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About process

 
 
mallu
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      07-05-2006

Hi, all

I am newer to VHDL. I have a small design problem.
I have two clocks and each one activate different process statements. I
declared one variable in one process statement. But as per my design it
should also modify in another process statement. To be clear How can i
modify one variable or signal in two process statements.

 
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KJ
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      07-05-2006
mallu wrote:
> Hi, all
>
> I am newer to VHDL. I have a small design problem.
> I have two clocks and each one activate different process statements. I
> declared one variable in one process statement. But as per my design it
> should also modify in another process statement. To be clear How can i
> modify one variable or signal in two process statements.


Use a shared variable if it needs to be a variable, signals can be
assigned within two processes.

I'm betting that there's more that you'll find that you really need to
figure out first before you can sucessfully do either approach, but
based on the info you posted this is the answer.

KJ

 
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Ralf Hildebrandt
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      07-05-2006
mallu wrote:


> I am newer to VHDL. I have a small design problem.
> I have two clocks and each one activate different process statements. I
> declared one variable in one process statement. But as per my design it
> should also modify in another process statement. To be clear How can i
> modify one variable or signal in two process statements.



Simple answer: Don't do it if you want to write synthesizable code.

You have to model some signal that is driven by the 2nd process and
evaluated in the 1st one. This signal should show, that the variable has
to be modified now.

Think in terms of hardware. The state of one flipflop cannot be changed
from two different and _independent_ drivers. You have to model some
kind of handshaking. Maybe if the 2nd process sets an enable-signal
active, then the flipflop of the 1st process has to sample a signal
provided by the 2nd process, while otherwise it would sample a different
signal.

If you are really sure, that there is no way to model it this way a
pseudo dual-edge flipflop may be an option. But I strongly recommend to
think about a "normal" synchronous solution.


Ralf
 
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john
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      07-05-2006
Hi,
Simplify your design as much as possible. Try to use only master clock.
What are you trying to do ( application)?
John
mallu wrote:
> Hi, all
>
> I am newer to VHDL. I have a small design problem.
> I have two clocks and each one activate different process statements. I
> declared one variable in one process statement. But as per my design it
> should also modify in another process statement. To be clear How can i
> modify one variable or signal in two process statements.


 
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