Black-box IC171C Bedienungsanleitung PDF herunterladen (Seite 10)

CHAPTER 2: Introduction

This interface is ideal for multi-drop or network environments. The RS-485

tri-state driver (not dual-state) will allow the electrical presence of the driver

to be removed from the line. The driver is in a tri-state or high-impedance

condition when not active. Only one driver may be active at a time and the

other driver(s) must be tri-stated.

Some communication software packages refer to RS-485 as RTS enable or

RTS block mode transfer.

RS-485 can be cabled in two ways, 2- and 4-wire mode. Two-wire mode does

not allow for full-duplex communication. It requires that data be transferred

in only one direction at a time and the two transmit pins be connected to the

two receive pins (Tx+ to Rx+ and Tx- to Rx-). Four-wire mode will allow full-

duplex data transfers. RS-485 does not define a connector pin-out, modem

control signals, or a physical connector.

Figure 2-2. RS-485 Two-Wire Connection.

TX+

TX-

RX+

RX-

RX+

RX-

TX+

TX-

TX+

TX-

RX+

RX-

RX+

RX-

TX+

TX-

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Black-box IC171C Bedienungsanleitung Seite 10