Case statement syntax

Not sure the best way to do this. Using Xilinx ISE 7.1. This is all in a
"clocked" if statement.

I was intending to use a case statement where there might be some "don't
care" bits in the "when" range.

case expression(2 downto 0)
when "0xx"
perform this
when "100"
perform that
etc

How can I concatenate a number of when expressions.

case expression(2 downto 0)
when "000"
perform this
when "001"
perform that
when "010"
perform this
when "011"
perform that

etc

Where "perform this" may be a long series of expressions.

Is there a better way of doing it?

Fred

Fred,
Use a '|' to separate case choices.
For your first example:

case expr(2 downto 0) is
when "000" | "001" | "010" | "011" =>
> perform this
> when "100" =>
> perform that

In VHDL-2006 there is a _proposal_ for a case statement
with a don't care, however, that will not do you any good
on the short term.

Cheers,
Jim


> I was intending to use a case statement where there might be some "don't
> care" bits in the "when" range.
>
> case expression(2 downto 0)
> when "0xx"
> perform this
> when "100"
> perform that
> etc
>

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~
Jim Lewis
Director of Training private.php?do=newpm&u=
SynthWorks Design Inc. http://www.SynthWorks.com
1-503-590-4787

Expert VHDL Training for Hardware Design and Verification
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~

Jim Lewis

"Jim Lewis" <> wrote in message
news:...
> Fred,
> Use a '|' to separate case choices.
> For your first example:
>
> case expr(2 downto 0) is
> when "000" | "001" | "010" | "011" =>
> > perform this
> > when "100" =>
> > perform that
>
> In VHDL-2006 there is a _proposal_ for a case statement
> with a don't care, however, that will not do you any good
> on the short term.
>
> Cheers,
> Jim
>
>
>> I was intending to use a case statement where there might be some "don't
>> care" bits in the "when" range.
>>
>> case expression(2 downto 0)
>> when "0xx"
>> perform this
>> when "100"
>> perform that
>> etc
>>
>

Bit late I know but - many thanks.

Fred