Restricted Fmax

Let's look at the problem, about which I wrote earlier on a very simple example - an 8-bit counter lpm_counter.

Using Quartus 13.0sp1 Web Edition.

Device Cyclone II EP2C35F672C6.

Fmax = 518.4 MHz

Restricted Fmax = 420.17 MHz

Clock constraint assigned in value of 420 MHz.

1. Perform functional simulation project using the ModelSim Altera Starter Edition, clock - 420 MHz

http://www.alteraforum.com/forum/attachment.php?attachmentid=11622&stc=1

We get the normal simulation results.

2. Perform timing simulation project using the ModelSim Altera Starter Edition, clock - 420 MHz

http://www.alteraforum.com/forum/attachment.php?attachmentid=11623&stc=1

We get zero values on the outputs of the counter.

3. However, if you run the simulation time when clock = 420 MHz is not in ModelSim, and Quartus II Simulator - get the normal output value of the counter:

http://www.alteraforum.com/forum/attachment.php?attachmentid=11624&stc=1

4. ModelSim Altera Starter Edition shows a non-zero values at the outputs of the counter only if the clock frequency reduced to 320 MHz or less:

http://www.alteraforum.com/forum/attachment.php?attachmentid=11625&stc=1

How to Decide this problem with ModelSim simulation at a frequency of at most 320 MHz?

Thanks