Cypress FM4 Series - Page 147

CHAPTER 3: Clock Supervisor
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 147
Anomalous Frequency Detection
Figure 5-3 provides an example of anomalous frequency detection function operation.
Figure 5-3 Example of Anomalous Frequency Detection Function Operation
Main clock
Divided clock of
High-speed CR
Count-up cycle
1. This function detects rising edges of the divided clock of high-speed CR.
2. After detecting edges, it counts up clocks using the main clock.
3. It keeps counting up until it detects the next rising edge of the divided clock of high-speed CR.
4. Let "α" be the count value with the main clock.
Also let A denote the lower window value, and B the upper window value. Compare the count value α
with those window values and if expression
A ≤ α ≤ B
holds true, then the frequency is considered to be normal.
If the count value α is out of the range, i.e., either
α<A, or B<α
is true, then the frequency is considered to be anomalous, and an interrupt occurs.
If the interrupt flag has not been cleared after the interrupt and an anomalous frequency is detected
again, then the function issues a reset depending on the setting.