Re: [vhdl-200x-ft] VHDL Fixed-Point Comment

It seems to be using a howitzer when a pea-shooter will do to introduce 
a new language element (an attribute) when a function will do the job.  
Is there is some aspect to this that I am not getting such that an 
attribute provides capability that a function would not?  If not, 
perhaps a function added to fixed point packages for this is most 
appropriate.

Karl

Scott D. Hoy wrote:

> Hi,
>
>  
>
> I am wondering with the VHDL fixed-point package would it benefit 
> anyone if two new attributes 'ilength and 'flength could be added to 
> the LRM or is there is a way for the designer to define 'ilength and 
> 'flength in a custom user defined package. 'ilength would return a 
> natural that would be the number of integer bits and 'flength also 
> would return a natural that would be the number of fractional bits. 
> For obtaining the number of integer bits 'ilength would be a constant 
> method for both the sfixed and ufixed types.  Currently to obtain the 
> number of integer bits the 'high returns the correct number for sfixed 
> but for ufixed a 'high+1 needs to be done to obtain the correct 
> number.  The 'ilength would clean up the users code by removing 
> 'high+1 or 'high with a common attribute that would return the correct 
> number based on the data type sfixed or ufixed.  For consistency and 
> to keep vector lengths positive, the 'flength would return the number 
> of fractional bits without having to do abs(fp'low).  This could clean 
> up the resulting code and make it easier to read within a design team.
>
>  
>
> I have started building a fixed-point library to help speed up 
> translation of the Mathworks Simulink Fixed-Point Models to VHDL and 
> having the ability to call a 'ilength or 'flength would come in handy 
> on building very generic synthesizable VHDL fixed-point library(being 
> able to have fully generic arrays and records (i.e. a vector/matrix of 
> sfixed and/or ufixed and complex sfixed and a complex ufixed along 
> with vector/matrix of complex sfixed and ufixed) such that the element 
> dimension can be defined at the same time as the array dimensions 
> would also be a major improvement to VHDL arrays and records - I think 
> this capability will be in the next VHDL revision correct?). For your 
> information I have had major success in converting Simulink 
> fixed-point models to VHDL using the current preliminary fixed-point 
> packages.  Pairing the VHDL fixed-point package with the Mathworks 
> Simulink and Link for ModelSim tool significantly speeds up conversion 
> time for the tools I use.  I feel once the VHDL fixed-point package is 
> officially released this will make things interesting for the 
> companies that are making automatic HDL code generation from high 
> level tools such as Simulink.
>
>  
>
> Comments about the 'ilength or 'flength?
>
>  
>
>  
>
> Scott D. Hoy
>
> Phone:301.286.2619
>
> NASA GSFC E-mail: scott.d.hoy@gsfc.nasa.gov 
> <mailto:scott.d.hoy@gsfc.nasa.gov>
>
> Honeywell - TSI E-mail: scott.hoy@honeywell-tsi.com 
> <mailto:scott.hoy@honeywell-tsi.com>
>
> Honeywell - TSI
>
> NASA Goddard Space Flight Center
>
>  
>
>  
>