UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 22495

8.2i XST - What does the following error mean: "ERROR:Xst:772 - "Attribute is not authorized : 'succ'."?

Description

What does the following error mean?

"ERROR:Xst:772 - "Attribute is not authorized : 'succ'."

The following is my example code:

============================

type state_type is (s0, s1);

signal state : state_type;

begin

process (clk, reset)

begin

if (reset = '1') then

outdata <= '0' ;

state <= s0;

elsif rising_edge(clk) then

if (flag = '1') then

state <= state_type'succ(state);

else

state <= s0 ;

end if;

end if ;

end process ;

=================================

Solution

The VHDL LRM does not allow you to access user-defined attributes in this manner; consequently, the error message is correct. The LRM allows only the ability to access predefined attributes.

To eliminate this error, you can write your code as follows:

=============================================================

type state_type is (s0, s1);

signal state : state_type;

begin

process (clk, reset)

begin

if (reset = '1') then

outdata <= '0' ;

state <= s0;

elsif rising_edge(clk) then

if (flag = '1') then

state <= s1;

else

state <= s0 ;

end if;

end if ;

end process ;

=========================================================================

AR# 22495
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article