Low Level IO

Low Level IO

[JOSE VICENTE]

Does anyone know how can I read/write the parallel port using Linux and Gnat
3.10 ?
I've been trying things like this and 'Storage Error' or 'Program Error'
raises.
    ......
    type Byte is mod 2**8;
    for Byte'Size use 8;
    Parallel_Port:Byte;
    for Parallel_Port'Address use
System.Storage_Elements.To_Address(16#3BC#);
    ......
    begin
    ......
    Parallel_Port:=value;    -- The exception raises at this point.
    ......
Thanks in advance.

Re: Low Level IO

[Samuel Tardieu]

>>>>> "Jose" == JOSE VICENTE <319089@cepsz.unizar.es> writes:

Jose> Does anyone know how can I read/write the parallel port using
Jose> Linux and Gnat 3.10 ?

It has nothing to do with GNAT. If you try the same thing in C with

   main() { *(char *)0x3bc = 0; }

you will get a segmentation fault.

When you are using a real OS (such as Linux), you have to ask the OS
to give you certain permissions (on Linux, look at ioperm() and iopl()).

Moreover, the memory space you see has nothing to do with the physical 
memory, that means that 16#3bc# doesn't point onto the parallel port.

  Sam
-- 
Samuel Tardieu -- sam@ada.eu.org

Re: Low Level IO

[JOSE VICENTE]

Thanks , I see I must review my OS notes first.

Re: Low Level IO

[Tarjei Tj�stheim Jensen]

JOSE VICENTE wrote :
>Does anyone know how can I read/write the parallel port using Linux and Gnat
>3.10 ?
>I've been trying things like this and 'Storage Error' or 'Program Error'
>raises.
>    ......
>    type Byte is mod 2**8;
>    for Byte'Size use 8;
>    Parallel_Port:Byte;
>    for Parallel_Port'Address use
>System.Storage_Elements.To_Address(16#3BC#);
>    ......
>    begin
>    ......
>    Parallel_Port:=value;    -- The exception raises at this point.


I believe that you are trying to write into the BIOS area.

To my knowledge the paralell port lives in I/O space. I/O space is different
from program/data space. You should use something similar to the port()
function which many C compilers have. It may very well be that this can be done
using assembly language insertion. Robert Dewar can probably tell you the
preferred method.

It may well be that this is documentet in the GNAT documentation. Please have a
go at looking it up there first.

Greetings,