ST STM32F207 series User Manual

Independent watchdog (IWDG) RM0033
498/1381 RM0033 Rev 9
17.4 IWDG registers
Refer to Section 2.2 on page 45 for a list of abbreviations used in register descriptions.
The peripheral registers have to be accessed by half-words (16 bits) or words (32 bits).
17.4.1 Key register (IWDG_KR)
Address offset: 0x00
Reset value: 0x0000 0000 (reset by Standby mode)
17.4.2 Prescaler register (IWDG_PR)
Address offset: 0x04
Reset value: 0x0000 0000
313029282726252423222120191817161514131211109876543210
Reserved
KEY[15:0]
wwwwwww w wwwwwwww
Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 KEY[15:0]: Key value (write only, read 0000h)
These bits must be written by software at regular intervals with the key value AAAAh,
otherwise the watchdog generates a reset when the counter reaches 0.
Writing the key value 5555h to enable access to the IWDG_PR and IWDG_RLR registers
(see Section 17.3.2)
Writing the key value CCCCh starts the watchdog (except if the hardware watchdog option is
selected)
313029282726252423222120191817161514131211109876543210
Reserved
PR[2:0]
rw rw rw
Bits 31:3 Reserved, must be kept at reset value.
Bits 2:0 PR[2:0]: Prescaler divider
These bits are write access protected seeSection 17.3.2. They are written by software to
select the prescaler divider feeding the counter clock. PVU bit of IWDG_SR must be reset in
order to be able to change the prescaler divider.
000: divider /4
001: divider /8
010: divider /16
011: divider /32
100: divider /64
101: divider /128
110: divider /256
111: divider /256
Note: Reading this register returns the prescaler value from the VDD voltage domain. This
value may not be up to date/valid if a write operation to this register is ongoing. For this
reason the value read from this register is valid only when the PVU bit in the IWDG_SR
register is reset.

ST STM32F207 series Specifications

General

Brand	ST
Model	STM32F207 series
Category	Microcontrollers
Language	English