Allen-Bradley 1747-DCM Installation Instructions Manual page 11

Clear on Fault (SW2-3)
Clear On Fault
Yes
No
Turn the switch to the OFF position if you want the 1747-DCM to clear and hold
clear all data bits in its input image table in the event of an RIO communication
failure or when the supervisory processor enters the Program/Test/Fault mode.
Status bits will not be cleared.
Turn the switch to the ON position if you want the 1747-DCM to hold all input data
bits in their last state if an RIO communication failure occurs or when the
supervisory processor enters the Program/Test/Fault mode.
ATTENTION
!
Last Chassis (SW2-4)
Switch SW2-4 must be set to the OFF position if the 1747-DCM shares its logical
chassis with at least one other adapter and has been assigned the highest I/O group
number in that logical chassis.
Last Chassis
Yes
No
SW2-3
OFF
ON
Before setting SW2-3 to ON, make sure that holding all 1747-DCM
input bits in their last state, in the event of an RIO communication
failure, does not create an unsafe condition in the distributed SLC
processor.
SW2-4
OFF
ON
Direct Communication Module
Publication 1747-IN005B-EN-P - March 2003
11