Hardware Reference
In-Depth Information
Part III
Application to Sequential Synthesis
In this part of the topic, we look at the problem of sequential synthesis where a finite
state machine is embedded in a larger FSM environment. The problem addressed is
to find the set of all possible FSMs that can be used in place of the current FSM
without changing the externally observed behavior of the FSM environment. This
set is called the complete sequential flexibility, CSF, of the machine (with respect to
its environment), and is analogous to the complete flexibility used in combinational
synthesis. We will also show how to solve a number of examples in sequential
synthesis using scripts of the BALM system, thereby reinforcing the understanding
of its inner working from the user's point-of-view.
This part includes five chapters, of which the first four chapters address the
problem of computing the flexibility in sequential networks (maximum or restricted
flexibility); instead the last chapter discusses how to exploit the computed sequential
flexibility by extracting a valid replacement that is advantageous with respect to a
chosen cost function.
Chapter 10 reports some classical and new methods to compute restricted forms
of sequential flexibility, as sequential don't cares; it surveys the techniques of Kim-
Newborn, Wang-Brayton and Yevtushenko-Zharikova, illustrating some of them by
examples solved with BALM.
Chapter 11 discusses how to compute the sequential flexibility in a netlist given
in BLIF-MV or BLIF format, and then focus on a window, partitioning the netlist
into two parts - all nodes inside the window and all nodes outside the window.
The nodes inside the window can be viewed as a separate FSM and the nodes outside
the window as its fixed environment.
Chapter 12 addresses the problem of resynthesizing the component FSMs of a
network of FSMs; we will discuss both a global approach and a local (windowing)
approach. It will turn out that sometimes it is more effective to solve a system
of equations instead of a single equation; therefore we will introduce systems of
equations over FSMs.
Chapter 13 discusses the use of simulation relations which make language
solving easier for some topologies, but they do not always guarantee to compute
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