ProSoft Technology MVI69L-MBTCP - Manual (Page 69)

MVI69L-MBTCP ♦ CompactLogix Platform Backplane Data Exchange
Communication Module User Manual
ProSoft Technology, Inc. Page 69 of 152
January 6, 2014
All data transferred between the module and the processor over the backplane is
through the input and output images. Ladder logic is needed in the
CompactLogix 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. This database is defined as virtual MBTCP data tables with addresses
from 0 to 239 each.
4.2 Normal Data Transfer
Normal dat a transfer includes the paging of the user data found in the module’s
internal database and the status data. These data are transferred through read
(input image) and write (output image) blocks. The following topics describe the
structure and function of each block.
4.2.1 Write Block: Request from the Processor to the Module
These blocks of data transfer information from the processor to the module. The
structure of the output image used to transfer this data is shown below:
Offset Description Length (words)
0 Write Block ID 1
1 to 240 Write Data 240
The Write Block ID is an index value used to determine the location in the
module’s database where the data will be placed.
4.2.2 Read Block: Response from the Module to the Processor
These blocks of data transfer information from the module to the processor. The
structure of the input image used to transfer this data is shown below:
Offset Description Length (words)
0 Read Block ID 1
1 Write Block ID 1
2 to 241 Read Data 240