描述

Urgency: Hot 

General Description: 

A simple latch functionally simulates properly, but fails in timing simulation.

解决方案

This is fixed in the latest version of the WebPACK XPLA Fitter Module, which is 

available for download at: http://www.xilinx.com/products/software/webpowered.htm
 

The work-around for older versions of software is to open the time_sim.vhd file and look  

for the process statement that contains the latch; add the data input into the sensitivity list. 

Example:  

process(LH, AP, AR, D) 

begin 

if AR = '1' then 

Q_local <= '0' after tar2q; 

elsif LH = '1' then 

Q_local <= D after tLDI; 

elsif AP = '1' then 

Q_local <= '1' after tap2q; 

end if; 

end process;