Hardware Reference
In-Depth Information
10.3
The Yevtushenko-Zharikova's Procedure
In this section, we present a procedure due to N. Yevtushenko and S. Zharikova
to compute sequential don't cares that capture a restricted form of flexibility, to be
applied for the resynthesis of a component in a network of FSMs (see [151, 153]).
Given the composition
M
A
M
B
in Fig.
10.9
, the procedure by Yevtushenko-
Zharikova works as follows:
1. Transform
M
A
and
M
B
into the corresponding automata
A
and
B
.
2. Derive the intersection
A \ B
"I O
.
3. Replace a transition from state
b
k
under input
u
j
in
B
by a don't care transition
1
if for each state
.a; b
k
/ 2 A\B
"I O
,
a 2 A
, there is no transition with an action
whose projection on
U
is
u
j
.
4. Let
M
B
be the final corresponding incompletely specified FSM.
Proposition 10.1.
Each FSM that is a reduction of FSM
M
B
can replace the
component FSM
M
B
without changing the behavior of the overall system.
Similarly, don't care transitions can replace care transitions in the component FSM
M
A
; they are inputs of
M
A
that cannot be produced in the composition as outputs
by the component FSM
M
B
.
I
O
M
A
U
V
M
B
Fig. 10.9
FSM composition
to illustrate
Yevtushenko-Zharikova's
procedure
Spec
1
A don't care transition goes to a designated DNC state and issues any output; at the state DNC
under any input there is a self-loop that issues any output.
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