ProSoft Technology MVI56E-LDM - Manual (Page 60)

Understanding the MVI56-LDM API ControlLogix Platform ♦ "C" Programmable
Developer's Manual Linux Application Development Module
Page 54 of 264 ProSoft Technology, Inc.
March 12, 2014
Creates a handle allowing access to the tag database of the controller by
invoking
OCXcip_CreateTagDbHandl
. Options for accessing the database are set
using
OCXcip_SetTagDbOptions
.
A test is then made to ensure that the local copy of the database matches the
controller's copy of the tag database. This is done using the
OCXcip_TestTagDbVer
routine which will return a database empty error on the first
invocation, causing the local database to be rebuilt with the
OCXcip_BuildTagDb
routine.
The database contents are then printed to the console via
print_database_symbols
.
print_data_symbols
calls
OCXcip_GetSymbolInfo
for
each symbol (i.e., Tag) in the controller. It prints the name, dimensions if its an
array, the element size, and the type of each tag. If the type is simple,
print_cip_data_type
is called. If the type is a structure,
print_structure_info
is
called to print information about each element of the structure.
print_structure_info
uses
OCXcip_GetStructInfo
to get information about a
structure and then prints the name, data type, number of members, and overall
size to the console. It then request info about each member using
OCXcip_GetStructMbrInfo and prints that information (name, array dimension,
offset in structure, element size, and data type) to the console. Again, a data
type may be simple (
print_cip_data_type
) or a structure which causes a
recursive invocation of the print_structure_info routine.
In the main program,
print_tag_info
is called on "index". This routine uses
OCXcip_GatTagDbTagInfo
to get information about this tag and prints that info to
the console.
The main loop then calls
print_controller_status
to check for changes in
controller status. This routine uses
OCXcip_GetDeviceIdStatus
to check the fault
state, run mode, and key switch mode of the controller. If any of these states
change, the new state is printed to the console.
The main loop then uses
OCXcip_AccessTagData
to read the value of the tag
"
LDM_Test
". The value of this tag is then incremented and written back to the
controller using the OCXcip_AccessTagData routine.