RTC(Real-Time Clock) 实时时钟。RTC是集成电路，通常称为时钟芯片。在一个嵌入式系统中，通常采用RTC来提供可靠的系统时间，包括时分秒和年月日等，而且要求在系统处于关机状态下它也能正常工作（通常采用后备电池供电）。它的外围也不需要太多的辅助电路，典型的就是只需要一个高精度的32.768kHz 晶体和电阻电容等。
一、RTC 控制器
实时时钟（RTC）单元可以通过备用电池供电，因此，即使系统电源关闭，它也可以继续工作。RTC可以通过STRB/LDRB 指令将8位BCD码数据送至CPU。这些BCD数据包括秒、分、时、日期、星期、月和年。RTC单元通过一个外部的32.768kHz 晶振提供时钟。RTC具有定时报警的功能。
其功能说明如下：
1 -- 时钟数据采用BCD编码。
2 -- 能够对闰年的年月日进行自动处理。
3 -- 具有告警功能，当系统处于关机状态时，能产生警告中断。
4 -- 具有独立的电源输入。
5 -- 提供毫秒级时钟中断，该中断可以用于作为嵌入式操作系统的内核时钟。
二、RTC 控制器寄存器详解
1 、Time Tick Generator
下面是示例程序：
头文件定义：
[cpp] view plaincopy 
- /**********************************RTC independ register********************************/
- #define RTCINTP __REG(0X10070030)
- #define RTCCON __REG(0X10070040)
- #define TICCNT __REG(0X10070044)
- #define CURTICCNT __REG(0X10070090)
- typedef struct {
- unsigned int ALM;
- unsigned int SEC;
- unsigned int MIN;
- unsigned int HOUR;
- unsigned int DAY;
- unsigned int MON;
- unsigned int YEAR;
- }rtclam;
- #define RTCALM (* (volatile rtclam *)0X10070050)
- typedef struct {
- unsigned int BCDSEC;
- unsigned int BCDMIN;
- unsigned int BCDHOUR;
- unsigned int BCDWEEK;
- unsigned int BCDDAY;
- unsigned int BCDMON;
- unsigned int BCDYEAR;
- }rtcbcd;
- #define RTC (* (volatile rtcbcd *)0X10070070)
C程序如下：
[cpp] view plaincopy
- #include "exynos_4412.h"
- void mydelay_ms(int time)
- {
- int i, j;
- while(time--)
- {
- for (i = 0; i < 5; i++)
- for (j = 0; j < 514; j++);
- }
- }
- //*(volatile unsigned int *)(0x11000c20) = 0;
- /*
- * 裸机代码，不同于LINUX 应用层， 一定加循环控制
- */
- void do_irq(void)
- {
- static int a = 1;
- int irq_num;
- irq_num = CPU0.ICCIAR&0x3ff; //获取中断号
- switch(irq_num)
- {
- case 57:
- printf("in the irq_handler\n");
- EXT_INT41_PEND = EXT_INT41_PEND |((0x1 << 1)); //清GPIO中断标志位
- ICDICPR.ICDICPR1 = ICDICPR.ICDICPR1 | (0x1 << 25); //清GIC中断标志位
- break;
- case 76:
- printf("in the alarm interrupt!\n");
- RTCINTP = RTCINTP | (1 << 1);
- ICDICPR.ICDICPR2 = ICDICPR.ICDICPR2 | (0x1 << 12); //清GIC中断标志位
- break;
- case 77:
- printf("in the tic interrupt!\n");
- RTCINTP = RTCINTP | (1 << 0);
- ICDICPR.ICDICPR2 = ICDICPR.ICDICPR2 | (0x1 << 13); //清GIC中断标志位
- break;
- }
- CPU0.ICCEOIR = CPU0.ICCEOIR&(~(0x3ff))|irq_num; //清cpu中断标志位
- }
- void rtc_init(void)
- {
- RTCCON = 1;
- RTC.BCDYEAR = 0x16;
- RTC.BCDMON = 0x2;
- RTC.BCDDAY = 0x25;
- RTC.BCDHOUR = 0x15;
- RTC.BCDMIN = 0x24;
- RTC.BCDSEC = 0x50;
- RTCCON = 0;
- }
- void rtc_tic(void)
- {
- RTCCON = RTCCON & (~(0xf << 4)) | (1 << 8);
- TICCNT = 32768;
- ICDDCR = 1; //使能分配器
- ICDISER.ICDISER2 = ICDISER.ICDISER2 | (0x1 << 13); //使能相应中断到分配器
- ICDIPTR.ICDIPTR19 = ICDIPTR.ICDIPTR19 & (~(0xff << 8))|(0x1 << 8); //选择CPU接口
- CPU0.ICCPMR = 255; //中断屏蔽优先级
- CPU0.ICCICR = 1; //使能中断到CPU
- }
- void rtc_alarm(void)
- {
- RTCALM.ALM = (1 << 6)|(1 << 0);
- RTCALM.SEC = 0x58;
- ICDDCR = 1; //使能分配器
- ICDISER.ICDISER2 = ICDISER.ICDISER2 | (0x1 << 12); //使能相应中断到分配器
- ICDIPTR.ICDIPTR19 = ICDIPTR.ICDIPTR19 & (~(0xff << 0))|(0x1 << 0); //选择CPU接口
- CPU0.ICCPMR = 255; //中断屏蔽优先级
- CPU0.ICCICR = 1; //使能中断到CPU
- }
- int main (void)
- {
- rtc_init();
- rtc_alarm();
- rtc_tic();
- while(1)
- {
- printf("%x %x %x %x %x BCDSEC = %x\n",RTC.BCDYEAR,
- RTC.BCDMON,
- RTC.BCDDAY,
- RTC.BCDHOUR,
- RTC.BCDMIN,RTC.BCDSEC);
- mydelay_ms(1000);
- }
- return 0;
- }
执行结果如下：
[cpp] view plaincopy
- 16 2 5 15 24 BCDSEC = 50
- in the tic interrupt!
- 16 2 5 15 24 BCDSEC = 51
- in the tic interrupt!
- 16 2 5 15 24 BCDSEC = 52
- in the tic interrupt!
- 16 2 5 15 24 BCDSEC = 53
- 16 2 5 15 24 BCDSEC = 53
- 16 2 5 15 24 BCDSEC = 54
- in the tic interrupt!
- 16 2 5 15 24 BCDSEC = 55
- in the tic interrupt!
- 16 2 5 15 24 BCDSEC = 56
- in the tic interrupt!
- in the alarm interrupt!
- 16 2 5 15 24 BCDSEC = 58
- in the tic interrupt!
- 16 2 5 15 24 BCDSEC = 59
- in the tic interrupt!
- 16 2 5 15 25 BCDSEC = 0
- in the tic interrupt!
- 16 2 5 15 25 BCDSEC = 1
- in the tic interrupt!
- 16 2 5 15 25 BCDSEC = 2
- in the tic interrupt!
- 16 2 5 15 25 BCDSEC = 3
- in the tic interrupt!
- 16 2 5 15 25 BCDSEC = 4
- in the tic interrupt!
- 16 2 5 15 25 BCDSEC = 5
- in the tic interrupt!
