Simulating VHDL design with ModelSim

[Modukuri]

Hi:

I'm using ModelSim SE-64 PLUS 5.5f to simulate my VHDL
designs.Recently,I tried simulating a design with input data files of
size (85kb).I left the simulation to run overnight,but I still haven't
got any results.I checked the status of "vsim"
by typing in the following at the command prompt.
ps -ef | grep vsim

It showed that vsim is still running and the CPU usage is only 25%.
I'm not sure if this is due to the file size???

Please help!!

Thanks,
Modukuri

 

[Ralf Hildebrandt]

I'm using ModelSim SE-64 PLUS 5.5f to simulate my VHDL
designs.Recently,I tried simulating a design with input data files of
size (85kb).I left the simulation to run overnight,but I still haven't
got any results.

Do you simulate behavioral descriptions or synthesitzed netlists (with sdf)?

What happens, if you stop the simulation (an run it again, starting from
the stop position)?


Check your source code for infinite loops:

process(enable,data)
begin
if (enable='1') then -- latch
data<=data+1; -- infinite loop - DON'T DO THIS
end if;
end process;


Ralf

 

[Modukuri]

I'm simulating behavioral descriptions (using vsim GUI).AS modelsim
window is not responding during the simulation,I'm unable to break the
simulation at any point except to kill the whole process.But that is
closing vsim completely.Is there any way to check,if the process is
actually updating the signals/ just executing the loops infinetely?
Below is part of my code.I tested my code in parts and it was working
fine until this process.I'm not sure, if the loops are causing the
problem??

process(clk,reset,sdata,cdata)
variable current_blk : data_array;
variable search_blk : data_array;
begin
if reset = '1' then
current_blk := data1;
search_blk := data1;
SAD_CMP <= SAD_ini;
elsif (clk'event and clk = '1') then
for m in 1 to 36 loop
for n in 1 to 44 loop
for i in ((m-1)*blksize) to ((blksize*m)-1) loop
for j in ((n-1)*blksize) to ((blksize*n)-1) loop
current_blk(i,j) := cdata(i,j);
cblk(i,j) <= current_blk(i,j);
for k in 0 to 3 loop
for l in 0 to 3 loop
for x in ((i-1)+pvec(k)) to ((i+pvec(k))) loop
for y in ((j-1)+pvec(l)) to ((j+pvec(l))) loop
if (x <= 143 and y <= 175) then
search_blk(x,y) := sdata(x,y);
sblk(x,y) <= search_blk(x,y);
for u in 0 to 143 loop
for v in 0 to 175 loop
if (sblk(u,v) >= cblk(u,v)) then
SAD_CMP(u,v) <= sblk(u,v) - cblk(u,v);
else
SAD_CMP(u,v) <= cblk(u,v) - sblk(u,v);
end if;
end loop;
end loop;
end if;
end loop;
end loop;
end loop;
end loop;
end loop;
end loop;
end loop;
end loop;
end if;

I would appreciate any help/advice.

Thanks a lot,
Modukuri

 

[Mike Treseler]

I'm simulating behavioral descriptions (using vsim GUI).AS modelsim
window is not responding during the simulation,I'm unable to break the
simulation at any point except to kill the whole process.

process(clk,reset,sdata,cdata)

Try process(clk,reset)
and make sure your sim clock waits when done.

--Mike Treseler

 

[Marcus Harnisch]

Check your source code for infinite loops:

Versions of ModelSim I work with, exit from zero-time loops after
5000(?) cycles by default.

Modukuri seems to be concerned whether the loop updates signals at
all. Why not do a `run x ns', where `x' is the time it takes to
simulate a reasonably low number of clock cycles.

With loops like that I wouldn't recommend single stepping but printing
time stamps and loop variables can give valuable information, too.

-- Marcus

 

[Tim Hubberstey]

I'm simulating behavioral descriptions (using vsim GUI).AS modelsim
window is not responding during the simulation,I'm unable to break the
simulation at any point except to kill the whole process.But that is
closing vsim completely.Is there any way to check,if the process is
actually updating the signals/ just executing the loops infinetely?
Below is part of my code.I tested my code in parts and it was working
fine until this process.I'm not sure, if the loops are causing the
problem??

Have you REALLY considered what you are doing here? Because of the
loops, the simulator must execute several hundred million iterations FOR
EACH CLOCK CYCLE, depending on the size of 'blksize'.

Even on the fastest workstation available, this is likely to take many
seconds per simulated clock cycle. I wouldn't be surprised to find that
it is many minutes, or even hours, per clock.

I also wouldn't be surprised to find that you've run out of physical
memory and forced the machine to start swapping. If this happens, your
simulation times will skyrocket.

As for ModelSim not responding to break requests, the last time I used
SE (several years ago) there was an issue with it not recognizing breaks
unless at least one signal was waved or logged (add [wave|log]).

 

[Allan Herriman]

Versions of ModelSim I work with, exit from zero-time loops after
5000(?) cycles by default.

Ummm, no. Only if delta time advances.

Regards,
Allan.

 

[Marcus Harnisch]

Ummm, no. Only if delta time advances.

Yes. But in the code example I was following up on delta time does
advance.