ProSoft Technology ControlLogix MVI56E-SMGC User Manual page 71

MVI56E-SMGC ♦ ControlLogix™ Platform
Enhanced FMC722 TPU General Communication Module
5.2.1.3 Backplane Data Transfer
The MVI56E-SMGC 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 module 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 164 bytes. This data area permits fast throughput between the module
and the processor and permits space for the maximum response message.
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 Ethernet network.
Each message is directed to the client that is connected to the remote server. The output
image for the module is set to 56 bytes. This data area permits fast throughput of data
from the processor to the module and is large enough to hold the largest request
message.
The following illustration shows the data transfer method used to move data between the
ControlLogix processor, the MVI56E-SMGC module, and the Ethernet network.
As shown in the previous diagram, 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. Additionally,
the user is responsible for constructing messages to be transferred out of the module by
building the messages in the output image of the module.
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Reference
User Manual
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