ProSoft Technology MVI69-DNPSNET - Manual (Page 66)

MVI69-DNPSNET ♦ CompactLogix or MicroLogix Platform Reference
Distributed Network Protocol Interface Module
Page 66 of 119 ProSoft Technology, Inc.
November 3, 2008
Main Logic Loop
Upon completing the power up configuration process, the module enters an
infinite loop that performs the functions shown in the following diagram.
Backplane Data Transfer
The MVI69-DNPSNET module communicates directly over the CompactLogix or
MicroLogix backplane. Data is paged between the module and the CompactLogix
or MicroLogix 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.
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 can be set to 62, 122 or 242 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 can be set to 61, 121 or 241
words. This large data area permits fast throughput of data from the processor to
the module.