Black Box RS-485 Manual De Usuario

RS-485
RS-485 is backward-compatible with RS-422; however, it is optimized for
multidrop applications. The output of the RS-422/485 driver is capable of
being active (enabled) or tri-state (disabled). This capability allows multiple
ports to be connected in a multidrop bus and selectively polled. Half-duplex
two-wire communications are possible by connecting TX+ to RX+ and TX- to
RX- in your cable connector. The enable to the driver is connected to the
UART Request To Send (RTS) line for RS-485 communications. This allows
the RS-485 driver to be tri-stated (disabled) when inactive on a multidrop
polled network. The software that you are using must “know how” to enable
the driver when it is answering a poll. Failure to set this jumper correctly can
cause transmitter contention problems, preventing operation by any nodes on
the network.

The table below shows the connector pinouts for ports J1 (port 1) and J2
(port 2) on the Interface while using RS-422/485.

4

Transmit Data Pos. (TX+)

Output RS-422

3

Transmit Data Neg. (TX-)

Output RS-422

6

Req. To Send Pos. (RTS+)

Output RS-422

7

Req. To Send Neg. (RTS-)

Output RS-422

5

Ground (GND)

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1

Receive Data Pos. (RX+)

Input RS-422

2

Receive Data Neg. (RX-)

Input RS-422

9

Clear To Send Pos. (CTS+)

Input RS-422

8

Clear To Send Neg. (CTS-)

Input RS-422