Bb-electronics 485LP9R - Datasheet Manual de usuario descargar pdf

Document No. 485LP9R1712 - pg. 1/2

www.bb-elec.com [email protected] sup[email protected]

International Office: 707 Dayton Road PO Box 1040 Ottawa, IL 61350 USA 815-433-5100 Fax 433-5104

European Office: Westlink Commercial Park Oranmore Co. Galway Ireland +353 91 792444 Fax +353 91 792445

PRODUCT INFORMATION B&B ELECTRONICS

Port Powered RS-232 to RS-485 Converter

Model 485LP9R

The 485LP9R is a port-powered two-channel RS-232 to RS-485

converter. It converts TD and RD RS-232 lines to balanced RS-485 signals.

The unit can be powered from the RS-232 handshake lines, DTR and RTS.

One of these handshakes must be high (asserted) to power the unit (See Table

1). DTR must be asserted to receive data. The RS-485 driver is enabled when RTS is asserted and disabled when

RTS is disasserted. The RS-485 receiver is disabled when the driver is enabled and is enabled when the driver is

disabled.

In order to maximize the amount of power available to the RS-485 driver, the RS-232 handshake lines

are not looped back (tied together). As a result the following handshake lines will appear as disasserted (low):

CTS, DCD, and DSR. Care should be taken to insure that any software being used doesn’t require any of these

handshake lines be asserted. If existing software requires any of the handshake lines to be asserted, you can loop

back the required handshake lines in your cable.

Table 1

* NOTE: Low = disasserted and High = asserted

Connections

A typical two wire RS-485 connected is shown in Figure 1. Regardless of the system, the 485LP9R must

be connected with the proper polarity. With no data is being sent and the driver enabled, the RS-232 line should

be negative and the TD(A) should be negative with respect to TD(B).

Proper operation of any RS-485 system requires the presence of a signal return path between the signal

grounds of the equipment at each end of an interconnection. This circuit reference may be established by a third

conductor connecting the common leads of devices, or it may be provided by connections in each equipment to

an earth reference. When the circuit reference is provided by a third conductor, the connection between the signal

grounds and the third conductor should contain some resistance (e.g. 100 ohms) to limit circulating currents when

other ground connections are provided for safety.

Figure 1

Table 2 - 485LP9R Pin Outs

RTS State

DTR State

Functions Possible

(when port powering unit)

Low

none

Low

High

Receive

High

Low

Transmit

High

Transmit

1 2

DECLARATION OF CONFORMITY 2

Indice de contenidos

Pagina 1

Document No. 485LP9R1712 - pg. 1/2 www.bb-elec.com [email protected] [email protected] International Office: 707 Dayton Road PO Box 1040 Otta

Pagina 2 - DECLARATION OF CONFORMITY

Document No. 485LP9R1712 - pg. 2/2 www.bb-elec.com [email protected] [email protected] International Office: 707 Dayton Road PO Box 1040 Otta

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