Backplane Data Transfer - ProSoft Technology MVI56-PNPM User Manual

MVI56-PNPM ♦ ControlLogix Platform
Phantom Network Protocol Master Communication Module

5.2.3 Backplane Data Transfer

The MVI56-PNPM module communicates directly over the ControlLogix
backplane. Data is paged between the module and the ControlLogix 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 2 to 10 milliseconds.
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 set to 250 words. 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 is set to 248 words. 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-PNPM module and the Phantom
Network.
ControlLogix Processor
ControlLogix Processor
Controller Tags
Status
Read Data
Write Data
Special Control
Blocks
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Ladder
Logic
Transfers
Data from r
Input Image
module's input
image to data
areas in the
processor
Ladder
Logic
Transfers
Data from Output image
Processor
data areas
Command or
to output image
MVI56 -PNPM Module
Module's
Internal
Database
Master Master
Driver Driver
Logic Logic
Event
Control
Reference
Modbus
Port
Drivers
To
Network
ProSoft Technology, Inc.
January 2, 2008