Hardware reference guide

CPU Modules
35013379 02 October 2007 221
Front Panel Slide
Switch
The slide switch, located on the front of the CPU, is used to select the comm
parameter settings for the Modbus (RS232) ports. Three options are available.
1. Setting the switch to the top position assigns ASCII functionality to the port.
2. Setting the switch to the middle position assigns remote terminal unit (RTU)
functionality to the port.
3. Setting the switch to the bottom position lets you assign comm parameters to the
port in software.
Slide switch::
The following table shows the ASCII comm port parameters.
The following table shows the RTU comm port parameters. The comm parameters
are set and cannot be changed.
Note: The CPU hardware defaults to bridge mode when the front panel switch is
set to RTU or ASCII mode. When networking controllers, a panel device connected
to the CPU Modbus port can communicate with the controller to which it is
connected, as well as log into any nodes on the Modbus Plus network.
ASCII Comm Port Parameters
Baud 2,400
Parity Even
Data Bits 7
Stop Bits 1
Device Address Rear panel rotary switch setting
RTU Comm Port Parameters
Baud 9,600
Parity Even
Data Bits 8
Stop Bits 1
Device Address Rear panel rotary switch setting
RTU
mem
ASCII
This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com