Independent watchdog (IWDG)
RM0090
DocID018909 Rev 11
with a different value will break the sequence and register access will be protected again.
This implies that it is the case of the reload operation (writing 0xAAAA).
A status register is available to indicate that an update of the prescaler or the down-counter
reload value is on going.
21.3.3 Debug
mode
When the microcontroller enters debug mode (Cortex
®
-M4 with FPU core halted), the IWDG
counter either continues to work normally or stops, depending on DBG_IWDG_STOP
configuration bit in DBG module. For more details, refer to
Section 38.16.2: Debug support
for timers, watchdog, bxCAN and I2C
.
Figure 213. Independent watchdog block diagram
Note:
The watchdog function is implemented in the V
DD
voltage domain that is still functional in
Stop and Standby modes.
)7$'RESET
PRESCALER
)7$'?02
0RESCALERREGISTER
)7$'?2,2
2ELOADREGISTER
BIT
,3)
K(Z
)7$'?+2
+EYREGISTER
#/2%
6$$VOLTAGEDOMAIN
)7$'?32
3TATUSREGISTER
-36
BITRELOADVALUE
BITDOWNCOUNTER
Table 106. Min/max IWDG timeout period at 32 kHz (LSI)
(1)
1. These timings are given for a 32 kHz clock but the microcontroller internal RC frequency can vary. Please
refer to the LSI oscillator characteristics table in the device datasheet for maximum and minimum values.
Prescaler divider
PR[2:0] bits
Min timeout (ms) RL[11:0]=
0x000
Max timeout (ms) RL[11:0]=
0xFFF
/4
0
0.125
512
/8
1
0.25
1024
/16
2
0.5
2048
/32
3
1
4096
/64
4
2
8192
/128
5
4
16384
/256
6
8
32768