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Use a structured design method (e.g., state diagrams) to develop a complete ladder logic program to perform the task.
6. A PLC-5 is connected to a scale that measures weights and then sends an ASCII string. The string format is ‘XXXX.XX’. So a weight of 29.9 grams would result in a string of ‘0029.90’. The PLC is to read the string and then check to see if the weight is between 18.23 and 18.95 grams. If it is not then an error output light should be set until a reset button is pushed.

plc serial -27.19 plc network -28.1

28. NETWORKING

Topics:

* Networks; topology, OSI model, hardware and design issues
* Network types; Devicenet, CANbus, Controlnet, Ethernet, and DH+
* Design case

Objectives:

* To understand network types and related issues
* Be able to network using Devicenet, Ethernet and DH+

28.1 INTRODUCTION

A computer with a single network interface can communicate with many other computers. This economy and flexibility has made networks the interface of choice, eclipsing point-to-point methods such as RS-232. Typical advantages of networks include resource sharing and ease of communication. But, networks do require more knowledge and understanding.

Small networks are often called Local Area Networks (LANs). These may connect a few hundred computers within a distance of hundreds of meters.

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