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NuMicro® NUC029LEE/NUC029SEE
32-bit Arm
®
Cortex
®
-M0 Microcontroller
Aug, 2018
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Figure 6.11-2 Window Watchdog Timer Block Diagram
6.11.4 Basic Configuration
The WWDT peripheral clock is enabled in APBCLK[0] and clock source can be selected in
CLKSEL2[17:16].
6.11.5 Functional Description
The Window Watchdog Timer (WWDT) includes a 6-bit down counter with programmable
prescale value to define different WWDT time-out intervals.
The clock source of 6-bit WWDT is based on system clock divide 2048 (HCLK/2048) or internal
10 kHz oscillator with a programmable 11-bit prescale counter value which controlled by
PERIODSEL (WWDTCRL[11:8]) setting. Also, the correlate of PERIODSEL and prescale value
are listed in the Table 6.11-1.
PERIODSEL
Prescaler Value
Max. Time-Out Period
Max. Time-Out Interval
(WWDT_CLK=10 KHz)
0000
1
1 * 64 * T
WWDT
6.4 ms
0001
2
2 * 64 * T
WWDT
12.8 ms
0010
4
4 * 64 * T
WWDT
25.6 ms
0011
8
8 * 64 * T
WWDT
51.2 ms
0100
16
16 * 64 * T
WWDT
102.4 ms
0101
32
32 * 64 * T
WWDT
204.8 ms
0110
64
64 * 64 * T
WWDT
409.6 ms
0111
128
128 * 64 * T
WWDT
819.2 ms
1000
192
192 * 64 * T
WWDT
1.2288 s
1001
256
256 * 64 * T
WWDT
1.6384 s
1010
384
384 * 64 * T
WWDT
2.4576 s
1011
512
512 * 64 * T
WWDT
3.2768 s
1100
768
768 * 64 * T
WWDT
4.9152 s
1101
1024
1024 * 64 * T
WWDT
6.5536 s
1110
1536
1536 * 64 * T
WWDT
9.8304 s
1111
2048
2048 * 64 * T
WWDT
13.1072 s
Table 6.11-1 Window Watchdog Timer Prescale Value Selection
WWDT Counting
When the WWDTEN bit is set, WWDT down counter will start counting from 0x3F to 0. To prevent
program runs to disable WWDT counter counting unexpected, the WWDT control register
WWDTCR can only be written once after chip is powered on or reset. User cannot disable WWDT
counter counting (WWDTEN), change counter prescale period (PERIODSEL) or change window
compare value (WINCMP) while WWDTEN (WWDTCR[0]) bit has been enabled by software