1. Digital Filter Design Tools
Eric Hill
Lixin Su
ECE 734

2. Outline
Motivation
Accomplishments
Conclusion

3. Motivation Large design space Many different design goals
Many transformations available to optimize filter design
Many different design goals
Clock period, hardware cost, power consumption
All interdependent, tradeoffs required
Designers need automatic design tools

4. Project Goals Create an automatic design tool
Rapidly explore design space
Lower total design overhead
Open-ended
High level input format
Graphical representation

5. Current Status Features Implemented Graphical Representation
Retiming (clock and register minimization)
Folding (limited functionality)
Unfolding
Iteration bound, critical path calculation
Support for high level input format

6. Visualization Used Graphviz graph drawing software
Developed by AT&T Research Lab
Our design tool generates output files which are readable by Graphviz x + D 2D

7. Retiming Clock Period Minimization (Sec 4.4.2)
Create the Constraint graph for the original DFG
Apply Floyd-Warshall algorithm to derive all-pairs shortest path
Apply all possible clock periods to find the smallest possible clock period

8. Retiming Register Minimization (Sec 4.4.3)
Derive feasibility constraints from the original DFG
Create a new DFG by inserting dummy nodes
Create the constraint graph for the new DFG
Apply Floyd-Warshall algorithm to derive clock period constraints
Derive the cost function from the new DFG
Use Matlab (linprog) or GAMS to solve the linear programming problem (defined by the cost function, feasibility constraints and clock period constraints)

9. Clock Minimization Clock = 3 Clock= 2 Regs = 4 Regs = 5 New DFG
Original DFG

10. Clock & register minimization
Regs = 4
Clock = 2
Regs = 4
Original DFG
New DFG

11. Folding It supports limited functionalities.
Check if a folding scheme is possible
Minimize the clock period under one folding scheme

12. Conclusion Experiences from design
Input format is important to the success of a tool
Algorithm implementations are the most time-consuming part
GUI is important

13. Questions I have no professional training. I already gave my best.
I have no regrets at all.
-- William Hung on American Idol