Description

The following error occurs in XST when I target Virtex-6 or Spartan-6 devices, but I do not have any issues targeting older devices. Why?

ERROR:HDLCompiler:16 - "<file>.vhd" Line xx: <width> cannot be used within its own interface list. Please verify that you don't use this object for the definition of other interface components.

Example code:

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

entity ex_0018 is

port(in_port : in std_logic_vector(7 downto 0);

out_port: out std_logic_vector(7 downto 0));

end ex_0018;

architecture beh of ex_0018 is

procedure add_0018 (

constant width: integer:=8; -- Note: Error point here

signal inp: in std_logic_vector(width-1 downto 0);

signal outp: out std_logic_vector(width-1 downto 0)) is

begin

outp <= inp + 5;

end add_0018;

begin

add_0018(inp=>in_port, outp=>out_port);

end;

Solution

In the above code, the constant width is declared and used in the add_0018 procedure interface list. This is not a VHDL LRM compliant code. To solve this issue, declare the constant width outside the procedure boundaries as shown below.

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

entity ex_0018 is

port(in_port : in std_logic_vector(7 downto 0);

out_port: out std_logic_vector(7 downto 0));

end ex_0018;

architecture beh of ex_0018 is

constant width: integer:=8;

procedure add_0018 (

signal inp: in std_logic_vector(width-1 downto 0);

signal outp: out std_logic_vector(width-1 downto 0)) is

begin

outp <= inp + 5;

end add_0018;

begin

add_0018(inp=>in_port, outp=>out_port);

end;

In 11.2, XST introduced a new VHDL/Verilog parser for Virtex-6 and Spartan-6 families. For more information on this change, see (Xilinx Answer 32927).