Re: Signed, Unsigned syntax issues. Please help, I'm stumped

On Jun 12, 2:42 pm, Jim Lewis <j...@[EMAIL PROTECTED]
> wrote:
> rickman
>
>
>
> > BTW, here is one of the reasons I am getting tried of using VHDL.  I
> > have coded FPGAs in VHDL off and on for some 10 years.  Every time I
> > start a new design (sometimes as long as 18 months since the last one)
> > I have to pick up all of my books again to remember the details and to
> > read my notes on the various shortcuts to efficient use.  I typically
> > find that the shortcuts are not very short and look for new ones.  The
> > notation is just so verbose for simple things.  Here is an example.
>
> > CTPBitCnt is an unsigned.
>
> > What I mean...
> >   CTPBitCnt <= 1;
>
> > What I have to write...
> >   CTPBitCnt <= to_unsigned(1, CTPBitCnt'length);
>
> > Doesn't that seem a bit wordy?  I guess this example goes back to the
> > inability to overload the assignment operator which someone has
> > indicated may be changed in the next revision of the language.
>
> Jonathan just submitted a language feature request WRT to overloading
> assignment, however, the standard is already at the balloting point so
> it will not make the 2008 revision.
>
> What has been added is a decimal notation for bit string literals
> and a sizing indication.
>
> signal CTPBitCnt : unsigned (14 downto 0) ; -- 15 bits
> . . .
> -- Representing 1 as a 15 bit object in either hex or decimal
>
> CTPBitCnt <= 15D"1" ;   -- Decimal notation
> CTPBitCnt <= 15X"1" ;   -- Hex notation
>
> BTW, these are also in Accellera standard VHDL-2006-rev3.0, so
> if your vendors were looking out for your interests, they would
> have already should implemented these.
>
> Make sure to submit these as bug/enhancement requests.  This is
im****tant
> as this is what lets them know the VHDL community wants the new
features.
>
> Best,
> Jim
>
> P.S.  Did you grab the paper I referenced:
>    http://www.synthworks.com/papers/vhdl_math_tricks_mapld_2003.pdf

Oh, BTW, some of the features you list above are not really a great
solution.  If I write...

CTPBitCnt <= 15D"1" ;   -- Decimal notation

I am sprinkling my code with numerical constants that have to be
changed, one at a time, if my declaration changes.  What exactly is
the problem that is solved by not allowing...

CTPBitCnt <= 1;

Isn't the meaning of this very clear?  If I am assigning it to a
signed signal, then it should be treated as signed, right?  If I am
assigning it to an unsigned signal, then it should be treated as
unsigned, right?  Maybe I do have a problem with strong typing if it
requires me to be so verbose that the size of my files triple without
adding anything to the clarity of the code.

CTPBitCnt <= to_unsigned(1, CTPBitCnt'length);

What am I missing?

Rick