
Window watchdog (WWDG)
RM0008
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Doc ID 13902 Rev 12
20.4
How to program the watchdog timeout
to calculate the WWDG timeout.
Warning:
When writing to the WWDG_CR register, always write 1 in the
T6 bit to avoid generating an immediate reset.
Figure 184. Window watchdog timing diagram
20.5 Debug
mode
When the microcontroller enters debug mode (Cortex-M3 core halted), the WWDG counter
either continues to work normally or stops, depending on DBG_WWDG_STOP configuration
bit in DBG module. For more details, refer to
Section 31.16.2: Debug support for timers,
.
T6 bit
Reset
W[6:0]
T[6:0] CNT downcounter
time
Refresh window
Refresh not allowed
0x3F
The formula to calculate the timeout value is given by:
where:
T
WWDG
: WWDG timeout
T
PCLK1
: APB1 clock period measured in ms
Min-max timeout value @36 MHz (PCLK1)
WDGTB
Min timeout value
Max timeout value
0
113 µs
7.28 ms
1
227 µs
14.56 ms
2
455 µs
29.12 ms
3
910 µs
58.25 ms
T
WWDG
T
PCLK1
4096
×
2
WDGTB
×
T 5:0
[
]
1
+
(
)
×
=
ms
(
)