Specifications

Chapter 1 - Overview RS-422 And RS-485 Applications Ebook
Page 7 of 137 Manual Documentation Number: <DocNumber>
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operate over longer distances at higher bit rates than links using RS-
232.
RS-422's capabilities make it a good choice for extending the distance
and speed of point-to-point connections. In situations where data must
be communicated over long distances and through electrically noisy
areas, RS-422 provides a higher reliability replacement for standards
such as RS-232 .
Figure 1: RS-422 Point-to-Point Link
RS-422 also makes it possible to create point-to-multipoint
connections. In a point-to-multipoint arrangement the node originating
the data (master) can broadcast data to several (slave) nodes at once.
However, for the master to receive data back from each slave, RS-485
devices are required.
RS-485 can be used in two and four-wire networked systems. The tri-
state capabilities of RS-485 transmitters enable multiple transceivers
(transmitter/receiver pairs) to be connected to a two-wire multidrop
bus. Alternately, a four-wire system can be used in which the master
node driver is connected to all slave receivers and all slave drivers are
connected to the master receiver.
Figure 2: RS-485 Daisy Chain Network