Riky Fitriadi Presentasi SKEmbedded CH08

8/10/2019 Riky Fitriadi Presentasi SKEmbedded CH08

1/17

Riky Fitriadi (23213061)

State Machine andConcurrent Process Model


2/17

Content

Models vs Languages

State Machine Model

FSM/FSMD

HCFSM and Statecharts Language

Program-State Machine (PSM) Model

Concurret Process Model

Communication

Syncronization

Implementation

Dataflow Model


3/17

Introduction

Describing embedded systems processing behaviorextremely difficult

Complexity increasing with increasing IC capacity

Desired behavior often not fully understood in

beginning Many implementation bugs due to description

mistakes / commission


4/17

Models and languages

How can we (precisely) capture behavior ? We may think of language (C, C++, Basic), but computation

model is the key

Common computation model :

Sequential program model Statements, rules composing statements, semantics for executing

them

Communicating process model

Multiple sequential programs running concurrently

State machine model For control dominated systems, monitors control inputs, sets control

outputs

Dataflow model

For data dominated systems, transforms input data streams into

output streams


5/17

Models vs languages

Computer models describe system behavior

Conceptual notion, e.g. recipe, sequential program

Languages capture models

Concrete from, e.g. English, C

Variety of languages can capture one model

E.g. sequential model -> C, C++, Java

One languages can capture variety of models

E.g. C++ -> sequential program model, object oriented model,

state machine model

Certain languages better at capturing certain computation models

Models

Languages


6/17

Text vs graphics

Model versus languages not to be confused with text versus graphics

Text and graphics are just two types of languages

Text : letters, numbers

Graphics : circles, arrows (plus some letters ,numbers)

X = 1;

Y = X + 1;

X = 1

Y = X + 1


7/17

Introductory example : An elevator

Controller

Simple elevator controller Request resolver

resolves various

floor requests into

single requested

floor Unit control moves

elevator this

requested floor

Partial English description :

Move the elevator either up or down to reach the requested floor. Once at the

requested floor, open the door at least 10 seconds, and keep it open until the

requested floor changes. Ensure the door is never open while moving. Dont

change directions unless there are no higher request s when moving up or nolower requests when moving down


8/17

Introductory example : An elevator

Controller

Try capturing in a sequential programming model like Cinput : int floor; bit b1..bN; up1..upN-1; dn2..dnN;

output: bit up,down,open;

global variable : int req;

Void UnitControl()

{

while(1)

{

while(req==floor);

open = 0;

if (req>floor)

{up = 1;

}

else {down = 1;}

up = down = 0;

open = 1;

delay(10);

}

}

Void RequestResolverl()

{

while(1)

{

req =;

}}

Void main()

{

Call concurrently:

UnitControl() and

RequestResolver()

}


9/17

Fomal Definition of Finite-state machine

(FSM) model Finite-state machines also calledfinite-state automata or justfinite

automata State Machine Model

FSM/FSMD (Finite state model with datapath)

HCFSM and Statecharts Language

Program-State Machine (PSM) Model

Formal FSM definition M = (X, Y, S, , , so)

X is the input alphabet

Y is the output alphabet

S is finite set of states

is the transaction

is the output function , : SY

So is initial state

High Level Finite State Machine (HLFSM)

Convert later to a FSM + D


10/17

Finite State Machine (FSM) Model

Trying to capture this

behavior as sequentialprogram is a bit awkward

Instead, we might

consider an FSM model,

describing the system as

Possible state. E.g. Idle,

GoingUp, GoingDown,

DoorOpen

Possible transaction from

one state to another based

on input. E.g. req > floor, re

< floor, etc.

Action that occur in each

state . E.g. up = 1, down,

open, and timer_start = 0

u is up , d is down, o is open, t is timer_start


11/17

HCFSM and the Statecharts languages

Hierarchical / concurrent

state machine model(HCFSM)

Extension to state machine

model to support hierarcy

and concurrancy

State can be decomposed

into another statemachine

With hierarchy has

identical functionality as

without hierarchy, but has

one less transition (z)

Known as OR-

Decomposition

State can execute

concurrently

Known as AND-

Decomposition

Without hierarchy With hierarchy

Concurrency


12/17

HCFSM and the Statecharts languages

Statecharts

Graphical language tocapture HCFSM

Numerous additional constructs

available to improve state

capture

History

Enter most recently visited

when return instead of

initial state

Timeout

Transition with time limitas condition

Transition taken if source

state active for defined

time limit

Many others joins, forks,conditional, selections,

History

Timeout


13/17

UnitControl with FireModeWithout hierarchy

FireModeWhen fire is true, move elevator to 1stfloor and open door


14/17

UnitControl with FireModeWithout hierarchy

FireModeWhen fire is true, move elevator to 1stfloor and open door


15/17

UnitControl with FireMode

Also add concurrency to our model


16/17

Program-state machine model (PSM)HCFSM plus sequential program model

Also add

concurrency to ourmodel

Extends state

machine to allow

use of sequential

code or FSM to

define state actions Includes hierarchy

and concurrency

extentions of

HCFSM

Stricter hierarchy

than HCFSM used in

Statecharts

Examples

SpecCharts :

extention of VHDL

SpecC: extention of

C

Black square originating within FireMode indicates !fire

is a transaction-on-completiontaken only if the conditionis true and program state is complete


17/17

Summary

Computation models are distinct from languages

Finding approriate model to capture embedded system is an importantstep

Model shapes the way we think of the system

Language should capture model easily

Ideally should have features that directly capture constructs of

model

Many choice

Sequential program model is popular

State machine model good for control

Extentions like HCFSM provide additional power Concurrent process model for multi-task systems

Communication and syncronization methods exist, scheduling is

critical

Dataflow model good for signal processing

Documents

Riky Fitriadi Presentasi SKEmbedded CH08