CS452 - Real-Time Programming - Fall 2009

Lecture 18 - Serial Task Structure

Reminders

Implementation

When service is required

Transmitting

Receiving

1. Getting started
   • Clear any junk from FIFO
   • Turn on receiver
   • Enable Receive interrupt
2. Receive interrupt
   • Check errors
   • Read a byte from data register

Practical Details

The Model/View/Controller Design Pattern

      /    View    \
Client              Model
      \ Controller /

In this picture

• Client
• Model
• View
• Controller

How many servers and notifiers?

How should we handle a terminal?

Issues

1. Line editing
   • undefined intermediate states
   • well-defined trigger
2. Echo

   Either

   • one server per channel,
   • passing characters from one notifier to the other

   Or

   • courier connecting receive server to transmit server
   • What characteristics does the terminal have? termcap follies

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

Task Structure for Serial IO

Servers and Attendent Tasks

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