Mitsubishi Electric MELSEC Q Series Programming Manual page 78

2 SAFETY OBSERVATION FUNCTION
Output off check not complete
(SM27)
Safety signal output off check
(SM28)
Servo ready status
All output signal of
safety sugnal module
Feedback input signals of
the output signals
(2) Output off check function every 24 hours
When all output signals have not stayed OFF for 24 hours, output off check
incomplete signal is turned ON. Turn ON output off check signal in user program.
When "Output off check signal" is turned ON, the following will be carried out.
(a) The Motion CPU is in emergency stop status and all-axis servo ready are
turned OFF only when the forced stop is assigned to the M flag.
(b) All output signals from the safety signal module are turned OFF.
(c) Confirm that the feedback signals are turned OFF within a certain period of
time.
(d) Return the output to the original status.
When the output off check is completed, "Output off check incomplete signal" is
turned OFF. "Safety observation error" occurs if output off signals are not
confirmed. If an error is detected during the PLC CPU side output check, "Safety
observation error (error code: 50)" occurs. For Motion CPU side, "Safety
observation error (error code: 51)" occurs.
When all output signals are confirmed as OFF, the output off check is complete.
When "Output off check incomplete signal" is output, make sure to execute the
output off check using the output off check function.
The sequence program below is additionally required to execute the output off
check automatically when output off check incomplete signal is turned ON. Output
off check enable signal below is a signal that indicates the machine remains safe
even when all outputs are turned OFF.
M SM27
Output
Output
off check
off check
possible
incomplete
Create the user safety sequence program so that an operator cannot touch the
moving parts when "Output off check not complete signal" is ON (e.g., Disable the
door lock, shut the power down, etc.). During the output off check, the sequence
scan time becomes longer (not an error).
If all output are not turned OFF for 24 hours, the check will be turned ON.
When output off check not complete,
output off check execute.
When output off check execute, all-axis servo ready is turned OFF.
All output signals turned OFF.
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SM28
Output
off check