第三十七天：Tiny驱动开发之看门狗中断

时间：2014-11-26 20:43:24 阅读：477 评论：0 收藏：0 [点我收藏+]

标签：des style blog http io ar color 使用 sp

1. 看门狗原理

Watchdog原理上就是一个定时器。定时器timer对时钟进行计数，当定时器溢出时，产生复位信号，使得整个系统复位。在程序或嵌入式系统中，需要定期的对看门狗timer进行复位重新计数，定时器不会溢出复位系统，从而保证系统的正常运行。当某种原因（例如干扰）引起程序跑飞或者进入死循环时，程序不能定期的复位看门狗timer, 计数溢出产生复位信号，导致系统复位。

设本系统程序完整运行一周期的时间是T1，看门狗的定时周期为T2，T2>T1，在程序运行一周期后就修改定时器的计数值，只要程序正常运行，定时器就不会溢出，若因为程序“跑飞”或者进入死循环，那么系统不能在T1时刻修改时间的计数值，一直计数直到T2时刻溢出，引发系统复位，使系统重新运行，从而起到监控作用。

从上面的解释中可以看出，Watchdog的作用就是为了防止系统因意外“跑飞”，导致整个系统瘫痪时，恢复(reset)系统运行。

2. Tiny4412看门狗控制

1)作为常规定时器使用，并且可以产生中断

2)作为看门狗定时器使用，期满时，它可以产生128个时钟周期的复位信号

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。

看门狗定时器计数值的计算公式如下：

1)输入到计数器的时钟周期

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

预分频器Prescaler及分频因子Division factor的值由用户在WTCON（看门狗时钟控制寄存器)中设置。

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2)看门狗的定时周期

T = 计数值（WTCNT初值-WTCNT当前值） * t_watchdog

WTCNT为看门狗数据寄存器，用来设置计数多少个时钟周期。乘以时钟周期就是定时的总时间了。

具体代码：

  1 #include "regs.h"
  2 
  3 int (*printf)(char *, ...) = 0xc3e114d8;
  4 
  5 void init_ttb(unsigned long *ttb);
  6 void enable_mmu(void);
  7 void memcpy(unsigned char *dest, unsigned char *source, int len);
  8 void do_irq();
  9 
 10 int main()
 11 {
 12 
 13     enable_mmu();
 14     *(unsigned long *)0x67000000 = do_irq;
 15     unsigned long source = 0;
 16     __asm__ __volatile__(
 17         "ldr %0, =vector_start\n"
 18         : "=r" (source)
 19     );
 20     memcpy(0, source, 0x1000);
 21     
 22     //step 1: set cpsr i bit
 23     __asm__ __volatile__(
 24         "mrs r0, cpsr\n"
 25         "bic r0, r0, #0x80\n"
 26         "msr cpsr, r0\n"
 27         ::: "r0"
 28     );
 29 
 30     //step 2: enable gic
 31     ICCICR_CPU0 = 1;//终端总开关
 32     ICCPMR_CPU0 = 0xff;//设置最低优先级
 33 
 34     ICDDCR = 1;
 35     ICDIPR18_CPU0 &= ~(0xff << 24);//设置本中断优先级
 36     ICDIPTR18_CPU0 &= ~(0xff << 24);// 选择指定的cpu0进行终端处理
 37     ICDIPTR18_CPU0 |= (1 << 24);// 选择指定的cpu0进行终端处理
 38     ICDISER2_CPU0 = (1 << 11);//设置本中断开启
 39 
 40     //step 3: open interrupt source
 41     GPM4CON = 0x1111;
 42 
 43     WTCON = 0 | (1 << 2) | (0 << 3 ) | (1 << 5) | (254 << 8);
 44     WTDAT = 0x4000;
 45     printf("send sgi\n");
 46 }
 47 
 48 void do_irq()
 49 {
 50     printf("watch dog \n");
 51     
 52     static unsigned long tmp = 0xf;
 53     GPM4DAT = ~tmp;
 54     tmp = GPM4DAT;
 55 
 56     WTCLRINT = 0x1;    
 57     
 58 }
 59 
 60 __asm__(
 61 "vector_start:\n"
 62     "b reset\n"
 63     "b undef\n"
 64     "b swi\n"
 65     "b pre_abt\n"
 66     "b data_abt\n"
 67     ".word 0x0\n"
 68     "b irq \n"
 69     "b fiq\n"
 70     "\n"
 71 "reset:\n"
 72 "undef:\n"
 73     "mov sp, #0x66000000\n"
 74     "stmfd sp!, {r0-r12, lr}\n"
 75     "\n"
 76     "mov r0, #0x67000000\n"
 77     "ldr r1, [r0]\n"
 78     "blx r1\n"
 79     "\n"
 80     "mov sp, #0x66000000\n"
 81     "ldmea sp, {r0-r12, pc}^\n"
 82 "swi:\n"
 83     "mov sp, #0x66000000\n"
 84     "stmfd sp!, {r0-r12, lr}\n"
 85     "\n"
 86     "mov r0, #0x67000000\n"
 87     "ldr r1, [r0]\n"
 88     "blx r1\n"
 89     "\n"
 90     "mov sp, #0x66000000\n"
 91     "ldmea sp, {r0-r12, pc}^\n"
 92     "\n"
 93 "pre_abt:\n"
 94 "data_abt:\n"
 95     "mov sp, #0x66000000\n"
 96     "sub lr, lr, #4\n"
 97     "stmfd sp!, {r0-r12, lr}\n"
 98     "\n"
 99     "mov r0, #0x67000000\n"
100     "ldr r1, [r0]\n"
101     "blx r1\n"
102     "\n"
103     "mov sp, #0x66000000\n"
104     "ldmea sp, {r0-r12, pc}^\n"
105 "irq:\n"
106     "mov sp, #0x66000000\n"
107     "sub lr, lr, #4\n"
108     "stmfd sp!, {r0-r12, lr}\n"
109     
110     "mov r0, #0x67000000\n"
111     "ldr r1, [r0]\n"
112     "blx r1\n"
113     
114     "mov sp, #0x66000000\n"
115     "ldmea sp, {r0-r12, pc}^\n"
116 "fiq:\n"
117 
118 );
119 
120 void init_ttb(unsigned long *ttb)
121 {
122     unsigned long va = 0;
123     unsigned long pa = 0;
124     
125     //00000000~10000000  -> 60000000~64000000
126     for(va=0x00000000; va<0x10000000; va+=0x100000){
127         pa = va + 0x60000000;
128         ttb[va >> 20] = pa | 2;
129     }
130     
131     //10000000~14000000  -> 10000000~14000000
132     for(va=0x10000000; va<0x14000000; va+=0x100000){
133         pa = va;
134         ttb[va >> 20] = pa | 2;
135     }
136 
137     //40000000~80000000  -> 40000000~80000000
138     for(va=0x40000000; va<0x80000000; va+=0x100000){
139         pa = va;
140         ttb[va >> 20] = pa | 2;
141     }
142 
143     //30000000~40000000  -> 50000000~60000000
144     for(va=0x30000000; va<0x40000000; va+=0x100000){
145         pa = va + 0x20000000;
146         ttb[va >> 20] = pa | 2;
147     }
148 }
149 
150 void enable_mmu(void)
151 {
152     unsigned long ttb = 0x70000000;
153     init_ttb(ttb);
154     unsigned long mmu = 0;
155     mmu = 1 | (1 << 3) | (1 << 8);
156     __asm__ __volatile__(
157         "mov r0, #3\n"
158         "mcr p15, 0, r0, c3, c0, 0\n" 
159         "mcr p15, 0, %0, c2, c0, 0\n" 
160         "mcr p15, 0, %1, c1, c0, 0\n" 
161         :
162         : "r" (ttb), "r" (mmu)
163     );
164 }
165 
166 void memcpy(unsigned char *dest, unsigned char *source, int len)
167 {
168     int i = 0;
169     for(i=0; i<len; i++)
170         dest[i] = source[i];
171 }

