ProSoft Technology MVI71-DFNT - Manual (Page 71)

MVI71-DFNT ♦ PLC 5 Reference
EtherNet/IP Client/Server Communication Module User Manual
ProSoft Technology, Inc. Page 71 of 175
February 3, 2011
5.2.2 Normal Data Transfer
Normal data transfer includes the transferring of data between the MVI71-DFNT
database and the PLC data files. These data are transferred through read (BTR)
and write (BTW) blocks. Refer to the Module Configuration section for a
description of the ladder logic required to perform the data movement within the
PLC processor. The structure and function of each block is discussed in the
following topics.
These blocks of data transfer information from the module to the PLC processor.
When data is received on one of the servers, a data block is built. The structure
of this block type is shown in the following table.
Read Block
Word Offset Description
0 Read Block ID
1 Next Write Block ID
2 to 63 Read Data
These blocks of data transfer information from the PLC processor to the module.
The structure of the BTW block is shown in the following table.
Write Block
Word Offset Description
0 Write Block ID (copied from the previous Read block)
1 to 63 Write Data
The following shows the valid block IDs for normal transfer:
Block ID Definition
-1 and 0 Null blocks that do not contain any data.
1 to 67 Data read and write blocks to transfer data for the module’s database
between the processor and the module.
In order to understand how the data is transferred between the processor and the
module, you must understand the Read Data and Write Data area concept in the
module’s database. The module’s database can be partially, or totally divided
into Read Data Areas and Write Data Areas.
How Data is Transferred
These areas are defined by the user when the configuration file is being edited.
The following parameters define the Read and Write data areas:
Read Register Start = 0
Read Register Count = 120
Write Register Start = 200
Write Register Count = 120
Each area is broken down into blocks of 60 words. Therefore, the Read Register
Count and Write Register Count parameters should be multiples of 60.