Copyright © 2010 Future Technology Devices International Limited

11

Document Reference No.: FT_000132

USB-COM485-PLUS1 Datasheet

Version 1.21

Clearance No.: FTDI# 95

3 Connections

3.1 External Connectors

3.1.1 USB

The USB-COM485-Plus1 is a downstream USB 2.0 Device. A standard USB Series “B” receptacle is

reference to USB-F-1001 to facilitate connection to an upstream USB Host or Hub.

Pin Number

Pin Type

Description

1

Power

VBUS = USB Power provided from upstream USB Host or Hub

2

Bidirectional

D– = USB data signal, negative polarity

3

Bidirectional

D+ = USB data signal, positive polarity

4

Ground

GND = USB signal ground

Shield

Case Ground

Drain = typically connected to the host PC case

Table 3.1 USB "B" Receptacle Pin-Out

3.1.2 RS485

The RS485 port is 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 DE-9P may be assigned to provide

+5VDC to an external device with a maximum current draw of 250mA once the USB-COM485-Plus1 has

been enumerated by the system.

Pin Number

Pin Type

Description

1

Input/Output

DATA- = Transmit/Receive Data, negative polarity

Pin 2 of 120R Terminating Resistor. Only Required if the USB-COM485-

PLUS1 is the first or last device in a multi-drop RS485 System, to meet

RS485 Termination Requirements.

2

Input/Output

DATA+ = Transmit/Receive Data, positive polarity

3

Input/Output

Pin 1 of 120R Terminating Resistor. Only Required if the USB-COM485-

PLUS1 is the first or last device in a multi-drop RS485 System, to meet

RS485 Termination Requirements.

4

N/A

N/A

5

Ground

GND = signal ground

6

N/A

N/A

7

N/A

N/A

8

N/A

N/A

9

Power

provide +5VDC to an external device

Table 3.2 DE-9P RS485 Pin-Out

A 120R Resistor is connected internally between pin 1 and pin 3 of the 9 way D-type connector – see

Figure 2.1