Dr. Vered Gafni – Real time systems development by the formal approach 1 The Design Language of...
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Dr. Vered Gafni – Real time systems development by the formal approach 1
The Design Language of Statecharts
Dr. Vered Gafni – Real time systems development by the formal approach 2
The Design Language of Statecharts
Finite State Machine • R, S, T – States• a, b, c, d - Events• Arrows - State transitions
Event: a, b, c, ... a or/and b not a dly(t), tm(a,t) tr(C)/fs(C)
Conditions: A, B,... A or/and B not(A) in(S) x=y, x<y,….
Actions: a,b,… tr!(C)/fs!(C) x := vrd!(x)
Initial state
optional
Dr. Vered Gafni – Real time systems development by the formal approach 3
Examples
Split on condition
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Sub-States: Sequential Refinement
• S is a super-state w.r.t {S1, S2, S3 }
• Super-state transitions (priority)
• History entrance (H* -deep history)
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Example of Sequential Refinement
Equivalence
up to priorities
done[B]/fs!(B)
A
Failure
done[A]\fs!(A)
B
C
fail/tr!(A)fail/tr!(B)
fail/tr!(C)
done[C]/fs!(C)
/fs!(A),fs!(B),fs!(C)
A
Failure
doneB
C fail
H
Dr. Vered Gafni – Real time systems development by the formal approach 6
Sub-states: Parallel Refinement
Events broadcasting
S3.A
S1 S2
S3
S
S2.A
S1.A
S1.B
S1.C
S2.B
S3.B
a
b\m
c\tr!(C)
m
tm(m,3sec)
tr(C)
f
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• Delay: To turn on the furnace open the oil valve, and after 3 seconds activate ignition
Specification of Time Constraints
RTC tick
Dly(100mls)/tick Wait Period
Control loop
done
• RTC: Execute control loop at 10Hz rate
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Delay as Deadline
• Deadline: Whenever train enters XR, gate should be closed within 10 seconds; otherwise an alarm will be activated
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Where Timeout is useful?
Far
Nearexit
enter
tm(enter,3)/close_cmdOpen
Close
dly(15)/open_cmd
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Synchronization Techniques I
R
S
P
A
B
T
a
b
C/end; ff
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Synchronization Techniques II
R
S
P
A
B
b
fc/tr!(K)
Q
g
a
C
[K]
U [not(K)]
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Synchronization Techniques III
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Controllertrain-in train-out
go,
stop close,
open
position
Example: Railroad crossing
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Crossing Control: Sequential Design
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Crossing Control: Parallel Design
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Example: Automatic Cruise Control
on off
ACC
Car Motion ProcessSpeed Throttle
resumebutton
gas/brakespedals
masterswitch
command lever
Engine
IMD
RPM Gear
Dr. Vered Gafni – Real time systems development by the formal approach 17
Automatic Cruise Control
ACC
Disabled
Enabled
Inactive
Active
engine-onengine-off
Operating
Suspended
start-acc
stop-acc
abort
resume
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State Operating (sub-state of Active)
CommandMonitor
SpeedControl
GearControl
Operating
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State CommandMonitor (component of Operating)
Dr. Vered Gafni – Real time systems development by the formal approach 20
SpecialNormallow
drive
2 1tr(rpm<=3K) tr(rpm<=1K)/low
tr(rpm>1k) tr(rpm>3K)/driveDrive
[rpm<=1K]/low[rpm>3K]
[rpm<=3K and rpm>1K]
c
CommandMonitor
GearControl
SpeedControl
Operating
Dr. Vered Gafni – Real time systems development by the formal approach 21
StatemateA Real-Time Design Tool
Provides for representation of 3 system views:
• What:
- the activities the system should do, and inter-activities data flow
• When:
- the timing and synchronization of activities activation and data transfer
• Where:
- in what subsystem the each activity should be implemented
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Dr. Vered Gafni – Real time systems development by the formal approach 23
Basic Components
A
A1
A2
A3
C
A2_1
A2_2
E1E2
E3
CC
u
v wq
e
f
h
r
x
s
fff
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