Allen-Bradley 1756-L6 Series, Reference Manual, Page: 62 / 134

62 Rockwell Automation Publication 1756-RM001I-EN-P - May 2012
Chapter 6 FLEX I/O Modules
• The same controller must own both modules.
• Monitor the network status bits for the associated module and ensure that
appropriate action is invoked via the application logic by these status bits.
Wiring FLEX I/O Digital Input Modules
The wiring diagrams in Figure 31 show two methods of wiring the digital input
module. In either case, you must determine whether the use of 1 or 2 sensors is
appropriate to fulfill SIL2 requirements.
Figure 31 - ControlLogix Digital Input Module Wiring
Application logic can compare input values or states for concurrence.
Figure 32 - Compare Input Values
The user program must also contain rungs to annunciate a fault in the event of a
sustained miscompare between two points.
Figure 33 - Annunciate a Fault
The control, diagnostics and alarming functions must be performed in sequence.
Input 1 Input 2
Input
COM
+24V
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0
24VDC SINK INPUT
1794-IB16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0
24VDC SINK INPUT
1794-IB16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0
24VDC SINK INPUT
1794-IB16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0
24VDC SINK INPUT
1794-IB16
Input
COM
+24V
Input 1 Input 2
SIL2 SENSOR
SENSOR
SENSOR
+24V dc
Optional relay contact
to switch line voltage
for periodic automated
testing
43366
One-Sensor Wiring Example
Two-Sensor Wiring Example
Note 1: Both sensors are monitoring the same safety application.
1
1
Input B Input A
Actuator
Input B Input A
Input B Input A
Timer
Timer preset in milliseconds to
compensate for filter time and
hardware delay differences.
Fault
Timer Done
Alarm to Operator
Fault