ProSoft Technology MVI69-ADM - Manual (Page 37)

MVI-ADM ♦ 'C' Programmable Understanding the MVI-ADM API
'C' Programmable Application Development Module Developer's Guide
ProSoft Technology, Inc. Page 37 of 342
February 20, 2013
MVI69 Backplane Data Transfer
The MVI69-ADM module communicates directly over the 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 2 to 10 milliseconds.
You can configure the size of the blocks using the Block Transfer Size parameter
in the configuration file. You can configure blocks of 60, 120, or 240 words of
data depending on the number of words allowed for your own application.
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 may be set to 62, 122, or 242 words depending on
the block transfer size parameter set in the configuration file.
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 may be set to 61, 121, or 241
words depending on the block transfer size parameter set in the configuration
file.
The following illustration shows the data transfer method used to move data
between the CompactLogix processor and the MVI69-ADM module.