Ladder logic is required for application of the MVI69-DNP 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 Objects

All data related to the MVI69-DNP is stored in two user defined data types. One
contains the status data and the other contains the DNP and IED datasets. Two
structures were used for ease of use. Any time an array's size is altered in the
RSLogix 5000 software, all the data in the object is set to zero. Because the
array sizes may need to be adjusted for the data types in an application, this data
is placed in a separate object.

An instance of each data type is required before the module can be used. This is
accomplished by declaring variables of the data types in the Controller Tags Edit
Tags dialog box. Each object is discussed in the following topics:

3.1.1 DNPModuleDef

Object

The DNPModuleDef object contains all the MVI69-DNP module status data. The
structure of the object is displayed in the following example:

Tag Name

Data Type

Description

GenStat

DNPSlvStat

General status information

ErrList

INT[60]

List of last 60 slave errors

DNPBackplane

Data to handle backplane logic

CmdLstErr DNPCmdLstErr

ComErrTble DNPComErrTble

Readclock DNPtime_n_date

WriteClock DNPtime_n_date