Advantech PCI-1602 Spécifications télécharger pdf (Page 78)

74 PCI-Comm Card Series User's Manual

RS-485 signal wiring

The RS-485 standard supports half-duplex communication. This

means that just two wires are needed to both transmit and receive

data. Handshaking signals (such as RTS, Request To Send) are

normally used to control the direction of the data flow and to switch

the transmission accordingly. In RS-485 mode, the PCI-1601/1602/

1612 automatically senses the direction of the data flow and switches

the transmission direction — no handshaking is necessary. This

means a user can build an RS-485 network with just two wires. This

RS-485 control is completely transparent to the user. The Software

written for half duplex RS-232 works without the need for any

modification.

RS-485 wiring topology

D.T.E

RS-485

Transceiver

D.T.E

RS-485

Transceiver

D.T.E

RS-485

Transceiver

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Advantech PCI-1602 Spécifications Page 78