ProSoft Technology MVI69L-MBTCP - Manual (Page 68)

Backplane Data Exchange MVI69L-MBTCP ♦ CompactLogix Platform
User Manual Communication Module
Page 68 of 152 ProSoft Technology, Inc.
January 6, 2014
4.1 Backplane Data Transfer
The MVI69L-MBTCP module communicates directly over the CompactLogix
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 per block of information.
This bi-directional transference of data 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 is 242 words. This 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 is 241.
The following illustration shows the data transfer method used to move data
between the CompactLogix processor, the MVI69L-MBTCP module and the
Modbus Network.