Safety Signals Comparison; Re-Start After Error - Mitsubishi Electric MELSEC Q Series Programming Manual

2 SAFETY OBSERVATION FUNCTION

2.3 Safety Signals Comparison

2.3.1 Re-start after error

The input/output signals on Motion CPU side and PLC CPU side are compared.
If the mismatch status of input/output signal exceeds the setting allowance time,
"Safety observation error (error code: 20)" occurs, and the shut-off signal is turned
OFF.
When each CPU detects a signal comparison error, the shut-off signal is turned OFF
and the mismatch status is reported to the other CPU at the same time. Set the
mismatch allowance time in consideration of the time lag of signal input and signal
reading for each CPU.
Safety signal
Motion CPU side
Safety signal
PLC CPU side
Comparison mismatch
Motion CPU side
Comparison mismatch
PLC CPU side
Shut-off signal (Y A)
Motion CPU side
Shut-off signal (Y A)
PLC CPU side
When a signal comparison error occurs, turn ON the system's power supply after
checking the wiring where the input error occurred and eliminating the error cause.
Safety observation warning (SM24) is turned ON and "Safety comparison warning
(error code: 11)" occurs after power ON. Turn ON/OFF the error signal during signal
comparison. Release the warning by the reset operation (PLC ready flag (M2000) OFF
to ON or Motion error detection flag ((M2039) ON to OFF) after confirming the signal
input.
POINTS
(1) Continuous operation with "Safety observation warning (error code: 11)" may
damage the safety observation function due to accumulated errors. Safety
observation warning (SM24) should be OFF when starting the machine
operation after power ON.
X
SM24
Startup Safety
instruc observation
tion warning
(2) When "Safety observation warning (error code: 11)" occurs, make sure to
confirm that the signal is input properly by turning the error signal ON/OFF
during the signal comparison. And, inform that this signal confirmation is
required through a man-machine I/F such as the indicator.
When mismatch time is within
allowance time an error won't occur.
Y A
Shutoff
signal
2 - 7
Error will occur if the
mismatch time exceeds
the allowance time
Mismatch
allowance time
Shut-off signal will still be OFF even when
the signals match after error detection.
M
Machine
operation
starts