임베디드 OS 개발 프로젝트 CH7

In CH7, I will examine the timer hadware and the interrupt related to this.

RealviewPB uses SP804 Timer and my goal is to implement "delay()" using it.

To use a new hardware, fisrt to do is making a register struct.

레지스터

• timerxload register
  - This is a value used to reload to the counter at the next rising edge.

• timerxvalue register
  - This register decreases starting from the value of the timerxload register and invokes interrupt when its value be 0.

• Timercontrol register`

ypedef union TimerXControl_t
{
    uint32_t all;
    struct {
        uint32_t OneShot:1;     //0
        uint32_t TimerSize:1;   //1
        uint32_t TimerPre:2;    //3:2
        uint32_t Reserved0:1;   //4
        uint32_t IntEnable:1;   //5
        uint32_t TimerMode:1;   //6
        uint32_t TimerEn:1;     //7
        uint32_t Reserved1:24;  //31:8
    } bits;
} TimerXControl_t;

• 	- b0 : default(wrapping mode)

  • b1 : Timer off after an interrupt
• [1]: Timer size
  - b0 : 16 bits timer
  • b1 : 32 bits timer
• [3:2] : TimePre
  - Timer interval
  • b00 : a clock
  • b01 : 16 clocks
  • b10 : 256 clocks
• [5] : Interrupt Enable bit
  - b0 : disable
  • b1 : enable
• [6] : Mode bit
  - b0 : free running
  • b1 : Periodic
• [7] : enabla bit
  - b0 : timer disable
  • b1 : timer enable