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VLSI Digital Signal Processing Systems: Design and Implementation by Keshab K. Parhi

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5.7    PROBLEMS

  1. Unfold the DFG in Fig. 5.20 using unfolding factors 3 and 4.
  2. Unfold the DFGs in Fig. 5.21 using unfolding factors 2 and 5.
  3. Prove the relationship in (5.3) used to show that unfolding preserves the number of delays.
  4. This problem attempts to show that a complex loop, which is a combination of 2 simple or fundamental loops, cannot introduce a new iteration bound. To show this, consider two loops with loop computation times T1 and T2, respectively, and with number of delay elements N1 and N2, respectively. Let T1/N1 > T2/N2 hold. Show that

    image

  5. Our objective in this problem is to prove that the critical path of a J-unfolded DFG is a monotonically nondecreasing function with respect to J [11]. To show this, prove that the critical path of a J-unfolded DFG is greater than or equal to the critical path of the (J − l)-unfolded DFG.
  6. Prove that the following iterative algorithm computes the minimum unfolding factor for a nonrecursive DFG such that the iteration period of T is achievable. It is assumed that pipelining and/or retiming are not used to reduce the critical path.

    Repeat until TcritJT

    {

    image

    image

    Fig 5.19    (a) The DFG in Fig. 5.16 redrawn so it is compatible with the unfolding ...

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