Chapter 9
192
Logic programming – Function blocks
9.9.4 Emergency stop
Function block diagram
General description
The Emergency stop function block allows the implementation of an emergency stop
function with an emergency stop pushbutton.
If a corresponding dual-channel input element is configured in the hardware
configuration of the Setting and Monitoring Tool, this function block is no longer
required in the logic since the pre-evaluation is then carried out directly on the safety
I/O module (e.g. WS0-XTDI or WS0-XTIO module). But if the Fault present output is
required for further processing, the function block can be used. To this purpose the
two input signals have to be configured as single-channel signals and applied to the
inputs of the function block.
In the case of emergency stop pushbuttons, a Reset and/or Restart function block has
to take over the processing of the reset/restart conditions for the safety chain when the
Enable output is set to Low. This can also be necessary for emergency stop
pushbuttons with a combined push-/pull-to-unlatch mechanism.
Figure 178:
Sequence/timing diagram
for the Safety gate
monitoring function block,
Category 4, dual-channel
equivalent (2 pairs) without
function test
Figure 179:
Function block diagram for
the Emergency stop function
block
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