FREQUENTLY ASKED QUESTIONS
- Cadence crashed while I was working on a design. Now Cadence doesn't let me edit my
design, saying that it is locked.
Everytime a design is open for editing, Cadence locks it so that no other process
(or somebody else) can change it. It's a security feature.
Whenever Cadence crashes, it may happen that a design is left locked. In that
case, when you try to open it again, Cadence thinks the cell is still being
edited and doesn't let you change it. If this happens, here's how you can
unlock the design:
- Find the path to the affected cell. Just try to open it and
CIW will report the path.
- Build the following expression in the CIW prompt:
ddLockFree(ddLockPath("path to affected file"))
The locking service can take a long time to process the
request. If you still have problems opening cells, try the following:
- Exit from Cadence.
- At the shell prompt, type: setenv CLS_CDSD_COMPATIBILITY_LOCKING NO
- Restart Cadence and repeat the above ddLockFree command.
- If a spectreS simulation is interrupted for some reason (power glitch,
crash, etc), is there a way to continue the simulation from the point
where it broke?
Yes, there is a way. Here's how:
- Go down to the directory ~/simulation/cellname/spectreS/schematic/netlist,
where cellname is the cell schematic that you were simulating.
- Edit the file runSpectre, and add the option +recover
to the spectre command line.
- Invoke spectreS by typing runSpectre at the shell prompt. Spectre
will continue the simulation starting from where it was interrupted.
- Once the simulation finishes, the results can be loaded back into
Analog Artist by selecting Results->Select in the menu.
Important: Spectre will not append to the previous data file. It will
create a new one. Therefore, before restarting the simulation, you should save
the previous data using the Results->Save Results menu option.
- In SpectreS, how can I save simulation data points into a file?
One way is to use the printvs button in the calculator. However, this method
only allows for a maximum of 1900 points. If you need more, it's better
to use the Ocean command ocnPrint. In the CIW, type the following:
ocnPrint( v(out) ?output "./myOutFile" ?from A ?to B ?step step_size )
This will save data points of signal v(out), from point A to point B, in
increments of step_size, to the file myOutFile.
If you want to import the data in MATLAB, include the following in the above
command: ?numberNotation 'engineering
- Giving names to the wires:
Sometimes a design can have many connections. Connecting terminals
that are far apart or in awkward places can be difficult and can
make the schematic hard to understand.
It's easier to draw small pieces of wire on the terminals and to
give them the same name. Then, Design Framework II will consider that the terminals are
connected to the same net.
To name wires, do the following:
Create->Wire Name
Type the wire name, and click on the net.
- Looking at transistor parameters: (for spectreS only)
If you want to know a specific DC operating point parameter for a
transistor (gm, vdsat, etc), follow these instructions:
In the Analog Artist Simulation window, select:
Tools->Results Browser
Click OK in the project directory form.
The results browser window opens. This window can be used to
access any information related with the simulation. For example,
to find the gm of a transistor, follow this path:
schematic->psf->Run1->opBegin.info->[transistor]->gm
The results marked in yellow can be selected and pasted in the
calculator window (with the left mouse button), or directly in
the waveform window (with the right mouse button), depending on
their nature.
- Changing the number of digits displayed:
There is no menu command to do this. You have to use a SKILL
command (SKILL is the language on which Cadence is supported).
In the CIW (or log window), type:
aelPushSignifDigits(8)
...and press return.
Make sure you type the right capital letters.
This will change the number of significant digits to 8.