Copyright © 2010 Future Technology Devices International Limited

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Document Reference No.: FT_000136

USB-COM485-PLUS2 Datasheet

Version 1.3

Clearance No.: FTDI#104

3.1.2 RS485

The RS485 ports are configured as Data Terminal Equipment (DTE), with a 9-contact D-Sub Pin

connector. Pin assignments are according to TIA/EIA-485. In addition, pin9 of DB9 provides +5VDC to

an external device with a maximum current draw of 450mA once the USB-COM485-PLUS2 has been

enumerated by the system. Both D-type connectors have a similar connection as described in Table 3.2.

Pin Number

Pin Type

Description

1

Input/Output

DATA-

Pin 2 of 120R Terminating Resistor. Only Required if the USB-

COM485-PLUS2 is the first or last device in a multi-drop RS485

System, to meet RS485 Termination Requirements.

2

Input/Output

DATA+

3

Input

Pin 1 of 120R Terminating Resistor. Only Required if the USB-

COM485-PLUS2 is the first or last device in a multi-drop RS485

System, to meet RS485 Termination Requirements.

4

N/A

N/A

5

GND = signal ground

GND

6

N/A

N/A

7

Input

Pin 7 of the local echo control. Connect to pin 8 of the echo

control to disable local echo. Default is that local echo is

enabled.

8

Output

Connect to pin 7 of the echo control to disable local echo.

Default is that local echo is enabled.

9

PWR = +5V DC output

PWR

Table 3.2 – DE-9P RS485 Pin-Out