Re: [f-cpu] HDL coding rules

[Etienne LABARRE <etienne.labarre@gadz.org>]

On Tue, Jul 30, 2002 at 01:58:29PM +0200, Just an Illusion wrote:
> Hi,
> 
> I have forgot some thing
> 
> Just an Illusion wrote:
> 
> >Hi,
> >
> >Yann Guidon wrote:
> 
> <cut>
> 
> >>
> >>maybe you can look at the code and see yourself.
> >>
> >Ok, I have done it.
> >
> >Please, Etienne forgive me, but your code can be a good example to 
> >illustrated this subject.
> >
> >In the eu_inc.vhd file :
> >
> >* some keywords are in capital letter, some others not.
> >* The generic parameter eu_inc_width can be put in capital letter, to 
> >help distinction with signal and variable value.
> >* The interface signals aren't globally in capital letter except for 
> >function  abs_chunk.
> >
> >That doesn't change the result, but can help the code reading.
> >
> >The next remark is not a "coding rule", but more a "coding style" rule.
> >
> >I thing is better if you create a package which embedded all the 
> >necessary component (and perhaps functions) needed for your eu_inc and 
> >eu_cmp rather than "use work.find_lsb;" notation.
> 
> I have an other one (coding style) :
> 
> Defined each value of eu_inc_mode by a constant, and use them into the 
> case structure. Something like :
> ...
> architecture simple of eu_inc is
> ...
> constant C_EU_INC_MODE_NEG  : natural := "000"
> constant C_EU_INC_MODE_DEC   : natural := "001"
> constant C_EU_INC_MODE_INC    : natural := "010"
> constant C_EU_INC_MODE_ABS   : natural := "011"
> constant C_EU_INC_MODE_LSB0 : natural := "100"
> constant C_EU_INC_MODE_LSB1 : natural := "101"
> ...
> begin
> ...
>   eu_inc_in : process(eu_inc_A, eu_inc_simd, eu_inc_mode) is
>   begin
>     -- Input of unit
>     case eu_inc_mode is
>        when C_EU_INC_MODE_NEG   => tree_in <= not eu_inc_A;
>        when C_EU_INC_MODE_DEC   => tree_in <= not eu_inc_A;
>        when C_EU_INC_MODE_INC    => tree_in <= eu_inc_A;
>        when C_EU_INC_MODE_ABS    => tree_in <= not eu_inc_A;
>        when C_EU_INC_MODE_LSB0  => tree_in <= eu_inc_A;
>        when C_EU_INC_MODE_LSB1  => tree_in <= not eu_inc_A;
>        when others => tree_in <= eu_inc_A;
>     end case;
>   end process;
> ...
> 
> Now, if you want change the eu_inc_mode coding values, you need modify 
> it only in one place.
> 
> See the coding rule I have use to immediatly link (when read) the 
> constant value with the content of eu_inc_mode.

Ok, il will modify my code. I don't wait the document had written :-)

Etienne
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