Reference MVI56-BDW
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ControlLogix Platform
BARDAC Drive Web Interface
ProSoft Technology, Inc.
Page 59 of 82
September 4, 2008
The following illustration shows the data transfer method used to move data
between the ControlLogix processor, the MVI56-BDW module and the network.
All data transferred between the module and the processor over the backplane is
through the input and output images. Ladder logic must be written in the
ControlLogix processor to interface the input and output image data with data
defined in the Controller Tags. All data used by the module is stored in its internal
database. The following illustration shows the layout of the module's internal
database:
Module's Internal Database Structure
5000 registers for user data
0
Register Data
4999
Data contained in this database is paged through the input and output images by
coordination of the ControlLogix ladder logic and the MVI56-BDW module's
program. Up to 248 words of data can be transferred from the module to the
processor at a time. Up to 247 words of data can be transferred from the
processor to the module. Each image has a defined structure depending on the
data content and the function of the data transfer. The module uses the following
block numbers:
