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Project 2: Cadence Help. Fall 2005 EE 141 Ke Lu. Design Phase. Estimate delay using stage effort. Example: 8 bit ripple adder driving a final load of 16. Rough estimate of Area. Sum over the size times LE of every gate. Schematics: Using Hierarchy. 1. Transistor Level.

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project 2 cadence help

Project 2: Cadence Help

Fall 2005 EE 141

Ke Lu

design phase
Design Phase
  • Estimate delay using stage effort. Example: 8 bit ripple adder driving a final load of 16.
  • Rough estimate of Area. Sum over the size times LE of every gate.
1 transistor level
1. Transistor Level
  • Remember to use nmos4 and pmos4.
  • Make sure you have the right tech lib attached. 0.24u process.
  • Connect input and output pins accordingly.
2 creating symbol from schematic
2. Creating Symbol from Schematic
  • In Schematic view, click Design->Create Cell View->From Cell View.
  • Don’t bother making the symbol shape pretty because Cadence will crash.
3 putting the blocks together
3. Putting the Blocks Together
  • Use “i” to instantiate symbols to build more complicated schematics.
  • Use “l” hot key to label wire names to simplify connecting the blocks together. Example, VDD and GND.
extracting netlist
Extracting Netlist
  • In Schematic view, open the analog environment window by clicking Tools-> Analog Environment.
  • Go to Setup-> Environment and change the settings to hSpice and hierarchal.
  • Next go to Setup-> Simulator/Directory/Host and change the Project Directory.
  • Finally, click Simulation-> Netlist-> Create Final
  • Cadence will put the netlist in CELLNAME/ hspiceS/extracted/netlist/hspiceFinal
  • Fix the model file by adding “.lib g25.mod TT”, change TSMC25DN to NMOS, and edit the .OPTION statement.
layout
LAYOUT
  • Pitfalls
    • Doing LVS after laying out the entire adder.
    • Not running DRC often.
    • Not budgeting space for routing.
  • Plan ahead to avoid these. Otherwise, Cadence will make life miserable.
how to pass lvs
How to Pass LVS
  • Plan ahead before laying out. Do stick diagrams first.
  • Do LVS “incrementally.”
  • Example, mirror adder.
summary
Summary
  • START EARLY. Cadence will hang as more and more people use the machines.
  • Check Design often, run DRC often. Catch bugs early.
  • Worst case tp*A = 6 uS * um^2. You must do better.