Rockwell Automation Publication 1756-UM001M-EN-P - February 2012 169
Develop Applications Chapter 10
Some object types appear repeatedly, so you may have to specify the object name.
For example, there can be several tasks in your application. Each task has its own
Task object that you access by the task name.
There are several objects and attributes that you can use the GSV and SSV
instructions to monitor and set the system. For more information about GSV
instructions, SSV instructions, objects, and attributes see the Logix5000
Controllers General Instructions Reference Manual, publication 1756-RM003
.
Monitoring I/O Connections
If communication with a device in the I/O configuration of the controller does
not occur for 100 ms or 4 times the RPI, whichever is less, communication times
out and the controller produces these warnings:
• An I/O fault status code is indicated on the status display of the 1756-L7x
controller.
• The I/O status indicator on the front of the 1756-L6x controller flashes
green.
• A
shows over the I/O configuration folder and over the devices that
have timed out.
• A module fault code is produced, which you can access via the following:
– The Module Properties dialog box
– A GSV instruction
For more information about I/O faults, see the Major, Minor, and I/O Faults
Programming Manual, publication 1756-PM014
.
Determine if I/O Communication has Timed Out
In the programming example, the instructions are used to complete these tasks.
This example could be used with either the 1756-L7x or 1756-L6x controllers:
• The GSV instruction gets the status of the I/O status indicator (via the
LEDStatus attribute of the Module object) and stores it in the
IO_LED tag.
• IO_LED is a DINT tag that stores the status of the I/O status indicator or
status display on the front of the controller.
• If IO_LED equals 2, than at least one I/O connection has been lost and
the Fault_Alert is set.
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