13

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This chapter presents a basic network that uses a primary/secondary protocol. A

primary node sends commands to the secondary nodes. Each secondary node

detects, reads, and responds to commands directed to it.

You can use the network as a base for designing projects using PCs and embed-

ded systems of any type, in any combination. The example code includes PC

code for the primary node and microcontroller code for the secondary nodes.



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Chapter 12 introduced the options for wiring the nodes in an RS-485 network.

Figure 13-1 shows a configuration you can use for the example network in this

chapter.

1
  8


The network can use any appropriate transceivers for half-duplex RS-485 ports,

including high-speed, low-speed, low-voltage, short-distance, and isolated com-

ponents. A PC can use an expansion card with an RS-485 interface, a