iwdg.h

Independent Watchdog (IWDG) support.

Usage Note

To use the independent watchdog, first call iwdg_init() with the appropriate prescaler and IWDG counter reload values for your application. Afterwards, you must periodically call iwdg_feed() before the IWDG counter reaches 0 to reset the counter to its reload value. If you do not, the chip will reset.

Once started, the independent watchdog cannot be turned off.

Types

struct iwdg_reg_map

Independent watchdog register map type.

Public Members

__io uint32 KR

Key register.

__io uint32 PR

Prescaler register.

__io uint32 RLR

Reload register.

__io uint32 SR

Status register.

iwdg_prescaler enum

Independent watchdog prescalers.

These divide the 40 kHz IWDG clock.

Values:

• IWDG_PRE_4 = IWDG_PR_DIV_4 -

  Divide by 4.

• IWDG_PRE_8 = IWDG_PR_DIV_8 -

  Divide by 8.

• IWDG_PRE_16 = IWDG_PR_DIV_16 -

  Divide by 16.

• IWDG_PRE_32 = IWDG_PR_DIV_32 -

  Divide by 32.

• IWDG_PRE_64 = IWDG_PR_DIV_64 -

  Divide by 64.

• IWDG_PRE_128 = IWDG_PR_DIV_128 -

  Divide by 128.

• IWDG_PRE_256 = IWDG_PR_DIV_256 -

  Divide by 256.

Devices

None at this time.

Functions

void iwdg_init(iwdg_prescaler prescaler, uint16 reload)

Initialise and start the watchdog.

The prescaler and reload set the timeout. For example, a prescaler of IWDG_PRE_32 divides the 40 kHz clock by 32 and gives roughly 1 ms per reload.

Parameters:

• prescaler -

  Prescaler for the 40 kHz IWDG clock.

• reload -

  Independent watchdog counter reload value.

void iwdg_feed(void)

Reset the IWDG counter.

Calling this function will cause the IWDG counter to be reset to its reload value.

Register Map Base Pointers

IWDG_BASE

Independent watchdog base pointer.

Register Bit Definitions

Key register

IWDG_KR_UNLOCK

IWDG_KR_FEED

IWDG_KR_START

Prescaler register

IWDG_PR_DIV_4

IWDG_PR_DIV_8

IWDG_PR_DIV_16

IWDG_PR_DIV_32

IWDG_PR_DIV_64

IWDG_PR_DIV_128

IWDG_PR_DIV_256

Status register

IWDG_SR_RVU_BIT

IWDG_SR_PVU_BIT

IWDG_SR_RVU

IWDG_SR_PVU