ProSoft Technology MVI56-MCM User Manual

Reference MVI56-MCM ♦ ControlLogix Platform
Modbus Communication Module
ProSoft Technology, Inc. Page 91 of 159
July 24, 2008
Offset Description Length
218 to 224 Port 2 Error Status 7
225 to 230 Data Transfer Status 6
231 Port 1 Current Error/Index 1
232 Port 1 Last Error/Index 1
233 Port 2 Current Error/Index 1
234 Port 2 Last Error/Index 1
235 to 248 Spare 14
249 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 200 words (block offsets 2 to 201) of
data. In addition to moving user data, the block also contains status data for the
module. This last set of data is transferred with each new block of data and is
used for high-speed data movement.
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 three read and two write
blocks are used with the application, 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.
Write Block
These blocks of data transfer information from the ControlLogix processor to the
module. The structure of the output image used to transfer this data is shown in
the following table:
Offset Description Length
0 Write Block ID 1
1 to 200 Write Data 200
201 to 247 Spare 47
The Write Block ID is an index value used to determine the location in the
module's database where the data will be placed. Each transfer can move up to
200 words (block offsets 1 to 200) of data.
8.2.7 Configuration Data Transfer
When the module performs a restart operation, it will request configuration
information from the ControlLogix processor. This data is transferred to the
module in specially formatted write blocks (output image). The module will poll for
each block by setting the required write block number in a read block (input
image). Refer to Integrating the Sample Ladder Logic into an Existing Project
(page 142) for a description of the data objects used with the blocks and the
ladder logic required. The format of the blocks for configuration is given in the
following topics.

ProSoft Technology MVI56-MCM Specifications

General

Brand	ProSoft Technology
Model	MVI56-MCM
Category	Cell Phone
Language	English