Exynos4412裸機開發 —— RTC 實時時鐘單元
阿新 • • 發佈:2019-01-05
RTC(Real-Time Clock) 實時時鐘。RTC是積體電路,通常稱為時鐘晶片。在一個嵌入式系統中,通常採用RTC來提供可靠的系統時間,包括時分秒和年月日等,而且要求在系統處於關機狀態下它也能正常工作(通常採用後備電池供電)。它的外圍也不需要太多的輔助電路,典型的就是隻需要一個高精度的32.768kHz 晶體和電阻電容等。
一、RTC 控制器
實時時鐘(RTC)單元可以通過備用電池供電,因此,即使系統電源關閉,它也可以繼續工作。RTC可以通過STRB/LDRB 指令將8位BCD碼資料送至CPU。這些BCD資料包括秒、分、時、日期、星期、月和年。RTC單元通過一個外部的32.768kHz 晶振提供時鐘。RTC具有定時報警的功能。
其功能說明如下:
1 -- 時鐘資料採用BCD編碼。
2 -- 能夠對閏年的年月日進行自動處理。
3 -- 具有告警功能,當系統處於關機狀態時,能產生警告中斷。
4 -- 具有獨立的電源輸入。
5 -- 提供毫秒級時鐘中斷,該中斷可以用於作為嵌入式作業系統的核心時鐘。
二、RTC 控制器暫存器詳解
1 、Time Tick Generator
下面是示例程式:
標頭檔案定義:
/**********************************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程式如下:
#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; /* * 裸機程式碼,不同於LINUX 應用層, 一定加迴圈控制 */ void do_irq(void) { static int a = 1; int irq_num; irq_num = CPU0.ICCIAR&0x3ff; //獲取中斷號 switch(irq_num) { case 57: printf("in the irq_handler\n"); EXT_INT41_PEND = EXT_INT41_PEND |((0x1 << 1)); //清GPIO中斷標誌位 ICDICPR.ICDICPR1 = ICDICPR.ICDICPR1 | (0x1 << 25); //清GIC中斷標誌位 break; case 76: printf("in the alarm interrupt!\n"); RTCINTP = RTCINTP | (1 << 1); ICDICPR.ICDICPR2 = ICDICPR.ICDICPR2 | (0x1 << 12); //清GIC中斷標誌位 break; case 77: printf("in the tic interrupt!\n"); RTCINTP = RTCINTP | (1 << 0); ICDICPR.ICDICPR2 = ICDICPR.ICDICPR2 | (0x1 << 13); //清GIC中斷標誌位 break; } CPU0.ICCEOIR = CPU0.ICCEOIR&(~(0x3ff))|irq_num; //清cpu中斷標誌位 } 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); //使能相應中斷到分配器 ICDIPTR.ICDIPTR19 = ICDIPTR.ICDIPTR19 & (~(0xff << 8))|(0x1 << 8); //選擇CPU介面 CPU0.ICCPMR = 255; //中斷遮蔽優先順序 CPU0.ICCICR = 1; //使能中斷到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); //使能相應中斷到分配器 ICDIPTR.ICDIPTR19 = ICDIPTR.ICDIPTR19 & (~(0xff << 0))|(0x1 << 0); //選擇CPU介面 CPU0.ICCPMR = 255; //中斷遮蔽優先順序 CPU0.ICCICR = 1; //使能中斷到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; }
執行結果如下:
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!