Hardware reference guide

CPU Modules
176
35013379 11/2011
Front Panel Slide Switch
The slide switch, located on the front panel of the CPU, is used to select the
communication parameter settings for the Modbus (RS-232) ports. Three positions
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.
The slide switch:
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.
Setting the slide switch to the top position assigns ASCII functionality to the port; the
following communication parameters are set and cannot be changed.
Setting the slide switch to the middle position assigns remote terminal unit (RTU)
functionality to the port; the following communication parameters are set and cannot
be changed.
ASCII Communication Port Parameters
Baud 2,400
Parity Even
Data Bits 7
Stop Bits 1
Device Address Rear panel rotary switch setting
RTU Communication Port Parameters
Baud 9,600
Parity Even
Data Bits 8
Stop Bits 1
Device Address Rear panel rotary switch setting