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Independent watchdog (IWDG)

RM0016

 

 

14.3IWDG registers

14.3.1Key register (IWDG_KR)

Address offset: 0x00

Reset value: 0xXX

7

6

5

4

3

2

1

0

KEY[7:0]

w

Bits 7:0 KEY[7:0]: Key value

The KEY_REFRESH value must be written by software at regular intervals, otherwise the watchdog generates an MCU reset when the counter reaches 0.

If the IWDG is not enabled by option byte (see datasheet for option byte description), the KEY_ENABLE value is the first value to be written in this register.

KEY_ENABLE value = 0xCC

Writing the KEY_ENABLE value starts the IWDG.

KEY_REFRESH value = 0xAA

Writing the KEY_REFRESH value refreshes the IWDG.

KEY_ACCESS value = 0x55

Writing the KEY_ACCESS value enables the access to the protected IWDG_PR and IWDG_RLR registers (see Section 14.2).

14.3.2Prescaler register (IWDG_PR)

Address offset: 0x01

Reset value: 0x00

7

6

5

4

3

2

1

0

 

 

 

 

 

 

 

 

 

 

Reserved

 

 

 

PR[2:0]

 

 

 

 

 

 

 

 

 

 

 

 

 

rw

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bits 7:3

Reserved

 

 

 

 

 

 

Bits 2:0

PR[2:0]: Prescaler divider

 

 

 

 

 

 

These bits are write access protected (see Section 14.2). They can be written by software to select the

 

prescaler divider feeding the counter clock.

 

 

 

 

000: divider /4 001: divider /8 010: divider /16 011: divider /32

100:divider /64

101:divider /128

110:divider /256

111:Reserved

124/454

Doc ID 14587 Rev 9

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