Rockwell Automation 1758-RTU202 DataSite Hardware User Manual User Manual
Page 40
Publication 1758-UM001D-EN-P - June 2011
40 Wiring the Controller
RS485 Two-wire Connection Mode
When the RS485 port uses a 2-bit fixed connecting terminal to connect with
the RS485 network, it runs primarily in the two-wire mode.
RS485 Termination
The following table describes each termination signal of the RS485 port.
When the two-wire connection is made, a pair of wires is used for sending and
receiving data.
RS485 Field Wiring—Two-wire Mode
Pin Assignments for RS485 Connector
Pin
Function
Description
17
Data+
The terminal is the differential input/output positive
terminal.
18
Data-
The terminal is the differential input/output negative
terminal.
Data+ Data-
17
18
44699
Master
Station
First station in network
requires terminations
Last station in network
requires terminations
RS-485 network
4000 feet (1200m)
maximum length
D
D
Slave
Station
D
D
Slave
Station
D
D
44700