Chapter 9
196
Logic programming – Function blocks
Function test
In some applications, safeguarding devices require cyclic physical testing in order to
verify that the device continues to operate properly.
If the Safety gate monitoring function block is configured with the Function test
required parameter, the input signal(s) must change once per machine cycle in a way
that no enable condition exists anymore and back (e.g. as a result of opening and
closing of a safety gate).
Typically the
Function test request
input is connected to the machine cycle contact.
If according to the configuration a function test is required, this has to be performed
under the following conditions:
after the MELSEC-WS safety controller has changed from the Stop state to the Run
state, and
after each rising edge (Low to High) at the
Function test request
input.
This is indicated by a High signal at the
Function test required
output. The
Function
test required
output changes back to Low, if a signal sequence occurs at the inputs
that causes the
Enable
output to change from Low to High, before the next rising
edge at the
Function test request
input occurs.
The
Function test error
output becomes High and the
Enable
output becomes Low,
if the next machine cycle starts before a function test has been performed, i.e. if the
Function test required
output is still High and another rising edge (Low to High) at
the
Function test request
input occurs.
The
Function test error
output changes back to Low, if a signal sequence occurs at
the inputs that causes the
Enable
output to change from Low to High.
Sequence/timing diagrams
Figure 183:
Sequence/timing diagram
for the Safety gate
monitoring function block,
Category 2, single-channel
with function test
Figure 184:
Sequence/timing diagram
for the Safety gate
monitoring function block,
Category 4, dual-channel
equivalent (1 pair) without
function test
Summary of Contents for SW1DNN-WS0ADR-B
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