Functional Overview; General Concepts; Backplane Data Flow - ProSoft Technology MVI69E-GSC User Manual

MVI69E-GSC ♦ CompactLogix™ or MicroLogix™ Platform
8.2

Functional Overview

8.2.1 General Concepts

The MVI69E-GSC module uses ladder logic to communicate with the CompactLogix or
MicroLogix 1500-LRP processor across the backplane. The ladder logic handles the module
data transfer, configuration data transfer, special block handling, and status data receipt.
The following topics describe several concepts that are important for understanding the
operation of the MVI69E-GSC module. This is the order of operations on power-up:
1 The module begins the following logical functions:
Initialize hardware components
o
Initialize CompactLogix or MicroLogix 1500-LRP backplane driver
o
o Test and clear all RAM
2 Read configuration from the CompactLogix or MicroLogix 1500-LRP processor
through ladder logic
3 Allocate and initialize Module Register space
4 Enable application port(s)
After the module has received the module configuration, the module begins communicating
with other devices on the network, depending on the configuration of the module.

8.2.2 Backplane Data Flow

The following topics describe the flow of data between the hardware (CompactLogix
processor and MVI69E-GSC module) and other devices on the network under the module's
different operating modes.
Backplane Data Transfer
The MVI69E-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.
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