ProSoft Technology MVI69-HART - Manual (Page 86)

Reference MVI69-HART ♦ CompactLogix Platform
User Manual HART Multi-drop Master Communication Module
Page 86 of 169 ProSoft Technology, Inc.
March 29, 2012
5.2.2 Backplane Data Transfer
The MVI69-HART module communicates directly over the CompactLogix or
MicroLogix backplane. Data is paged between the module and the CompactLogix
processor across the backplane using the module's input and output images. The
update frequency of the images is determined by the scheduled scan rate
defined by the user for the module and the communication load on the module.
Typical updates are in the range of 1 to 10 milliseconds.
Data received by the master drivers is placed in the module's input image. This
data is processed by the ladder logic in the CompactLogix processor. The input
image for the module varies depending on the block size specified in the
configuration file. This large data area permits fast throughput of data between
the module and the processor.
The processor inserts data to the module's output image to transfer to the
module. The module's program extracts the data and places it in the module's
internal database. The output image for the module may be set to 61, 121, or 241
words depending on the block transfer size parameter set in the configuration
file.
The following illustration shows the data transfer method used to move data
between the CompactLogix processor, the MVI69-HART module and the HART
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
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.
As blocks are transferred between the module and the processor, each block
contains block identification codes that define the content or function of the block
of data transferred.