Tiny4412中断之看门狗

　　一：看门狗（WDT watch dog timer）

　　看门狗其实是一个计数器，它的作用就是防止程序陷入死循环或者程序运行跑飞；看门狗是一个硬件，它的工作原理是，初始化给他一个值，它会过一段时间减一，直到这个数减为0，它将会产生一个中断信号或者reset信号，致使我们系统复位，而又时候我们不想让它过一会儿就重启又想预防死机，那么我们就可以在这个数减到快要接进0的时候，给它重新赋值；这样就不会触发reset信号，但当程序跑飞时机器死机时，它就会减到零，进行操作系统复位；

　 具体看下图所示：输入时钟为PCLK（该时钟频率等于系统的主频），它经过两级分频(Prescaler和frequency division factor)，最后将分频后的时钟作为该定时器的输入时钟，当计数器期满后可以产生中断或者复位信号。

　　看门狗计数器公式如下：

　　t_watchdog = 1/( PCLK / (Prescaler value + 1) / Division_factor )

　　通过tiny4412用户手册我们可以找到看门狗的中断号为75（如下图）：

　　预分频器Prescaler及分频因子Division factor的值在WTCON（看门狗时钟控制寄存器)中设置，如下图：

　　今天的程序是使用watchdog来实现led灯的闪烁，下面贴出代码：

 1 #ifndef __BUNFLY_H

 2 #define __BUNFLY_H

 3 

 4 #define ICCICR_CPU0        (*(volatile unsigned long *)0x10480000)

 5 #define ICCPMR_CPU0        (*(volatile unsigned long *)0x10480004)

 6 #define ICDDCR            (*(volatile unsigned long *)0x10490000)

 7 #define ICDIPR0_CPU0    (*(volatile unsigned long *)0x10490400)

 8 #define ICDIPTR0_CPU0    (*(volatile unsigned long *)0x10490800)

 9 #define ICDISER0_CPU0    (*(volatile unsigned long *)0x10490100)

10 #define ICDSGIR            (*(volatile unsigned long *)0x10490f00)

11 #define ICCEOIR_CPU0    (*(volatile unsigned long *)0x10480010)

12 #define ICCIAR_CPU0        (*(volatile unsigned long *)0x1048000c)

13 #define ICDIPR2_CPU0    (*(volatile unsigned long *)0x10490408)

14 #define ICDIPTR2_CPU0    (*(volatile unsigned long *)0x10490808)

15 #define ICDIPR3_CPU0    (*(volatile unsigned long *)0x1049040c)

16 #define ICDIPTR3_CPU0    (*(volatile unsigned long *)0x1049080c)

17 #define ICDIPR16_CPU0    (*(volatile unsigned long *)0x10490440)

18 #define ICDIPTR16_CPU0    (*(volatile unsigned long *)0x10490840)

19 #define ICDIPR18_CPU0    (*(volatile unsigned long *)0x10490448)

20 #define ICDIPTR18_CPU0    (*(volatile unsigned long *)0x10490848)

21 #define ICDISER2_CPU0    (*(volatile unsigned long *)0x10490108)

22 

23 #define WTCON             (*(volatile unsigned long *)0x10060000)

24 #define WTDAT             (*(volatile unsigned long *)0x10060004)

25 #define WTCNT             (*(volatile unsigned long *)0x10060008)

26 #define WTCLRINT         (*(volatile unsigned long *)0x1006000C)

27 

28 #define EXT_INT43CON    (*(volatile unsigned long *)0x11000e0c)

29 #define EXT_INT43_MASK    (*(volatile unsigned long *)0x11000f0c)

30 #define EXT_INT43_PEND    (*(volatile unsigned long *)0x11000f4c)

31 #define GPX3CON         (*(volatile unsigned long *)0x11000c60)

32 

33 #define GPM4CON    (*(volatile unsigned long *)0x110002e0)

34 #define GPM4DAT (*(volatile unsigned long *)0x110002e4)

35 

36 #endif    //__BUNFLY_H

  1 #include "bunfly.h"

  2 

  3 void (*udelay)(int) = 0xc3e25f90;

  4 int (*printf)(char *, ...) = 0xc3e114d8;

  5 void enable_mmu();

  6 void init_table(unsigned long *addr);

  7 void memcpy(unsigned char *dest, unsigned char *src, int len);

  8 extern unsigned long  vector_start;

  9 void do_irq();

 10 void led_on();

 11 void led_off();

 12 

 13 int main()

 14 {    

 15     memcpy(0x70000000, vector_start, 0x1000);    

 16     enable_mmu();

 17 

 18     *(unsigned long *)0x47000000 = do_irq;

 19 

 20     //step 1: set cpu permit interrupt

 21     __asm__ __volatile__(

 22         "mrs r0, cpsrn"

 23         "bic r0,r0, #0x80n"

 24         "msr cpsr, r0n"

 25         :::"r0"

 26     );

