How To Program The Watchdog Timeout; Figure 156. Window Watchdog Timing Diagram - ST STM32F102 Series Reference Manual

Window watchdog (WWDG)
17.4

How to program the watchdog timeout

Figure 156
Watchdog Counter (CNT) and the resulting timeout duration in milliseconds. This can be
used for a quick calculation without taking the timing variations into account. If more
precision is needed, use the formulae in
Warning:

Figure 156. Window watchdog timing diagram

The formula to calculate the timeout value is given by:
where:
T
WWDG
T
PCLK1
Min-max timeout value @36MHz (PCLK1)
362/690
shows the linear relationship between the 6-bit value to be loaded in the
When writing to the WWDG_CR register, always write 1 in the
T6 bit to avoid generating an immediate reset.
T[6:0] CNT downcounter
W[6:0]
3Fh
Refresh not allowed
T6 bit
Reset
T WWDG = T PCLK1
: WWDG timeout
: APB1 Clock period measured in ms
WDGTB
0
1
2
3
Figure 156.
Refresh Window
WDGTB
× ×
4096 2
Min timeout value
113 µs
227 µs
455 µs
910 µs
time
× ( [ ] ) (
T 5:0 + 1 ; ms
Max timeout value
7.28 ms
14.56 ms
29.12 ms
58.25 ms
RM0008
)