Sto Diagnostics; Figure 2-33: Sto Timing; Table 2-32: Sto Timing - Advantech Automation1 XC4 Hardware Manual

XC4 Hardware Manual

2.4.4. STO Diagnostics

Activation of STO means removing power from the XC4's STO inputs. This is typically done by pressing
the emergency stop switch. The XC4 initiates a diagnostic check every time the STO is activated after the
Diagnostic Test Delay Time has elapsed. The diagnostic check verifies that each channel has entered the
safe state. The XC4 is held in the safe state if it determines that one of the channels has not properly
entered the safe state. An open circuit or short to 24 V in either STO channel will result in this condition
(refer to Section 2.4.3.). The Status Utility screen can be used to verify the levels of the STO input signals
while trouble shooting.
In order to meet the listed SIL level, the STO circuit must be activated (power removed from both inputs)
according to the interval specified in
Table 2-32: STO Timing
Time Description
T1 STO Delay Time (STO input active to motor power off)
STO deactivated to motor power on (the software is typically
T2
configured so that the motor does not automatically re-energize).
T3 Diagnostic Test Delay Time
The software is typically configured to execute a controlled stop when the STO state is first detected. If
power is reapplied to the STO inputs before the STO Delay Time, an STO hardware shutdown will not
occur but a software stop may, depending on the width of the STO pulse. The controller will ignore STO
active pulses shorter in length than the STOPulseFilter parameter setting.
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Table 2-29.
Figure 2-33: STO Timing
2.4. Safe Torque Off Input (STO)
Value
450-550 msec
< 1 msec
550-610 msec
65