mode), as i stated in my answer which you have chosen to reject ;-)
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