Function blocks
Function blocks for TwinSAFE logic components 55
3.5 The function block MON
3.5.1 Functional description
A safety door circuit with up to four inputs (MonIn(x)) can be realized with the FB MON for example. Each
of the four inputs can be parameterized as break contact (0 requests the safe state) or make contact (1
request the safe state).
When an input requests the safe state, the MonOut output immediately switches to the safe state ("0")
and the MonDelOut output switches after a configurable delay. Each FB output can be linked to several
outputs. Therefore, several outputs that switch off immediately (MonOut) or with a delay (MonDelOut) can
be realized with just one FB MON.
In addition there are two Secure inputs, with which the request of the safe state can be bypassed through
the MonIn inputs. The Secure inputs can also be parameterized as break contacts or as make contacts.
The FB restart input can be activated. To exit the safe state of the outputs, a rising and falling edge must
be detected at the Restart input when Restart is active (see also chapter 3.5.4 Restart behavior). No time
monitoring of the restart signal takes place. In case of an inactive restart the safe state is exited once the
MonIn or Secure inputs no longer request the safe state.
Figure 3-18: MON function block
A feedback loop can be activated for both outputs. The output MonOut is returned to the input EDM1 and
the output MonDelOut to the input EDM2 through external wiring. The EDM inputs are checked when the
FB changes to the START state (6) (see 3.5.4 Restart behavior).
If Restart is enabled, the FB MON assumes the error state (FB Error) and sets the Error output to 1 if the
EDM inputs do not have the signal state TRUE. The error state can only be exited through
acknowledgement via the ERR_ACK input of the associated TwinSAFE group.
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