undeclared loop variable

It seems that I can drop this into a testbench without
declaring col as a signal or a variable or anything.
What is vhdl doing with col?

for col in 1 to 16 loop
wait for clkperiod;
end loop;

Brad Smallridge

"Brad Smallridge" <> writes:

> It seems that I can drop this into a testbench without
> declaring col as a signal or a variable or anything.
> What is vhdl doing with col?

VHDL considers the iteration variable to be constant for each pass
through the loop.

Regards,


Kai
--
Kai Harrekilde-Petersen <khp(at)harrekilde(dot)dk>

Kai Harrekilde-Petersen

Brad Smallridge wrote:

> It seems that I can drop this into a testbench without
> declaring col as a signal or a variable or anything.
> What is vhdl doing with col?
>
> for col in 1 to 16 loop
> wait for clkperiod;
> end loop;
>
>


the only potential draw back that I see to this type of a construct is
that you can't reference "col" anywhere outside of the loop

My Name

The looping index is considered an implicit variable in vhdl and is
local to the for loop.

Neo

Neo wrote:
> The looping index is considered an implicit variable in vhdl and is
> local to the for loop.
>

In fact as Kai pointed out, the loop index is a constant.

All that means in practice is that you can't, for instance, do

col := 10;

inside the loop.

regards
Alan

--

Alan Fitch
Doulos Ltd
http://www.doulos.com

Alan Fitch

My Name wrote:
>
>> for col in 1 to 16 loop
>> wait for clkperiod;
>> end loop;
>
> the only potential draw back that I see to this type of a construct is
> that you can't reference "col" anywhere outside of the loop

I don't see that as a drawback. What value would you expect "col" to
have outside the loop anyway?

Paul.

Paul Uiterlinden

On Thu, 24 Mar 2005 00:30:14 -0700, My Name <> wrote:

[VHDL 'for' loop index is an implied constant within the loop...]
>the only potential draw back that I see to this type of a construct is
>that you can't reference "col" anywhere outside of the loop

Can you show me an example of this kind of thing that I could
read and yet still retain my lunch?
--
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Jonathan Bromley

Paul Uiterlinden wrote:
> My Name wrote:
>
>>
>>> for col in 1 to 16 loop
>>> wait for clkperiod;
>>> end loop;
>>
>>
>> the only potential draw back that I see to this type of a construct is
>> that you can't reference "col" anywhere outside of the loop
>
>
> I don't see that as a drawback. What value would you expect "col" to
> have outside the loop anyway?
>
> Paul.


well, neither do I really.

Michael