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AR# 22811

8.1i XST - XST produces a warning " WARNING:Xst:647 - "unable to assign to aggregate signals, and writes out incorrect logic

Description

XST is unable to assign a value to aggregate signals of record type.

Example that does not work:

architecture a of bug is

type t is record

q : std_logic_vector(15 downto 0);

end record;

signal s : t;

begin

s <= ( q => d ); -- line to change

q <= s.q;

end a;

Solution

XST generates incorrect logic for this design.

To work around this issue, rewrite this code as below:

architecture a of bug is

type t is record

q : std_logic_vector(15 downto 0);

end record;

signal s : t;

begin

s.q <= d; -- line changed

q <= s.q;

end a;

This issue will be fixed in ISE 8.2i.

AR# 22811
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article