1. Essential Issues in Codesign: Models
Part of
HW/SW Codesign of Embedded Systems Course (CE )
Winter-Spring 2001
Codesign of Embedded Systems

2. Codesign of Embedded Systems
Today programme
Essential issues in codesign
Models
Architectures
Languages
Winter-Spring 2001
Codesign of Embedded Systems

3. Codesign of Embedded Systems
Models
Model should be
Formal => avoid ambiguity
Complete => can describe entire system
Comprehensible and easy-to-modify
Model vs. Language
We use a model to decompose a system into pieces (Model implies a way of thinking)
We generate a specification by describing these pieces in a particular language (Language is a tool for description)
Winter-Spring 2001
Codesign of Embedded Systems

4. Models: Finite-State Machines (FSM)
A set of states and a set of transitions between them
Most popular model for control systems
Formal definition
<S,I,O,f,h>
Depending on output function (h)
Mealy machine / Moore machine
Winter-Spring 2001
Codesign of Embedded Systems

5. Models: Dataflow Graph (DFG)
Most popular model for computation-intensive systems
Its basic principles
Asynchrony: all operations execute when and only when all its operands are available
Functionality: operations are functions with no side-effects => execution order is not important
Formal definition
<N,A,V,v0,f>
Winter-Spring 2001
Codesign of Embedded Systems

6. Models: FSM with Datapath (FSMD)
Both control and computation are required in most systems
FSMD is a combination of FSM and DFG models
Formal definition
<S,I,O,f,h>
f = {fC,fD}
h= {hC,hD}
Winter-Spring 2001
Codesign of Embedded Systems

7. Models: FSM with Datapath (cont’d)
Neither FSM nor FSMD are suitable for complex systems
Concurrency
Explosion in states
Hierarchy
Explosion in arcs
Winter-Spring 2001
Codesign of Embedded Systems

8. Models: Hierarchical Concurrent FSMs
Extension of FSM, supporting concurrency and hierarchy
Like FSM: sets of states and transitions
Unlike FSM: each state can consist of concurrent substates
Transitions can be structured or unstructured
An example language: Statecharts
Winter-Spring 2001
Codesign of Embedded Systems

9. Models: Programming Languages
Heterogeneous model
support data, and control modeling
Major PL types
Imperative (C, Pascal)
Control-driven model of execution
Declarative
Demand-driven / Pattern-driven model of execution
Winter-Spring 2001
Codesign of Embedded Systems

10. Models: Programming Lang. (cont’d)
Declarative languages
No explicit order of execution
Focus on defining target of the computation through a set of functions of logic rules
Imperative Languages
Variety of data-structures
Support hierarchy (functions of procedures)
Support control-flow
Well-suited for modeling an algorithm
Winter-Spring 2001
Codesign of Embedded Systems

11. Models: Programming Lang. (cont’d)
Main disadvantage
Do not explicitly model system states
Winter-Spring 2001
Codesign of Embedded Systems

12. Models: Program-State Machines
Combination of HCFSM with PL
Consists of a hierarchy of Program-states
Program-states
Leaf / composite program-states
Composite program-state
concurrent / sequential program-substates
Sequential program-substates
Transition-on-Completion (TOC) arc / Transition-immediately (TI) arc
Winter-Spring 2001
Codesign of Embedded Systems

13. Codesign of Embedded Systems
What we learned today
We use Models to decompose systems into pieces, then use Languages to generate a specification of those pieces.
FSM, DFG, FSMD, HCFSM, PL, PSM, ...
Winter-Spring 2001
Codesign of Embedded Systems

14. Complementary notes: Extra classes
“Compiler Design Short Course” by Gh. Jaberi-Pur
Date-Time: Thursday, Esfand 18th, 9-12 o’clock
Place:
“HW Synthesis Techniques Seminar” by S. Safari
Date-Time: Saturday, Esfand 20th, 13-14:30
Place
“HW design using RenoirTM workshop” by A. Ganjei
Date-Time:
Winter-Spring 2001
Codesign of Embedded Systems

15. Complementary notes (cont’d)
Assignment 1.c becomes optional
Course webpage is ready
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Project
Choose and announce your partner for the final project
Winter-Spring 2001
Codesign of Embedded Systems