<9. Advanced Engineering >
200
TI 34P02K35-02E May 31, 2017-00
From all these values, we know that device label AI001 is in error (BAD) condition
due to severed wire or hardware failure, and as a result, an IOP+ (High Input Open)
alarm is generated in NPAS_PVI_1, and the status of the PV value becomes BAD.
● Reading Mode, Status and Alarm from an Application
Values corresponding to each mode, status and alarm condition of NPAS_POU are
predefined as system global variables.
These global variables can be used in control applications to check for specific
mode, status or alarm conditions.
The figure below shows a subset of system global variables related to alarms.
A complete list of system global variables accessible in NPAS POUs is given in
Appendix A, “List of Global Variables” of IM34P02P25-01E, “NPAS_POU –
Overview.”
For instance, the high-high limit alarm (HH) value of DWORD#00080000 is set as
the initial value of global variable GM_ALRM_HH. By comparing the alarm of an
NPAS POU against GM_ALRM_HH, a control application can check for the HH
alarm condition.
However, multiple mode, status and alarm condition bits may sometimes be set as
described earlier in the "Example with high-high limit (HH) and high limit alarms (HI)
detected.” In the example, the alarm value is DWORD#00088000, which is not
identical to DWORD#00080000 (GM_ALRM_HH) so a direct comparison using an
EQ function will fail to detect the HH alarm condition.
Instead, the logic shown below should be used for the comparison.
Summary of Contents for STARDOM FCN-500
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