Backplane Data Transfer; Processor - ProSoft Technology MVI69-GSC CompactLogix User Manual

MVI69-GSC ♦ CompactLogix or MicroLogix Platform
Generic ASCII Serial Communication Module
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.
The following illustration shows the data transfer method used to move data between the
CompactLogix processor, the MVI69-GSC module and the network.
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