procedure

What is wrong with this?

procedure gen_s (
variable si, di : in std_logic_vector(z_width downto 0);
variable so : out std_logic_vector(z_width downto 0)) is
begin
if si(z_width) = '1' then
so := (si(z_width-1 downto 0) & '0') + di;
else
so := (si(z_width-1 downto 0) & '0' - di);
end if;
end gen_s;


I get errors about the + and - being infix operators in Modelsim, below.

# ** Error: C:/dividers/div_uu.vhd(72): No feasible entries for infix op: "+"
# ** Error: C:/dividers/div_uu.vhd(72): Bad right hand side in assignment.
# ** Error: C:/dividers/div_uu.vhd(74): No feasible entries for infix op: "-"
# ** Error: C:/dividers/div_uu.vhd(74): Bad right hand side in assignment.


Thanks.

Salman

Salman Sheikh

Salman Sheikh wrote:
> What is wrong with this?
>
> procedure gen_s (
> variable si, di : in std_logic_vector(z_width downto 0);
> variable so : out std_logic_vector(z_width downto 0)) is
> begin
> if si(z_width) = '1' then
> so := (si(z_width-1 downto 0) & '0') + di;
> else
> so := (si(z_width-1 downto 0) & '0' - di);
> end if;
> end gen_s;
>
>
> I get errors about the + and - being infix operators in Modelsim, below.
>
> # ** Error: C:/dividers/div_uu.vhd(72): No feasible entries for infix op: "+"
> # ** Error: C:/dividers/div_uu.vhd(72): Bad right hand side in assignment.
> # ** Error: C:/dividers/div_uu.vhd(74): No feasible entries for infix op: "-"
> # ** Error: C:/dividers/div_uu.vhd(74): Bad right hand side in assignment.
>
>
> Thanks.
>
> Salman
>

Salman,

You can't do calculations on a std_logic_vector. Try using signed or
unsigned in stead.

Kind regards,

Yves

Yves Deweerdt

Salman Sheikh wrote:
> What is wrong with this?
>
> procedure gen_s (
> variable si, di : in std_logic_vector(z_width downto 0);
> variable so : out std_logic_vector(z_width downto 0)) is
> begin
> if si(z_width) = '1' then
> so := (si(z_width-1 downto 0) & '0') + di;
> else
> so := (si(z_width-1 downto 0) & '0' - di);
> end if;
> end gen_s;

Not too much.

Add this to the top of your entity:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

and change std_logic_vector to unsigned.

-- Mike Treseler

Mike Treseler