 1 #define gpiobase        0x11000000
 2 #define GPM4CON         (*(volatile unsigned long *)(gpiobase + 0x02E0)) 
 3 #define GPM4DAT         (*(volatile unsigned long *)(gpiobase + 0x02E4))
 4 #define GPX3CON         (*(volatile unsigned long *)(gpiobase + 0x0C60))
 5 #define GPX3DAT         (*(volatile unsigned long *)(gpiobase + 0x0C64))
 6 
 7 #define ICC 0x10480000
 8 
 9 #define ICCICR_CPU0     (*(volatile unsigned long *)(ICC + 0x0000)) 
10 #define ICCPMR_CPU0     (*(volatile unsigned long *)(ICC + 0x0004)) 
11 #define ICCBPR_CPU0     (*(volatile unsigned long *)(ICC + 0x0008)) 
12 #define ICCIAR_CPU0     (*(volatile unsigned long *)(ICC + 0x000C)) 
13 #define ICCEOIR_CPU0    (*(volatile unsigned long *)(ICC + 0x0010)) 
14 #define ICCRPR_CPU0     (*(volatile unsigned long *)(ICC + 0x0014)) 
15 #define ICCHPIR_CPU0    (*(volatile unsigned long *)(ICC + 0x0018)) 
16 #define ICCABPR_CPU0    (*(volatile unsigned long *)(ICC + 0x001C)) 
17 #define INTEG_EN_C_CPU0 (*(volatile unsigned long *)(ICC + 0x0040)) 
18 #define ICCIIDR         (*(volatile unsigned long *)(ICC + 0x00FC))
19 
20 #define ICD 0x10490000
21 
22 #define ICDDCR            (*(volatile unsigned long *)(ICD + 0x0000))
23 #define ICDICTR           (*(volatile unsigned long *)(ICD + 0x0004))
24 #define ICDIIDR           (*(volatile unsigned long *)(ICD + 0x0008))
25 #define ICDISR0_CPU0      (*(volatile unsigned long *)(ICD + 0x0080))
26 #define ICDISER0_CPU0     (*(volatile unsigned long *)(ICD + 0x0100))
27 #define ICDISER2_CPU0     (*(volatile unsigned long *)(ICD + 0x0108))
28 #define ICDICER0_CPU0     (*(volatile unsigned long *)(ICD + 0x0180))
29 #define ICDISPR0_CPU0     (*(volatile unsigned long *)(ICD + 0x0200))
30 #define ICDICPR0_CPU0     (*(volatile unsigned long *)(ICD + 0x0280))
31 #define ICDABR0_CPU0      (*(volatile unsigned long *)(ICD + 0x0300))
32 #define ICDIPR0_CPU0      (*(volatile unsigned long *)(ICD + 0x0400))
33 #define ICDIPR1_CPU0      (*(volatile unsigned long *)(ICD + 0x0404))
34 #define ICDIPR2_CPU0      (*(volatile unsigned long *)(ICD + 0x0408))
35 #define ICDIPR3_CPU0      (*(volatile unsigned long *)(ICD + 0x040C))
36 #define ICDIPR4_CPU0      (*(volatile unsigned long *)(ICD + 0x0410))
37 #define ICDIPR5_CPU0      (*(volatile unsigned long *)(ICD + 0x0414))
38 #define ICDIPR6_CPU0      (*(volatile unsigned long *)(ICD + 0x0418))
39 #define ICDIPR7_CPU0      (*(volatile unsigned long *)(ICD + 0x041C))
40 #define ICDIPR18_CPU0      (*(volatile unsigned long *)(ICD + 0x0448))
41 
42 #define ICDIPTR0_CPU0    (*(volatile unsigned long *)(ICD + 0x0800))
43 #define ICDIPTR1_CPU0    (*(volatile unsigned long *)(ICD + 0x0804))
44 #define ICDIPTR18_CPU0    (*(volatile unsigned long *)(ICD + 0x0848))
45 #define ICDSGIR        (*(volatile unsigned long *)(ICD + 0x0F00))
46 
47 
48 #define WTCON     (*(volatile unsigned long *)0x10060000) 
49 #define WTDAT    (*(volatile unsigned long *)0x10060004) 
50 #define WTCNT    (*(volatile unsigned long *)0x10060008) 
51 #define WTCLRINT (*(volatile unsigned long *)0x1006000C)

第三十七天：Tiny驱动开发之看门狗中断

标签：des style blog http io ar color 使用 sp

原文地址：http://www.cnblogs.com/linrong/p/4124829.html

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