General Description: The output equations from arithmetic functions in an ABEL design, using the ABEL-XST flow in FISE 3.1i or Webpack ISE (3.1WP1.0 or later), are incorrect.
The symptom of this error is incorrect output values from XST synthesis. The incorrect values will show up in both the fitting report and timing simulation. No warnings will be issued. Note that functional simulation using BLIFSIM will appear to be correct.
This problem has been fixed in 3.1i service pack 6 and later software
This error is due to a problem in the AIM library used in the ABEL-XST flow. The error causes input components of an arithmetic bus equation to be concatenated in the reverse order; then, the MSB is treated as the LSB in all inferencing models (addsub and compare).
The recommended workaround is to disable "Enable Arithmetic Inferencing" in the Synthesis process properties dialog.
The problem does not occur using the ABEL-BLIF flow in FISE or Webpack ISE, nor in Foundation 3.1i (Aldec-based) product.