How to overide ieee.std_logic_1164.all

The thing is I want to include the ieee.std_logic_1164.all library in
the project but i want to redefine the XOR by mine.(I want to override
XOR so that it will have a delay).How should i do that?
I can not use a custom made component and map all the current XOR to
it.Also my experience with VHDL is limited so any advice will be more
than welcome!

Nikos

Nikos wrote:
> The thing is I want to include the ieee.std_logic_1164.all library in
> the project but i want to redefine the XOR by mine.(I want to override
> XOR so that it will have a delay).How should i do that?
> I can not use a custom made component and map all the current XOR to
> it.Also my experience with VHDL is limited so any advice will be more
> than welcome!
>
Functions cannot have a delay. Sorry.

So if you want a delay and you don't want to write something
like:

Y <= A xor B after 10 ns ;

and you want to use a subprogram, then you must write a
procedure (a subprogram that can have a delay), however,
note that a procedure is a statement, so the output is
part of the call:

XOR_DELAYED (Y, A, B) ;

You can find the syntax for a procedure in any book or maybe the
FAQ which can be found at: http://www.vhdl.org

Good Luck,
Jim
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~
Jim Lewis
Director of Training private.php?do=newpm&u=
SynthWorks Design Inc. http://www.SynthWorks.com
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Expert VHDL Training for Hardware Design and Verification
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~

Jim Lewis

Jim Lewis wrote:
> Nikos wrote:
>> The thing is I want to include the ieee.std_logic_1164.all library in
>> the project but i want to redefine the XOR by mine.(I want to override
>> XOR so that it will have a delay).How should i do that?
>> I can not use a custom made component and map all the current XOR to
>> it.Also my experience with VHDL is limited so any advice will be more
>> than welcome!
>>
> Functions cannot have a delay. Sorry.
I didn't mention functions somewhere?Did I?

> So if you want a delay and you don't want to write something
> like:
>
> Y <= A xor B after 10 ns ;
>
> and you want to use a subprogram, then you must write a
> procedure (a subprogram that can have a delay), however,
> note that a procedure is a statement, so the output is
> part of the call:
>
> XOR_DELAYED (Y, A, B) ;
>
Actually I want only to override the xor of the ieee.That would
suffice.If I try to have something like a component XOR_DELAYED() then
that would mean a huge change of code that is not possible.The same
applies to adding: "after 10 ns".

The question is: is there a way to OVERRIDE XOR?I don't want to overload
(in software engineering terms) the XOR.



> You can find the syntax for a procedure in any book or maybe the
> FAQ which can be found at: http://www.vhdl.org
>
> Good Luck,
> Jim

Thanks

Nikos

Nikos wrote:

> I didn't mention functions somewhere? Did I?

You mentioned ieee.std_logic_1164.xor

Let's have a look:

FUNCTION "xor" ( l : std_ulogic; r : std_ulogic ) RETURN UX01;

Looks like a function to me.

> Actually I want only to override the xor of the ieee.That would
> suffice.If I try to have something like a component XOR_DELAYED() then
> that would mean a huge change of code that is not possible.

When I overload a function, there is no change to the code.
It just refines what the existing function calls will do.

> The question is: is there a way to OVERRIDE XOR?I don't want to overload
> (in software engineering terms) the XOR.

No.

-- Mike Treseler

Mike Treseler

Mike Treseler wrote:
> Nikos wrote:
>
>> I didn't mention functions somewhere? Did I?
>
> You mentioned ieee.std_logic_1164.xor
>
> Let's have a look:
>
> FUNCTION "xor" ( l : std_ulogic; r : std_ulogic ) RETURN UX01;
>
> Looks like a function to me.
>
Didn't know that there was a function behind...Actually I was hoping
that it wasn't one.


>> Actually I want only to override the xor of the ieee.That would
>> suffice.If I try to have something like a component XOR_DELAYED() then
>> that would mean a huge change of code that is not possible.
>
> When I overload a function, there is no change to the code.
> It just refines what the existing function calls will do.
>
>> The question is: is there a way to OVERRIDE XOR?I don't want to
>> overload (in software engineering terms) the XOR.
>
> No.
>
Bad

> -- Mike Treseler

Thank you!
Nikos

Nikos

>>
>>> The question is: is there a way to OVERRIDE XOR?I don't want to overload
>>> (in software engineering terms) the XOR.
>>
>> No.
>>
> Bad
>

Perhaps back up a step and explain what the real problem is that adding a
delay to xor would solve. That might suggest a better approach to the real
problem.

KJ

KJ