7.1 Introduction

This chapter discusses issues pertaining to and procedures involved in developing an application using the AG Access library. The topics discussed are:

• Driver Initialization

• Port Initialization

• Command and Event Processing

• Execution Environment

• Port Multiplexing

• Programming Models

• Error Codes and Handlers

• Parameter Management

This chapter builds on the concepts and terminology laid down in Chapter 2, which identifies and defines the major architectural components of AG Access. In this chapter, the issues relevant to building systems using those components are discussed.

Specifically, this chapter focuses on the interaction between the application program, the AG Access library, and the operating system. It is assumed that the reader is familiar with operating system concepts such as processes, threads, device drivers, and reentrancy.

Application development with AG Access is based on the following principles:

• The application performs telephony operations on ports which are defined in Section 2.5, Ports.

• The application must open the AG driver in order to access the ports on AG boards.

• AG Access allows ports to be multiplexed between the application and the AG driver; i.e., more than one port may be accessed from a single open driver instance.

• AG Access is a dynamic linked library and is serially reentrant for multi- threaded operating systems (i.e., semaphore protected).

To use AG Access, execute the following initialization sequence:

1. Open the AG driver to gain access to the AG boards.

2. Open one or more ports using the driver instance in Step 1.

3. Continuously wait for events from the port(s). When an event occurs, retrieve it from the driver and process it.

These steps are described in the next three sections.

Copyright 1996 Natural MicroSystems, Inc. All Rights Reserved.