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Nations Technologies Inc.
Tel
:
+86-755-86309900
:
Address: Nations Tower, #109 Baoshen Road, Hi-tech Park North.
Nanshan District, Shenzhen, 518057, P.R.China
decrement speed of the counter. WWDG_CFG.W[6:0] bits set the upper limit of the window.
When the down-counter is refreshed before reaching the window register value or after WWDG_CTRL.T6 bit
becomes 0, a system reset will be generated. Figure 17-2 describes the working process of the window register.
Set the WWDG_CFG.EWINT bit to enable early wake-up interrupt. When the count-down counter reaches 0x40, an
interrupt will be generated. You can analyze the cause of software failure or save important data in the corresponding
interrupt service routine (ISR), and reload the counter to prevent WWDG from resetting. Write '0' to the
WWDG_STS.EWINTF bit to clear the interrupt.
Timing for refresh watchdog and interrupt generation
Figure 17-2 Refresh window and interrupt timing of WWDG
Watchdog refreshing window is between WWDG_CFG.W[6:0] value (maximum value 0x7F) and 0x3F, refresh
outside this window will generates reset request to MCU. Counter count down from 0x7F to 0x3F using scaled APB1
clock, the maximum counting time and minimum counting time is shown in Table 17-1 (assuming APB1 clock 36
MHz) with calculate equation:
Time
CNT DownCounter
T[6:0]
W[6:0]
0x3F
Refresh not allowed
Refresh allowed
0x41
0x40
0x3F
T
PCLK
× 4096 × 2
TIMERB
EWINTF = 0
WWDG_EWINT
Reset
T[6] value