Knowledge Base / Rockwell In-chassis / ControlLogix / MVI56 Series / MVI56-MCM

How do I increase my ReadData array for an MVI56-MCM module?

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The sample ladder file must be modified in 3 locations. Before
making these changes, save the work you have already done,
as changing this array, may erase any values in your MCM array.1. "MCMmoduledef" user defined object. open the user-defined
object for "mcmmoduledef" object. Within this object, there is
the tag readdata. The current data type is shown as int[600],
this will need to be changed to int[2000]. This will give you
a total of 2000 elements within the mcm.readdata tag. Once you
have made the change click apply.note: You will get the following warning: "data type referenced
by one or more tags. changes to data type member(s) could result
in loss or truncation of data, e.g. type conversions, decreased
array dimensions. Change data type?". This may erase your data
values, make sure you have saved a copy of this file before making
this change.2. Within the readdata ladder file, rung 2, there is a lim statement
that looks for mcm.bp.lastread to be between 1 and 3. For 2000
words of readdata we will need this to be between 1 and 10.The module pages data in blocks of 200 words. The first block has
a block index of 1, and contains the first 200 words of data
from the MVI module. Each subsequent block will have another 200
blocks of data.3. Finally in the controller tags, mcm.moddef.readregcnt, this
will need to be set to a value of 2000. This will tell the module
to pass 2000 words of data to the processor, or 10 blocks of data.Once this change has been made, a warmboot or coldboot bit will
need to be toggled in order to send this change to the module

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