Mitsubishi Electric WS0-CPU0 Operating Manual page 216

Chapter 9
Note
Table 94:
Conditions for Override
required and Override
possible
Figure 198:
Logic diagram for Override
and Override required
Note
ATTENTION
213
Logic programming – Function blocks
A reset button can also be suitable for the override function. Check the requirements
of your application in order to ensure that the safety-relevant logic fulfils the
requirements of the local, regional, national and international regulations.
Table 94 provides information about the Override required output and when Override
is possible under the shown conditions and when not.
At least one
Muting
muting sensor
status
is High
0 No
0 No
0 Yes
0 Yes
1 No
1 No
1 Yes
1 Yes
Figure 198 shows an example sequence for Override and Override required.
t has to be equal to or greater than the minimum override pulse time (100 ms or
high
350 ms), but less than or equal to 3 s. If t
pulse time or greater than 3 s, the Override input is ignored.
If you use Override, check whether the system is in a safe state!
The Override function is used to activate the safety output (i.e. the Enable output) of
the muting function block although the safety device (e.g. a safety light curtain) signals
that a dangerous state may exist. The Override input should only be used when the
hazardous area has been checked visually and nobody is in the hazardous area or
has access to the hazardous area while the Override input is being used.
Ensure that the transitions of the signals for Override fulfill the requirements of
the safety standards and regulations!
In case of a short-circuit to High (to 24 V DC) at a physical input, the evaluated signal
can have a pulse when the signal is reset due to the short-circuit detection. If such a
pulse can result in a dangerous state in the machine, the following points have to be
observed:
 Ensure protected cable laying for the signal line (due to cross-circuiting to other
signal lines).
 No short-circuit detection, i.e. do not reference to test outputs.
OSSDs of the Override
ESPE are High required output
0 No
1 No
0 Pulses at 2 Hz
1 No
0 No
1 No
0 No
1 No
is shorter than the minimum override
high
Override possible
No
No
Yes, if the maximum
permissible number of
override cycles is not
exceeded.
No
No
No
No
No