Ladder Logic
MVI56-DH485R
♦
ControlLogix Platform
User Manual
DH485 Interface Module for Remote Chassis
ProSoft Technology, Inc.
Page 35 of 97
August 27, 2009
3 Ladder
Logic
In This Chapter
Module Data Object (DH485ModuleDef) ...............................................35
Adding the Module to an Existing Project .............................................. 38
Ladder logic is required for application of the MVI56-DH485R module. Tasks that
must be handled by the ladder logic are module data transfer, special block
handling, and status data receipt. Additionally, a power-up handler may be
needed to handle the initialization of the module’s data and to clear any
processor fault conditions.
The sample ladder logic, on the ProSoft Solutions CD-ROM, is extensively
commented, to provide information on the purpose and function of each rung. For
most applications, the sample ladder will work without modification.
3.1
Module Data Object (DH485ModuleDef)
All status and variable data related to the MVI56-DH485R module is stored in a
user defined data type. An instance of the data type is required before the
module can be used. This is done by declaring a variable of the data type in the
Controller Tags Edit Tags dialog box. The following table describes the structure
of this object.
Name Data
Type
Description
InStat
DH485InStat
Status information in each read block
ReadData
INT[600]
Data read from module
WriteData
INT[600]
Data to write to module
BP
DH485Backplane
Data to handle backplane logic
Port1CmdsProcessed INT
Port2CmdsProcessed INT
DH485_1Port1CmdControl BOOL[32]
DH485_1Port2CmdControl BOOL[32]
This object contains objects that define variables to be used with the module and
status data related to the module. Each of these object types is discussed in the
following topics of the document.
