Read/Write Parallel Port In Assembly Language

[joeyc100]

Hi all,
I would like to read and write the parallel port (0378h) in assembly language.
I am aware of an Inpout32.dll and have installed it in SYSTEM32\DRIVERS, but I do not know the calling sequence. Can anyone help.
Joe.

 

[samuria]

Why do you need a dll for assembly language?

 

[joeyc100]

Because Win 7 does not allow access to the parallel port. Just doing an "OUT 0378h,reg" from an assembly language subroutine called by a high level program results in a NOP. The system level driver INPOUT32.sys was developed for this reason, but is used by C programs.

 

[LMiller7]

I located this with a search:
Download Highrez InpOut32/InpOut64 bit Hardware Port Driver 1.5.0.0 for Windows ME, Windows 2K, Windows XP, Windows 2003, Windows XP 64 bit

I have not used the dll and cannot help you with it.

 

[joeyc100]

Thanks, but this is the item that I mentioned: Inpout32. It can be installed in the system32\drivers file, or included in the user's program file, or as a .lib file for C programs. But I do not know how to access it from an assembly language subroutine: the calling sequence with the passing of arguments. It appears obvious that a C program once compiled into machine language does this.

 

[iko22]

Hi all,
I would like to read and write the parallel port (0378h) in assembly language.

Because Win 7 does not allow access to the parallel port. Just doing an "OUT 0378h,reg" from an assembly language subroutine called by a high level program results in a NOP.

You could try installing DOSbox, and running your assembly language program from within DOSbox. That way you wont need InpOut32 and you will safely bypass the Protect Mode features of the Windows Operating System.

Source: MASM using DOSBOX in Windows 10/8/7

 

[joeyc100]

Dosbox does not handle the parallel port except with an add-on and then only as a passthru for a printer. I have tried it. I need bidirectional.

 

[Alejandro85]

So your concrete problem is how to call a C function exported from an external dll from assembly code?

 

[joeyc100]

Yes. And, further, how to do it in assembly language.

 

[Alejandro85]

You'll need to know the calling convention (ABI) that the library uses to communicate, most likely it's cdecl for C-written programs, or stdcall for WinApi style. Then have a look at the relevant documentation for the exact instructions to call the API. A source I like on the topic is Wikipedia which explains the differences between them.
It's pretty much similar to how you call the Windows API standard functions from assembly.

 

[joeyc100]

Thank you. I will look into them.