Page 27 - DSP Integrated Circuits

12 Chapter 1 DSP Integrated Circuits

and maximum life cycle costs, etc. Furthermore, a time schedule for the successful
completion of the design and target dates for production and market introduction
are important issues.
A specification has two main parts, as illustrated in Figure 1.11.

Q A behavioral description that specifies what is to be designed and
Q A verification or validation part that describes how the design should be
verified (validated).
Verification involves a
formal process of proving the
equivalence of two different
types of representations
under all specified condi-
tions. Verification of a whole
system is rarely done in Figure 1.11 Specification
practice because of the large
complexity involved. However, small circuits and modules as well as simple com-
munication protocols represent practical problem sizes.
Validation is an informal and less rigorous correctness check. Validation is
usually done by simulating the circuit with a finite set of input stimuli to assert
that the circuit operate correctly.
A correct and complete specification of the system to be designed is crucial [4].
Recent experience shows that of all custom-designed VLSI circuits that do not work
properly, up to 70% of the circuits work without logical or electrical errors, but they
do not work in their intended environment. Their specifications, particularly the
specifications of the working environments, are erroneous or incomplete. Specifica-
tion and design problem capture are difficult and not well understood problems.

1.6.2 Partitioning Techniques
Generally, the system design phase consists of a sequence of partitioning steps
wherein the system is partitioned into a set of subsystems that are so simple that
they can be implemented without difficulty. Partitioning can be performed using
different strategies, but most strategies involve a hierarchical partitioning of the
system with the aim of reducing design complexity.

Data-Flow Approach
One approach is to partition the sys-
tem along the data-flow in the sys-
tem. If the data-flow graph is drawn
with data flowing from left to right
we can define vertical and horizontal
partitioning as illustrated in Figure
1.12. The former partitions the sys-
tem into parts that pass data in a
sequential manner while the latter
partitions the system into parts Figure 1.12 (a) Vertical and (b) horizontal
where data flow in parallel paths [5]. partitioning.