Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 15)

Installation
Chapter 2
2Ć3
CAUTION: To guard against unpredictable operation of the
PLC–3 processor, do not change the setting on any thumbwheel
switch while the 1775–KA module is powered–up.
Option Switches
Figure 2.2 shows a set of four option switches on the bottom edge of the
1775– KA module. Switches 1 and 2 are used when the PLC–3 controller
is programmed to operate in a backup configuration. Switch number 1
determines whether or not a fault in the 1775–KA module will cause the
primary PLC–3 controller to switch over to the backup PLC–3. Switch
number 2 determines whether or not the 1775–KA module will disable its
Data Highway port when the PLC–3 becomes deactive. Switch 3 is for
RS–232–C communication. Switch 4 is reserved for future use and
should always be left open (up, or off). Use Table 2.A below to determine
the appropriate switch setting:
Figure 2.2
Option Switches