ProSoft Technology MVI69-GSC - Manual (Page 74)

Reference MVI69-GSC ♦ CompactLogix or MicroLogix Platform
User Manual Generic ASCII Serial Communication Module
Page 74 of 102 ProSoft Technology, Inc.
September 24, 2010
5.2.2 Data Flow between MVI69-GSC Module and CompactLogix
Processor
The following topics describe the flow of data between the two pieces of
hardware (CompactLogix processor and MVI69-GSC module) and other devices
on the network under the module’s different operating modes.
Backplane Data Transfer
The MVI69-GSC module communicates directly over the CompactLogix or
MicroLogix 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.
The data is paged between the processor and the module using input and output
image blocks (fixed at 60 words).
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 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.