Intel® Quartus® Prime Software
Intel® Quartus® Prime Design Software, Design Entry, Synthesis, Simulation, Verification, Timing Analysis, System Design (Platform Designer, formerly Qsys)
Announcements
FPGA community forums and blogs on community.intel.com are migrating to the new Altera Community and are read-only. For urgent support needs during this transition, please visit the FPGA Design Resources page or contact an Altera Authorized Distributor.
17268 Discussions

modelsim analog waveform transients

Altera_Forum
Honored Contributor II
2,219 Views

I'm using modelsim-Altera to make a gate-level simulation of an own ifft core, the target platform is an Stratix II FPGA.  

 

When i select the analog waveform display format for a signed 16 bits port corresponding to a Synthesized sine wave , i get in the picture some peaks (like glitches) that take random and big values, however the sine wave has an amplitude of 64. The basic sine shape looks well. I notice that this peaks appear before the t_su completion.  

 

I tried with a RTL simulation, however the ram memories in design (m4k's and m512's) don't work well.  

 

There is a way to define a trigger source, Such that the analog waveform display is sampled after every rising edge of a clock signal?. 

 

Why the ram memories don't work in the RTL-simulation? 

 

I appreciate any help with this. 

 

Regards, 

 

Alex Parrado
0 Kudos
4 Replies
Altera_Forum
Honored Contributor II
1,268 Views

I think, the glitches in analog waveforms are corresponding to glitches in the displayed signal. Resampling the data before displaying them should help. 

 

I performed RTL and gate-level simulations of designs with RAM blocks and wasn't aware of any ModelSim issues in this regard. What do you mean with don't work well?
0 Kudos
Altera_Forum
Honored Contributor II
1,268 Views

i run the rtl-level simulation and de data before the memories ports is correct, after of them the data is wrong. modelsim shows a warning referring to the clock edge in that the reading is made.

0 Kudos
Altera_Forum
Honored Contributor II
1,268 Views

haw can i do the resampling using modelsim?

0 Kudos
Altera_Forum
Honored Contributor II
1,268 Views

I didn't exactly understand what's the timing problem releated to memory operation. But if the data is stable a the clock edge, I meant you can simply add a register in your simulation, clocked from the said clock. 

 

The user manual tells about an option to sample signals at a clock edge, but I'm not sure if it applies only to the list window or also to the waveform window.
0 Kudos
Reply