ProSoft Technology MVI69E-MBTCP - Manual (Page 65)

MVI69E-MBTCP ♦ CompactLogix Platform MVI69E-MBTCP Backplane Data Exchange
Modbus TCP/IP Enhanced Communication Module User Manual
ProSoft Technology, Inc. Page 65 of 150
May 20, 2015
4.3 Normal Data Transfer
Normal data transfer includes the paging of the user data found in the module’s
internal database (Registers 0 to 9999) and the status data. These data are
transferred through read (input image) and write (output image) blocks. The
following topics describe the structure and function of each block.
4.3.1 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 Description Length (words)
0 Write Block ID 1
1 to (n) Write Data (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.
4.3.2 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 Description Length (words)
0 Read Block ID 1
1 Write Block ID 1
2 to (n+1) Read Data (n)
(n) = 60, 120, or 240 depending on the Block Transfer Size parameter (refer to the configuration
file).