2_wdt_timer_rtc.ppt

QA Thank You * Hi every baby This chapter will introduce WDT Timer RTC. * Based on the title of this chapter, the meeting flow will start from 24bit time, 19WDT and RTC with calendar. * Every series supports four sets of 24 bit up counting timer And based on different application, every timer includes independent clock source selection and prescale. List equation Besides, timer support three modes and introduce it later. * Support five kinds of clock source, and the high speed is 22Mhz or the low speed is 32khz. Besides, if selecting clock source is GPIO, the frequent is defined by external input signal. It will count rising edge. * Main block is 24-bit up counter. The count speed is controlled by clock source and prescale. If the number of up counter equals TCMPR, timer will generate reset up-counter signal or interrupt to do something. The equation is below. Besides, up-counter supports read back function. * There are three operation modes, one shot, periodic and toggle mode. Once TCMPR is set 100, you will find the 24-bit up counter count from 0 to 123 and produce a interrupt. This behavior only executes one time at one shot mode. If change to periodic mode, it will reset counter and repeat counting from 0 to 123 till software stop. If change to toggle mode, it will continuously count to maximum value and overflow to return to 0. * * * * * * * * * * * * * * * * 32.768KHZ的晶振产生时序电路基准信号。32.768kHz是RTC（实时时钟）晶振，用32.768是因为32768是2的15次幂，可以很方便的分频，很精确的得到一秒的计时。所有的RTC晶振一般都是32.768或是其倍频。 * * * * * * * * * NuMicro Cortex-M0WDT Timer RTC 议题 四组 24比特定时器 一个19比特看门狗定时器 实时时钟, 带日历 定时器特性 四组24比特上数(up-counting)定时器 每个定时器有4个时钟源可选和一个预分频器 超时周期 = (定时器输入时钟) * (8-bit 预分频 + 1) * (24-bit TCMP) 4种操作模式. one shot, periodic, toggle mode 和 auto-reload counting mode 定时器时钟源 Trigger source: TM0?PB8 , TM1?PB9 TM2?PB10 , TM3?PB11 定时器方块图 每4个定时器时钟更新一次 超时周期 = (定时器输入时钟) * (8-bit 预分频值 + 1) * (24-bit TCMP) TMAX = (1 / 12 MHz) * (28) * (224-1) ≒341.3 sec. TMIN = (1 / 12 MHz) * (1+1) * (2) ≒0.31