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AR# 19186

6.2i XST - XST generates incorrect logic under certain arithmetic conditions

Description

Keywords: XST, arithmetic, logic, incorrect, integer

Urgency: Standard

General Description:
Under the following condition XST generates incorrect logic:

-- when using operation between std_logic_vector and unconstrained integer
out_addr := current_address - addr - current_count; --current count is an unconstrained integer

Solution

The work around for the above example is to convert the integer to a std_logic_vector as follows:

out_addr := current_address - addr - conv_std_logic_vector(current_count,6);

This problem has been fixed in the latest 6.2i Service Pack available at:
http://support.xilinx.com/xlnx/xil_sw_updates_home.jsp
The first service pack containing the fix is 6.2i Service Pack 2.
AR# 19186
Date Created 03/22/2004
Last Updated 07/18/2007
Status Archive
Type General Article