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Reference
MVI56E-MNETR ♦ ControlLogix Platform
User Manual
Modbus TCP/IP Interface Module with Reduced Data Block
Page 116 of 175
ProSoft Technology, Inc.
June 14, 2011
Block Response from Module to Processor
These blocks of data transfer information from the module to the ControlLogix
processor. The following table describes the structure of the input image.
Offset
Description
Length
0
Write Block ID
1
1 to 40
Read Data
40
41
Read Block ID
1
The Read Block ID is an index value used to determine the location of where the
data will be placed in the ControlLogix processor controller tag array of module
read data. Each transfer can move up to 40 words (block offsets 1 to 40) of data.
In addition to moving user data, the block also contains status data for the
module.
The Write Block ID associated with the block requests data from the ControlLogix
processor. Under normal program operation, the module sequentially sends read
blocks and requests write blocks.
For example, if the application uses three read and two write blocks, the
sequence will be as follows:
R1W1
→
R2W2
→
R3W1
→
R1W2
→
R2W1
→
R3W2
→
R1W1
→
This sequence will continue until interrupted by other write block numbers sent by
the controller or by a command request from a node on the Modbus network or
operator control through the module’s Configuration/Debug port.
Initialize Output Data
When the module performs a restart operation, it will request blocks of output
data from the processor to initialize the module’s output data (Read Data Area).
Use the
Initialize Output Data
parameter in the configuration file to bring the
module to a known state after a restart operation. The following table describes
the structure of the request block.
Offset
Description
Length
0
1000 to 1124
1
1 to 40
Spare
40
41
1000 to 1124
1