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Rockwell Automation Publication 35-UM001A-EN-P - May 2022
Chapter 6 Safety Functions
Figure 35 - Hardwired STO - Signal Switching Device
Figure 36 - Normal Operation
Hardwired STO Fault Operation
Both Safe Torque Off safety inputs must turn off together, otherwise a
Hardwired Discrepancy (102) STO fault
occurs, even if the first safety input gets
turned on again. All hardwired inputs must be set to zero for 1 ms, for the fault
to be cleared.
If both input pairs become energized (SI0 or SI1, and SI2 or SI3), a Both Pairs
Active (105) STO Fault type will occur. All inputs must be set to zero for 1 ms for
the fault to be cleared.
Letter
Description
A
Set Safety Input SI0 = 0 volts
B
Set Safety Input SI1 = 0 volts within 0.9 seconds
C
Set Safety Input SI0 = 24 volts
D
Set Safety Input SI1 = 24 volts within 0.9 seconds
2
3
5
4
1
OSSD1
OSSD2
24V DC
-
+
Pin 1: Test Output 1
Pin 2: Safety Input 3
Pin 3: Input Common
Pin 4: Safety Input 2
Pin 5: Test Output 0
Light Curtain
or Safety Mat
A
C
D
B
0 .9
0 .9
24V
24V
8 = Waiting
51 = Wait w Trq
51 = Wait w Trq
No Fault
Disable Torque
Torque Disabled
(Safety Input) Si0
(Safety Input) Si1
Safety State
STO Fault
STO Active
Torque Disabled
