How to calculate the window watchdog timer (WWDT) time-out interval?

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a_ziliu
Posts: 116
Joined: 20 Mar 2017, 10:52

27 Mar 2017, 14:30

The WWDT time-out interval is calculated as follows:
Pre-scale Value * Counter Value / FWWDT
Pre-scale Value: The pre-scale value
Counter Value: The maximum value of the counter, which is a constant 64
FWWDT: Clock source frequency of WWDT
There are two kinds of WWDT clock sources for selection:
HCLK / 2048
10 kHz (LIRC)
The WWDT has a 6-bit counter and a 11-bit pre-scaler. The pre-scale value can be set by the 4-bit PERIODSEL, as shown in the table below:

An example of the WWDT time-out interval calculation is as follows:
Example 1
When the WWDT clock source is 10 kHz and the pre-scaler is set to 2048,
Time-out interval = 2048 * 64 / 10k = 13.1072 s
Example 2
When the WWDT clock source is HCLK / 2048, HCLK is 48 MHz, and the pre-scaler is set to 8, then
Time-out interval = 8 * 64 / (48M / 2048) = 131.072 ms

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