Normal Data Transfer; Write Block: Request From The Processor To The Module; Read Block: Response From The Module To The Processor - ProSoft Technology CompactLogix MVI69E-MBS User Manual

MVI69E-MBS ♦ CompactLogix™ Platform
Modbus Serial Enhanced Communication Module
All data transferred between the module and the processor over the backplane is
through the input and output images. Ladder logic in the CompactLogix or MicroLogix
1500-LRP processor interfaces the input and output image data with data defined in the
Controller Tags. All data used by the module is stored in its internal database. This
database is defined as virtual MBS data tables with addresses from 0 to the maximum
number of points for each data type.
5.3

Normal Data Transfer

5.3.1 Write Block: Request from the Processor to the Module

These blocks of data transfer information from the processor to the module. The
structure of the output image used to transfer this data is shown below:
Offset
0
1 to (n)
(n) = 60, 120, or 240 depending on the Block Transfer Size parameter (refer to the configuration file).
The Write Block ID is an index value that determines the location in the module's
database where the data is placed.

5.3.2 Read Block: Response from the Module to the Processor

These blocks of data transfer information from the module to the processor. The
structure of the input image used to transfer this data is shown below:
Offset
0
1
2 to (n+1)
(n) = 60, 120, or 240 depending on the Block Transfer Size parameter (refer to the configuration file).
ProSoft Technology, Inc.
Description
Write Block ID
Write Data
Description
Read Block ID
Write Block ID
Read Data
MVI69E-MBS Backplane Data Exchange
Length (words)
1
(n)
Length (words)
1
1
(n)
User Manual
Page 68 of 159