
System window watchdog (WWDG)
RM0453
986/1454
RM0453 Rev 2
Note:
The T6 bit can be used to generate a software reset (the WDGA bit is set and the T6 bit is
cleared).
31.3.5
How to program the watchdog timeout
Use the formula in
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 272. 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
tWWDG tPCLK 4096 2
WDGTB[2:0]
T 5:0
[
]
1
+
(
)
×
×
×
=
ms
(
)