SI-Ethernet User Guide
159
Issue: 3
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7.5.3
Write consistency
Under normal conditions, cyclic data is sampled and written at the Requested Packet Interval (RPI).
However, if an option module was in the process of reading the mapped parameters while these
parameters were being written, then the data obtained may not be consistent across the entire
assembly object. If write consistency is enabled (
Out Consistency Enable
(
S.20.028
)) and a trigger
parameter specified in
Out Consistency Trigger Param
(
S.20.029
) then new data will only be written
to the drive (or option module) when the trigger parameter
Out Consistency Trigger Param
(
S.20.029
) contains a value of zero. This trigger parameter will then be set to one after the data has
been written.
It is therefore possible, by controlling the trigger parameters, that a user program in the drive or
option module can ensure that the values in the cyclic data parameters are not sampled until all
values are updated.
Whether consistency is enabled or not, data will always be consistent for an individual parameter,
i.e. all 4 bytes of a 32-bit value will be consistent.
Example
In this example, Pr
0.18.031
is set as the input trigger and Pr
0.18.032
is set as the output trigger.
The EtherNet/IP master is configured to check the values of Pr
0.20.011
and Pr
0.20.012
are equal
and write the same value to Pr
0.20.021.
The SI-Applications Plus module is configured to generate
a ramp value between -32768 and 32767 to write to Pr
0.20.011
and Pr
0.20.012
when the value of
Pr
0.20.021
is equal to the ramp value.
With the input and output consistency enabled, parameters Pr
0.20.011
and Pr
0.20.012
will be
sampled and transmitted to the EtherNet/IP master when the input trigger parameter Pr
0.18.031
is
a non-zero value, Pr
0.20.021
will be written to when the output trigger parameter Pr
0.18.032
is a
value of zero.
The parameter changes required are:
S.20.020
Input assembly object size
= 8 (bytes)
S.20.021
Output assembly object size
= 4 (bytes)
S.20.026
In Consistency Enable
= On
S.20.027
In Consistency Trigger Param
= 0.18.031
S.20.028
Out Consistency Enable
= On
S.20.029
Out Consistency Trigger Param
= 0.18.032
S.21.001
Input mapping parameter 1
= 0.20.011
S.21.002
Input mapping parameter 2
= 0.20.012
S.22.001
Output mapping parameter 1
= 0.20.021
Содержание Unidrive M600
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