Interface-based Design

Interface-based Design

Donald Chai

EE249

Outline

Orthogonalization of concerns Formalisms Interface-based Design Example Cheetah Simulator Future Inroads

Orthogonalization of Concerns

Behavior (or computation,

coordination)

Communication (or interfaces)

These two are (or should be) independent

Interface-based Design

Done all the time OSI stack Memory mapped I/O Virtual memory

Required Tools

A good formalism with which to perform: Abstraction (and hierarchy) Decomposition (and composition)

These concepts exist for both computation and communication

Formalism – Models of Computation

All models of computation specify a set of actors and a communication mechanism FSMs – synchronous composition CFSMs – event broadcast Dataflow/KPN – lossless queues CSP – rendezvous

Some models conflate communication and computation

Refinement (Abstraction-1)

1. Simple channel through which tokens are passed

2. REQ/ACK protocol• Master requests, slave

acknowledges

3. Repartition

(De)composition

Largely ignored in this paper

Consider at least three communicating processes

Design Example

What Software thread sending packets through a

hardware transmitter Asynchronous Transfer Mode (ATM)

How Communication through bus (PCI, EISA, or PI) Single byte transmission or burst mode?

Cheetah Simulator

Event driven Built with

communication platforms

Cheetah Simulator (II)

At most abstract level, channel has a simple delay

With more detail, expands in both space and time

Simulation speed varies from 7x to 175x RTL

Future Inroads

Better modeling and design exploration Can mix and match communication and behaviors

Better synthesis Allows design reuse Improves don’t care extraction Composeability

Future Inroads (II)

Verification Abstraction and Decomposition are necessary Can be used between steps in communication

platform Formal specification allows test generation