Tutorials:Cadence:AdvancedTopics
Advanced Topics
Pad frame
One tiny chip unit is 1.5mm x 1.5mm. The pad frame provided here has a total of 40 pins. The 4 corner pins are used for VDD and GND (note the +/- symbols in the layout) and the remaining 36 pins are available for I/O.
To use the pad frame, please do the following steps:
- Download Padframe_C5N.tgz into $HOME/cadence/library.
- Type "cd $HOME/cadence/library".
- Type "tar -xzvf Padframe_C5N.tgz". This will extract the pad library.
- Type "cd ..".
-
Edit cds.lib and add the following line:
DEFINE pad library/pad
- Execute virtuoso. The pad library will now appear in the Library Manager.
The pad frame layout is shown below.
Vector File Simulation
Now we are introducing a new simulation method under Cadence Spectre Simulator: Using Vector File. Vector file is a very convenient way to do large scale digital simulation, the manual for how to write digital vector file can be download from here:
In Cadence, first we create a NAND2 cell schematic view:
In this NAND2, we have two input ports: A and B, one output ports: C. Then in vector file, we assign values to A and B. The example vector file NAND2.vec:
In a basic vector file, you need define the radix, i/o, tunit, and value for the input or output ports, moreover, you can also define your rise/fall time, high/low voltage. Next, we open the Cadence ADE L:
Then left click Setup->stimuli..., the window of stimuli will jump out:
Then left click to select the Globe Sources at the first row, then select vdd!, click select enable, fill the DC voltage with a value, here we just define it 3V, (Note: by giving the value to vdd! here, we don't need to load vdc module anymore), then click apply:
After we click OK, the window will disappear, we left click Setup-> Simulation Files, then select "Vector Files" tab at the top row, add NAND.vec as the Vector Files:
Click OK, then left click choose Analyses-> Choose..., on the "Choosing Analyses" tab, select tran, then fill the stop time with a value, here we fill it as 40n s:
Click OK, then select the ports you want to view in the schematic by using Outputs-> To Be Plotted-> Select On Schematic, then click Netlist and Run button:
Finally, we get the waveform of this NAND2 gate:
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