ProSoft Technology MVI69-DFNT - Manual (Page 83)

MVI69-DFNT ♦ CompactLogix or MicroLogix Platform Reference
EtherNet/IP Client/Server Communication Module User Manual
ProSoft Technology, Inc. Page 83 of 167
May 14, 2014
5.2.2 Normal Data Transfer
Normal data transfer includes the paging of the user data found in the module’s
internal database and the Status Data. These data are transferred through Read
(input image) and Write (output image) Bocks. Refer to the Module Configuration
section for a description of the data objects used with the blocks. The structure
and function of each block is discussed in the following topics.
Read Block
These blocks of data transfer information from the module to the CompactLogix
or MicroLogix. The structure of the input image used to transfer this data is
shown below:
Offset Description Length
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).
The Read Block ID is an index value used to determine where the data will be
placed in the CompactLogix or MicroLogix controller tag ReadData array.
The Write Block ID contained in the read block is used by ladder logic to decide
what portion of the WriteData array to send to the module from the
CompactLogix or MicroLogix.
Write Block
These blocks of data transfer information from the CompactLogix or MicroLogix
to the module. The following table describes the structure of the output image.
Offset Description Length
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 used to determine the location in the
module’s database where the data will be placed.
How Data is Transferred
In order to understand how the data is transferred between the processor and the
module, you must understand the concept of Read Data and Write Data areas in
the module’s internal memory database. The Read Data Area will be transferred
from the module to the CompactLogix or MicroLogix. The Write Data Area will be
transferred from the CompactLogix or MicroLogix to the module.