Reference MVI56-DH485R
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ControlLogix Platform
User Manual
DH485 Interface Module for Remote Chassis
ProSoft Technology, Inc.
Page 73 of 97
August 27, 2009
Write Access
In order to control data contained in the DH485R driver module, a write
command message must be executed from the ladder logic. 242 bytes are
available in the CIF Read Data area (address 0 to 241). To alter the CIF data
area in the module, select the 485CIF option for the Target Device in the MSG
instruction. The following is an example rung that displays a CIF method MSG
instruction:
You must allocate a unique area in the ControlLogix’s data file area for the
Control Block area used by the MSG instruction. Failure to provide this area will
result in unpredictable behavior. Select the Setup Screen area in the MSG
instruction to display the following dialog box:
This example will place the 10 words from the ControlLogix data file N9:0 to 9 in
the CIF data area starting at byte offset 100 in node 2. Note that the Data Table
Offset value is a byte offset and not a word offset. The size of data written is
determined by the number of elements times the size of each element. For a N-
type file, the size is 1 word (2 bytes). For a F-type file, the size is 2 words (4
bytes).
Data File Access
The data file access method permits full access to the full internal database of
the DH-485 driver module. This access method supports normal SLC file read
and write access to the data in the module.
