Pre-scale Value * Counter Value / F_WWDTPre-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:

PERIODSEL	Pre-scale Value	PERIODSEL	Pre-scale Value
0000	1	1000	192
0001	2	1001	256
0010	4	1010	384
0011	8	1011	512
0100	16	1100	768
0101	32	1101	1024
0110	64	1110	1536
0111	128	1111	2048

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

Products:	Microcontrollers ,8bit 8051 MCUs ,Arm Cortex-M0 MCUs ,Arm Cortex-M4 MCUs
Applications:
Function:	Peripherals,Timer and PWM,Window Watchdog Timer (WWDT)

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How to calculate the window watchdog timer (WWDT) time-out interval? Issue Date：2016-11-29

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