Backplane Data Transfer - ProSoft MVI69E-MBS User Manual

MVI69E-MBS Backplane Data Exchange
User Manual
4.2

Backplane Data Transfer

The MVI69E-MBS module communicates directly over the CompactLogix or
MicroLogix 1500-LRP backplane. Data is paged between the module and the
CompactLogix or MicroLogix 1500-LRP 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 that you define for the module and the
communication load on the module. Typical updates are in the range of 1 to 10
milliseconds per block of information.
This bi-directional data transfer is accomplished by the module filling in data in
the module's input image to send to the processor. Data in the input image is
placed in the Controller Tags in the processor by the ladder logic. The input
image for the module may be set to 62, 122, or 242 words depending on the
block transfer size parameter set in the configuration file. This data area permits
fast throughput of data between the module and the processor. Applications that
require smaller amounts of data or faster update times, such as ControlNet
networks, will benefit from smaller block transfer sizes.
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 or MicroLogix 1500-LRP processor, the MVI69E-
MBS module and the Modbus Network.
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MVI69E-MBS ♦ CompactLogix Platform
Modbus Serial Enhanced Communication Module
ProSoft Technology, Inc.
June 28, 2017