Safety Considerations Guide for Triconex General ... - ICEWeb

Development Guidelines 45
Array Index Errors
If an array index error is detected during runtime, the default behavior is to trap. This results in
the Tri-GP controller going to the safe state, with all outputs de-energized.
If your application requires some other behavior, you can use a CHK_ERR function block to
detect the error, and a CLR_ERR function block to clear the error and prevent a trap.
Note
If an array index is too small or too large, the array operation is performed on the last
element of the array. Array bounds checking is always turned on—there is no means to
disable the array index checking.
See the TriStation 1131 Libraries Reference for more information about the CHK_ERR and
CLR_ERR function blocks.
Infinite Loops
If the actual scan time exceeds the maximum allowable scan time for the Tri-GP controller, the
main processors will reset, causing the Tri-GP controller to go to the safe state, with all outputs
de-energized. The maximum allowable scan time for the Tri-GP is 450 milliseconds.
Although it is not possible to program an endless loop with TriStation 1131 software, it is
possible to create a loop with a very long time, enough to increase the actual scan time beyond
the controller’s maximum allowable scan time.
See Setting Scan Time on page 47 for more information about actual and maximum scan times.
Safety Considerations Guide for Triconex General Purpose v2 Systems