 27 

 28     //step 2: set GIC (cgi) enable

 29     ICCICR_CPU0 = 1; //中断总开关

 30     ICCPMR_CPU0 =0xff;//设置最低优先级（门槛）

 31     ICDDCR = 1; //本中断开关

 32     ICDIPR18_CPU0 = (100 << 24);//设置本中断优先级

 33     ICDIPTR18_CPU0 = (1 << 24);//选择指定的cpu进行中断处理

 34     ICDISER2_CPU0 = (1 << 11);//启用本中断

 35     

 36     //step 3: set watch dog timer

 37     WTCNT = 32768;

 38     WTDAT = 32768;

 39     WTCON = (1 << 2) | (3 << 3) | (1 << 5) | (95 << 8);

 40             

 41     printf("welcom backn");

 42 }

 43 

 44 void do_irq()

 45 {

 46     WTCLRINT = 0;//清中断

 47     printf("wang wang wangn");

 48     static int flags = 1;

 49     if(flags) {

 50         led_on();

 51         flags = 0;

 52     }

 53     else {

 54         led_off();

 55         flags = 1;

 56     }

 57 }

 58 

 59 void led_on()

 60 {

 61     GPM4CON &= ~0xffff;

 62     GPM4CON |= 0x1111;

 63     GPM4DAT &= ~0xf;

 64 }

 65 

 66 void led_off()

 67 {

 68 

 69     GPM4CON &= ~0xffff;

 70     GPM4CON |= 0x1111;

 71     GPM4DAT |= 0xf;

 72 }

 73 

 74 void memcpy(unsigned char *dest, unsigned char *src, int len)

 75 {

 76     int i = 0;

 77     for(i = 0; i < len; i++) {

 78         dest[i] = src[i];

 79     }

 80 }

 81 

 82 void enable_mmu()

 83 {

 84     /*构建表*/

 85     unsigned long addr = 0x50000000;

 86     init_table(addr);

 87     /*打开mmu*/

 88     unsigned long mmu = 0;

 89     mmu = 1 | (1 << 1) | (1 << 3) | (1 << 8);

 90     __asm__ __volatile__ (

 91         "mov r0, #3n"

 92         "MCR p15, 0, r0, c3, c0, 0n"//设置为管理员

 93         "MCR p15, 0, %0, c2, c0, 0n"//设置表的地址

 94         "MCR p15, 0, %1, c1, c0, 0n"//开启mmu

 95         :    

 96         :    "r" (addr), "r" (mmu)

 97         :

 98     );

 99 

100 }

101 

102 __asm__(

103 

104 "vector: n"

105 "    b resetn"

106 "    b undn"

107 "    b swin"

108 "    b pre_abtn"

109 "    b data_abtn"

110 "    .word 0x0n"

111 "    b irqn"

112 "    b fiqn"

113 "reset:n"

114 "und:n"

115 "    mov sp, #0x47000000n"

116 "    stmdb sp!, {r0-r12, lr}n"

117 

118 "    ldr r3, =0x47000004n"

119 "    ldr r2, [r3]n"

120 "    blx r2n"

121 

122 "    mov sp, #0x47000000n"

123 "    ldmdb sp, {r0-r12, pc}^    n"

124 

125 "swi:n"

126 "    mov sp, #0x47000000n"

127 "    stmdb sp!, {r0-r12, lr}^n"

128 

129 "    mov sp, #0x47000000n"

130 "    ldmdb sp, {r0-r12, pc}^    n"

131 

132 "pre_abt:n"

133 

134 "data_abt:n"

135 "    mov sp, #0x47000000n"

136 "    sub lr, lr, #4n"

137 "    stmdb sp!, {r0-r12, lr}n"

138 

139 "    ldr r3, =0x47000008n"

140 "    ldr r2, [r3]n"

141 "    blx r2n"

142 

143 "    mov sp, #0x47000000n"

144 "    ldmdb sp, {r0-r12, pc}^    n"

145 "irq:n"

146 

147 "    mov sp, #0x47000000n"

148 "    sub lr, lr, #4n"

149 "    stmdb sp!, {r0-r12, lr}n"

150 

151 "    ldr r3, =0x47000000n"

152 "    ldr r2, [r3]n"

153 "    blx r2n"

154 

155 "    mov sp, #0x47000000n"

156 "    ldmdb sp, {r0-r12, pc}^    n"

157 

158 "fiq:n"

159 

160     ".global vector_startn"

161 "vector_start: n"

162     ".word vector n "

163 

164 );

165 

166 void init_table(unsigned long *addr)

167 {

168     unsigned long va = 0;

169     unsigned long phys = 0;

170 

171     //0x40000000-0x80000000 -> 0x40000000-0x80000000    

172     for(va = 0x40000000; va < 0x80000000; va += 0x100000) {

173         phys = va;

174         addr[va >> 20] = phys | 2;

175     }

176 

177     //0x10000000-0x14000000 -> 0x10000000-0x140000000    

178     for(va = 0x10000000; va < 0x14000000; va += 0x100000) {