ProSoft Technology MVI56-103M - Manual (Page 98)

Reference MVI56-103M ♦ ControlLogix Platform
User Manual IEC 60870-5-103 Master Communication Module
Page 98 of 152 ProSoft Technology, Inc.
February 22, 2013
5.2.3 Backplane Data Transfer
The MVI56-103M module communicates directly over the ControlLogix
backplane. Data travels between the module and the ControlLogix processor
across the backplane using the module's input and output images. The update
frequency of the data is determined by the 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 ControlLogix processor. The input
image for the module is set to 500 bytes. This large data area permits fast
throughput of data between the module and the processor.
The processor inserts data in the module's output image to transfer to the
module. The module's program extracts the data and transmits the data out to
the Master driver to the serial network. Additionally, the ControlLogix processor
can send special control blocks to the module to instruct it to perform a special
task. The output image for the module is set to 496 bytes. This large data area
permits fast throughput of data from the processor to the module.
The following illustration shows the data transfer method used to move data
between the ControlLogix processor, the MVI56-103M module, and the serial
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 defined in
the controller tags. The user is responsible for handling and interpreting all data
received on the application ports and transferred to the input image.