A number of built-in alarms are available to monitor internal events. Several types of alarms and upsets are detected by this feature:
- C-PLL is not locked
- S-PLL is not locked
- JESD204C link is not transmitting data (not in the data transmission state)
- SYSREF causes internal clocks to be realigned
- An upset that impacts the internal clocks
- A read or write error generated by the digital to serializer synchronizing FIFO
When an alarm occurs, a bit for each specific alarm is set in
ALM_STATUS. Each alarm bit remains set until the host system writes a 1 to clear the alarm. If the alarm type is not masked (see the
ALM_MASK register), then the alarm is also indicated by the
ALARM register. The CALSTAT output pin can be configured as an alarm output that goes high when an alarm occurs; see
CAL_STATUS_SEL.