CS452 - Real-Time Programming - Spring 2009

Lecture 18 - Serial IO: Programmer's Model

Practical Details

How many servers and notifiers?

one server two servers four servers
one

notifier

likely queue

congestion in

server

likely queue

congestion

in notifer

two

notifiers

one per channel?

one per direction?

how should they

be paired?

four

notifiers

certain queue

congestion

in server

likely queue

congestion in

server

best performance,

most tasks

How should we handle a terminal?

Issues

  1. Line editing
  2. Echo

    Either

    Or

Many other issues come up below as we consider possible task structures.


Task Structure

Servers and Attendent Tasks

Proprietor with a Notifier

Proprietor `owns' a service

Proprietor Code

Notifier Code

Notes

  1. Notifier is usually of higher priority than server
  2. When, and by whom, do interrupts get turned on in the CPU?
  3. Who coordinates hardware ownership?

Using a Courier


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