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AR# 10412

3.1i XST - Limitation on "shreg_extract" attribute

Description

Keywords: SRL, SRL16, extract, attribute, property

Urgency: Standard

General Description:
If the shift register is described with separate signals for each register flip-flop, the "shreg_extract" attribute only works if it is set for all those signals. (A future enhancement will allow users to set the property on only one of the signals.)

NOTE: This problem is fixed in the 4.1i software release.

Solution

Attach the shreg_extract attribute to every signal.

Example:

:
attribute shreg_extract : string;
attribute shreg_extract of d1, d2, d3, d4, d5, d6, d7, d8 : signal is "no";
:
:
process(clk)
begin
if (clk'event and clk='1') then

d8 <= d7;
d7 <= d6;
d6 <= d5;
d5 <= d4;
d4 <= d3;
d3 <= d2;
d2 <= d1;
d1 <= di;

end if;
end process;
:
:
AR# 10412
Date Created 10/31/2000
Last Updated 08/19/2002
Status Archive
Type General Article