RM0453 Rev 5 985/1450
RM0453 System window watchdog (WWDG)
988
31.3.5 How to program the watchdog timeout
Use the formula in Figure 273 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 273. Window watchdog timing diagram
The formula to calculate the timeout value is given by:
where:
t
WWDG
: WWDG timeout
t
PCLK
: APB clock period measured in ms
4096: value corresponding to internal divider
MS47266V1
W[6:0]
0x3F
0x41
0x40
0x3F
wwdg_ewit
wwdg_rst
Refresh not allowed Refresh allowed
Time
T[6:0]
T
pclk
x 4096 x 2
WDGTB
CNT DownCounter
T6 bit
EWIF = 0
t
WWDG
t
PCLK
4096 2
WDGTB[2:0]
T5:0[]1+()×××=ms()
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