Hi all! I am experiencing a very strange and rather frustrating problem while trying to run the same backannotated simulation in two different versions of Modelsim. In both cases I am using exactly the very same files for everything, and also the same compilation and simulation commands. The old version (Modelsim 5.8b) simulates fine and gives the expected results, while a newer release (Modelsim 6.2e) gives erroneous results. The following caption explains the situation (copy and paste the following link in your browser):
In the figure at the link above you can see the two simulations:
****[Upper part of image: Modelsim 5.8b - Results: OK, as expected] Notice pulse on signal "RNet7947' begining @ 10263ns and falling @ 10353ns. This is an update signal that is correctly fetched by the clock "RNet7665" @ 10353ns. The good, expected behavior is that the data in signal "WIR_shift" is updated to signal "PER/WIR", as shown.****[Lower part of image: Modelsim 6.2b - Results: WRONG, unexpected] Notice pulse on signal "RNet7947' this time begins @ 10264ns and falls @ 10354ns, too early to be fetched by the clock "RNet7665" (see carefully). Thus, the signal "WIR_shift" is NOT updated to signal "PER/WIR", which remains in "000", as shown.
I would be the most grateful if anybody could please give a clue to what is going wrong here. I REALLY need to get version 6.2e to run correctly with my design. The simulation command issued in both versions is as follows: vsim -sdfmin /ram_16kx16_tap_top_tb_p1500/dfm_0=DFM_TC_Best.pt.sdf
-sdfnoerror -sdfnowarn -t ns +mindelays work.ram_16kx16_tap_top_tb_p1500
In both cases I am using the same SDF file, with has the following header: (DELAYFILE (SDFVERSION "OVI 3.0") (DESIGN "DFM_TC") (DATE "Fri Nov 24 16:01:11 2006") (VENDOR "COREM10LPHVT CORXM10LPHVT IOLIB_65_M10_CUP_FT_TEST_1V2 PRM10 splpll_16Kx8") (PROGRAM "Synopsys PrimeTime") (VERSION "V-2003.12-SP1-3") (DIVIDER /) // OPERATING CONDITION "Best::Best" (VOLTAGE 1.32::1.32) (PROCESS "0.8000::0.8000") (TEMPERATURE -40.00::-40.00) (TIMESCALE 1ns) ...
Thanks in advance!!! Regards, JL.