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6-18
Safe Torque Off
890CS Common Bus Supply - Frames B & D; 890CD Common Bus Drive and 890SD Standalone Drive - Frames E & F
Pulsed Inputs
Some safety equipment, e.g. safety PLCs, regularly pulse the two STO inputs independently in order to detect a
short circuit between them. This is commonly known as OSSD (Output Signal Switch Device). The 890STO
inputs are immune to such pulses when these are less than 2ms in width. The product will not react to such pulses
and therefore will not inadvertently invoke the STO function.
States:
1
Both inputs are low. STO prevents the drive from starting. User output is ON. This is the “safe torque off”
state of the drive.
2
Both inputs are high, but regularly pulse low independently. External equipment can thus detect a short
circuit between the two STO user inputs. Each input must remain low for 6ms (typical) before the 890
reacts to it.
2 1
<2ms <2ms typ 6ms
Channel A: X11/01
Channel B: X11/03
Output: X11/05, X11/06
STATE
24V
0V
24V
0V
ON
OFF