18 SM-Applications Modules & Motion Processors User Guide
Issue Number: 4
Repeaters can be purchased from Control Techniques. The table below shows the part
numbers for the different repeaters available.
Please refer to the CTNet User Guide for further guidance on these points.
3.7 EIA-RS485 Connections
Please note that SM-Applications Lite, SM-Applications Lite V2 and ST Indexer do not
have these connections.
The EIA-RS485 port is available for lower-speed communications (up to 115,200bit/s).
As standard the port supports the CT-ANSI slave, Modbus-RTU master and slave, and
Modbus-ASCII master and slave protocols. Both 2 and 4-wire connections are possible.
More information on the use of the EIA-RS485 port can be found in Chapter
6 Communications on page 69.
A host controller can operate up to thirty-two EIA RS485 devices with the use of line
repeaters. Each transmitter and receiver of Control Techniques devices loads the line by
2 unit loads. Therefore in two-wire mode, each Control Techniques device loads the line
by 4 unit-loads. This means that no more than a total of seven devices can be
connected in a single group, allowing up to 4 unit-loads for the line repeater. Up to 15
devices can be connected if four-wire mode is used.
3.7.1 4 Wire EIA-RS485 Network
The diagram below shows the connections required for a 4 wire EIA-RS485 network,
using a master controller with an EIA-RS485 port. SM-Applications Modules & Motion
Processors can be configured to act as master controllers, but this requires DPL
programming to control the network.
An EIA-RS232 to EIA-RS485 converter is required to allow a standard PC serial port to
communicate with a 4 wire EIA-RS485 network.
Part
Numer
Description
4500-0033 AI3-485X - Rev A
4500-0083 AI3-485X-CT - Rev D (Port 1), Rev A (Ports 2 and 3)
4500-0082 AI3-CT - Rev D
4500-0032 AI2-485X/FOG-ST - Rev A (Fibre Optic)
4500-0081 AI2-CT/FOG-ST - Rev D (Fibre-Optic)
0V /Rx Rx /Tx Tx
12345
SM-Applications Module
Slave
5 4 3 2 1
9 8 7 6
UD70, MD29, Unidrive, Mentor
II
Slave
120 0.25W
termination resistors
0V /Rx Rx /Tx Tx
12345
Master
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