system_init.bak

IIC通信

void hdwinit( void )  //PM == 0 output
{						                 
	DI();
	IMS = MEMORY_IMS_SET;    
	IXS = MEMORY_IXS_SET;
										// Clock operation port mode (OSCCTL register)
	AMPH   = 0;       // select the external Clock frequency range(4MHz < fXH <= 10MHz)
    EXCLK  = 0;       //select the externa High-speed system clock operation mode(fX or fEXCLK or STOP)
    OSCSEL = 1;                         // External resonator connected to fX1 and fX2 input
	EXCLKS = 0;                         //(fXT or fEXCLKS or STOP)
	OSCSELS = 0;						// XT1 stop working
	
	// (permit) High-speed input clock operating (X1)
    MOC  = 0x00;                        
                                        // 00000000 = 0x00
                                        // |-------   High-speed input clock operation
                                        // |-------   --------------------------------
                                        // |-------   fXH input clock             | External clock input
                                        // |-------   ----------------------------+-------------------------
                                        // 0 -------- fXH input clock oscillating | External clock operating
                                        // 1 -------- fXH input clock stopped     | External clock stopped

// Check Oscillation stabilization time status

//waiting for the X1 clock oscillation stabilization time 
//--------------------------------------------
// The necessary oscillation stabilization time must be known beforehand.
// Pls. refer to the DS or UM of the oscillator manufacturer.
    while(OSTC < 0x1f)                  // Wait until fXH clock stabilization
    {                                   // time has been elapsed

        //----------------------------------------------------------
        // During X1 oscillation stabilization time status check
        // some other initializations, e.g. ports, can be done,
        // dependent on the needed X1 oscillation stabilization time
        // 102.4祍...3.28ms @ 20MHz
        //----------------------------------------------------------

        NOP();
    }

  //Oscillation stabilization time after STOP mode release
  //The wait time set by OSTS is valid only after the STOP mode is released with the X1 clock selected as the CPU clock. 
    OSTS = 0x01;                        // 512us@4MHz wait after STOP mode release (RESET value)
                                        // 00000101 = 0x05
                                        // -----|||   Osc. stabilization time
                                        // -----|||   -----------------------
                                        // -----001 - 2^11/fx
                                        // -----010 - 2^13/fx
                                        // -----011 - 2^14/fx
                                        // -----100 - 2^15/fx
                                        // -----101 - 2^16/fx
                                        // -----other settings prohibited



//This register is used to select the CPU clock and the division ratio
//---------------------------------------------
    PCC  = 0x00;                        // Use high speed mode fCPU = 4MHz
                                        // 00000000 = 0x00
                                        // -----|||   CPU clock selection fCPU
                                        // -----|||   ------------------------
                                        // -----000 - fx
                                        // -----001 - fx/2
                                        // -----010 - fx/2^2
                                        // -----011 - fx/2^3
                                        // -----100 - fx/2^4
                                        // -----other settings prohibited


// selects the main system clock supplied to CPU clock and clock supplied to peripheral hardware clock. 
//-----------------------------------------------------------------
// The maximum time required to switch between ring oscillator clock and
// fXH clock is 2 clocks

 // fXH clock supplied to the peripherals
    XSEL = 1;                         

    do
    {
        MCM0 = 1;                       // fXH clock supplied to CPU
                                        // 00000001 = 0x01
                                        // -----|||   CPU clock status
                                        // -----|||   ----------------
                                        // -----||0 - Operates with ring oscillator clock
                                        // -----||1 - Operates with X1 input clock
                                        // -----||
                                        // -----||    Selection of clock supplied to CPU and peripherals
                                        // -----||    --------------------------------------------------
                                        // -----00 -- fCPU = fRH / fPRS = fRH
                                        // -----01 -- fCPU = fRH / fPRS = fRH
                                        // -----10 -- fCPU = fRH / fPRS = fXH
                                        // -----11    fCPU = fXH / fPRS = fXH <---
                                        //      |
                                        //      +---- XSEL

    }
   while(MCS != 1);                    // Check if CPU operates with fXH clock( bit MCS IS read-only)
                                        // If no  => Retry to switch CPU clock
                                        // If yes => continue

// Switch off the high-speed and the low-speed Ring-OSC
//-----------------------------------------------------
// select the operation mode of internal oscillator  (all stop) 
    RCM  = 0x01;                        // High-speed Ring-OSC oscillating
                                        // High-speed Ring-OSC low accuracy (stop)
                                        // Low-speed Ring-OSC oscillating (stop)
                                        // 00000000 = 0x00
                                        // |-----||   High-speed Ring-OSC operation
                                        // |-----||   -----------------------------
                                        // |-----|0 - High-speed Ring-OSC oscillating
                                        // |-----|1 - High-speed Ring-OSC stopped
                                        // |-----|
                                        // |-----|    Low-speed Ring-OSC operation
                                        // |-----|    ----------------------------
                                        // |-----0 -- Low-speed Ring-OSC oscillating
                                        // |-----1 -- Low-speed Ring-OSC stopped
                                        // |
                                        // |          High-speed Ring-OSC accuracy status
                                        // |          -----------------------------------
                                        // 0 -------- High-speed Ring-OSC low accuracy
                                        // 1 -------- High-speed Ring-OSC high accuracy
	EI();
}

void Lvi_Init( void )
{
	LVIMK = 1;					//disable LVI interrupt
	LVISEL = 0;					//Detect level of supply voltage
	LVIS = 0X02;				//detection voltage level:3.93V
	//LVIIF = 0;
	//LVIMK = 0;
	//LVIPR = 1;
	LVIMD = 0;					//generates intenal reset when the level is detected
	LVION = 1;					//enable LVI operation
}