Java Reference
In-Depth Information
may happen that the output buffer gets unloaded before the production unit
completes the work, but if this does not happen the
WD
event cannot be
raised when the work is done.
Table 9.1 lists the states that describe the machine behaviour. It identifies
the enabled events for each admissible state. The resulting automaton
comprises eleven states.
9.2.3
The assembler finite state automaton
The assembler automaton comprises four states (see Figure 9.2):
■
E
: the input buffer is empty.
■
N
: the input buffer contains only nuts.
■
S
: the input buffer contains only screws.
■
W
: the assembler is working.
Three events determine state transitions:
■
SL
: a screw has been loaded in the input buffer.
■
NL
: a nut has been loaded in the input buffer.
■
WD
: a bolt has been assembled.
The
x
and
y
state variables represent the number of nuts and screws
in the input buffer. The automaton depicted in Figure 9.2 does not take
into account the possibility that the input and output buffers get full
and therefore the assembler cannot work. Similarly, it does not model the
BROKEN
and
REPAIRED
states.
Table 9.1
The list of states of the machine and the enabled events
States
Enabled events
Inadmissible
INPUT FULL
WORKING
OUTPUT FULL
INPUT FULL
WORKING
OUTPUT NOT FULL
WORKDONE
UNLOADED
INPUT FULL
WORKING
OUTPUT EMPTY
WORKDONE
INPUT FULL
NOT WORKING
OUTPUT FULL
UNLOADED
Inadmissible
INPUT FULL
NOT WORKING
OUTPUT NOT FULL
Inadmissible
INPUT FULL
NOT WORKING
OUTPUT EMPTY
Inadmissible
INPUT NOT FULL
WORKING
OUTPUT FULL
INPUT NOT FULL
WORKING
OUTPUT NOT FULL
LOADED
WORKDONE
UNLOADED
INPUT NOT FULL
WORKING
OUTPUT EMPTY
LOADED
WORKDONE
INPUT NOT FULL
NOT WORKING
OUTPUT FULL
LOADED
UNLOADED
Inadmissible
INPUT NOT FULL
NOT WORKING
OUTPUT NOT FULL
Inadmissible
INPUT NOT FULL
NOT WORKING
OUTPUT EMPTY
Inadmissible
INPUT EMPTY
WORKING
OUTPUT FULL
INPUT EMPTY
WORKING
OUTPUT NOT FULL
LOADED
WORKDONE
UNLOADED
INPUT EMPTY
WORKING
OUTPUT EMPTY
LOADED
WORKDONE
INPUT EMPTY
NOT WORKING
OUTPUT FULL
LOADED
UNLOADED
INPUT EMPTY
NOT WORKING
OUTPUT NOT FULL
LOADED
UNLOADED
INPUT EMPTY
NOT WORKING
OUTPUT EMPTY
LOADED
