1 INTRODUCTION

In a modern digital drive, adjustments such as PID gains and acceleration ramp times are software settings rather than the potentiometers and DIP switches found in their analogue predecessors. To permit adjustment of these software parameters, most drives provide a human-machine interface (HMI) consisting of an onboard display and buttons. Users manipulate the buttons to scroll to the parameter of interest and to alter its value. The problem is that many sophisticated drives may have several hundred parameters and the built-in HMI system can be cumbersome to use. Compounding this problem is the fact that modern automation applications usually involve multiple drives working in unison with each other. A field engineer may be faced with the daunting task of setting up the parameters for thirty drives, each one having over four-hundred parameters.

To address this challenge, most modern digital drives have a built-in communications port using the RS-232 or RS-485 serial standard. There are two principal reasons for the inclusion of a communications port on a digital drive: set up of the drive's parameters and real-time control of a number of drives in an automation application.