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AR# 12481

4.1i Core Generator Reed Solomon v2.0 - 4000E Physical simulation without SDF works but with SDF fails when using global reset

Description

Keywords: RS, Forward Error Correction, encoder, decoder

Urgency: Standard

General Description:

In my Reed Solomon decoder core I get simulation failures with the 4000E family where I use the SDF file in physical simulations. If I don't use the SDF file or I change to a 4000xl family for example the simulations work fine.

Solution

This has been traced this problem to the way in which reset is handled by the
X_FF component. Using the GSR signal to reset the core at startup and you will
notice that there is a significant delay between the rst and the rst_ipd in the 4000E family. This delay results in the fact that the output of this FF is delayed by one clock cycle in the 4000E case compared with the 4000XL case. This delay causes the simulation to fail. If you run the simulation without the SDF file or with the 4000XL family this unwanted delay does not appear.

The workaround is to not use the SDF file during physical simulation when using
v2.0 of the Reed Solomon and targeting the XC4000E family.

Logical Simulation - NGM file is used in NGDAnno
Physical Simulation - NGM file is not used in NGDAnno
AR# 12481
Date Created 09/05/2001
Last Updated 05/13/2009
Status Archive
Type General Article