BECKHOFF EL6900-FB - Manual (Page 37)

Function blocks
Function blocks for TwinSAFE logic terminals 35
3.5 The MON function block
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 used as normally closed contact (Break contact - 0 requests the safe state) or
normally open contact (Make contact - 1 request the safe state). The first output (MonOut) goes
immediately, and the second one (MonDelOut) after a configurable time delay, into the safe state "0",
once an input requests the safe state. Several immediate (MonOut) or delayed switch-off (MonDelOut)
outputs can be realized with only one FB MON, due to the linking possibility of the FB output with several
outputs.
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 realized as normally closed contacts (Break contact) or
normally open contacts (Make contact).
The FB restart input can be activated. The 0->1->0 signal sequence must be detected on the restart
input, in case of an active restart, before the safe state of the outputs is exited. In case of an inactive
restart the safe state is exited once the MonIn or Secure inputs no longer request the safe state.
Figure 3-9: MON function block
In addition, a feedback loop can be activated for each output, whereby the MonOut output is fed back to
the EDM1 input and the MonDelOut output is fed back to the EDM2 input, using an external circuit. Die
EDM-inputs are tested once the safe state should be exited. The FB MON goes into error state in the
case of activated restart and sets the output error to 1, when the EDM inputs don't have the "1" signal
state. The FB MON remains in the safe state in the case of deactivated restart, when the EDM inputs
don't have the "1" signal state at the restart moment. An EDM error can therefore only be detected, when
the manual restart is active. The error state can only be exited again by a 0->1->0 signal sequence on the