1、概述

看门狗有两个作用：1、可以防止程序跑飞，若程序跑飞可让单片机复位；2、可作为间隔时间发生器，在中断中进行定期刷新显示、读取数据等对外设的操作。

2、设置

不需要看门狗时可用软件关闭，设置：WDTCTL = WDTPW + WDTHOLD;

为防止误触发操作WDTCTL需要先写入WDTPW。

作为间隔定时器时详细操作可见MSP430F149.H文件中的宏定义。

3、相关寄存器

1、WDTCTL Watchdog Timer Register

WDTPW Bits

15-8

Watchdog timer password. Always read as 069h. Must be written as 05Ah, or

a PUC will be generated.

WDTHOLD Bit 7 Watchdog timer hold. This bit stops the watchdog timer. Setting WDTHOLD= 1 when the WDT is not in use conserves power.

0 Watchdog timer is not stopped

1 Watchdog timer is stopped

WDTTMSEL Bit 4 Watchdog timer mode select

0 Watchdog mode

1 Interval timer mode

WDTCNTCL Bit 3 Watchdog timer counter clear. Setting WDTCNTCL = 1 clears the ｃount value

to 0000h. WDTCNTCL is automatically reset.

0 No action

1 WDTCNT = 0000h

2、IE1 Interrupt Enable Register 1

WDTIE Bit 0 Watchdog timer interrupt enable. This bit enables the WDTIFG interrupt for

interval timer mode. It is not necessary to set this bit for watchdog mode.

Because other bits in IE1 may be used for other modules, it is recommended

to set or clear this bit using BIS.B or BIC.B instructions, rather than MOV.B

or CLR.B instructions.

0 Interrupt not enabLED

1 Interrupt enabled

4、设计实例

4.1 利用WDT定时模式在中断函数中定时操作外设

说明：#define WDT_MDLY_32 （WDTPW+WDTTMSEL+WDTCNTCL）

void main（void）

{

WDTCTL = WDT_MDLY_32; // Set Watchdog Timer interval to ~30ms

IE1 |= WDTIE; // Enable WDT interrupt

P2DIR |= 0x01; // Set P1.0 to output direction

_BIS_SR（LPM0_bits + GIE）; // Enter LPM0 w/ interrupt

}

// Watchdog Timer interrupt service routine

#pragma vector=WDT_VECTOR

__interrupt void watchdog_timer（void）

{

P2OUT ^= 0x01; // Toggle P1.0 using exclusive-OR

}

4.2 利用WDT定时模式延时

WDTCTL = WDT_ADLY_1000;//延时1000ms

//延时2s

for（i = 0; i < 3; i++）

IG1&= ~WDTIFG;

while（!（IFG1 & WDTIFG））

IFG1 &= ~WDTIFG;