ti和motorola的spi协议有什么区别

最大的区别是SPI是4线（时钟，两个数据线，片选线）或者3线（时钟，两个数据线）的，I2C是两线的（时钟，一个数据线）。一般SPI的速度比I2C快很多，因为它有两个数据线的所以可以实现全双工通讯，而I2C因为收发共用一根数据线，所以只能是半双工的。

实现软件锁相环技术的方法很多，如指针归零同时调频调相[1]、多周期调节锁相原理[2]等。上述方法、 法利用DSP的捕获单元，对单相电压的过零点进行捕获，只能在电压过零点时，对相位进行校正。若在一个周期内相位发生变化

stc spi的例程

#include "reg51.h"

#define FOSC18432000L

#define BAUD(256 - FOSC / 32 / 115200)

typedef unsigned char BYTE

typedef unsigned int WORD

typedef unsigned long DWORD

sfr AUXR = 0x8e //Auxiliary register

sfr SPSTAT = 0xcd //SPI status register

#define SPIF0x80//SPSTAT.7

#define WCOL0x40//SPSTAT.6

sfr SPCTL = 0xce //SPI control register

#define SSIG0x80//SPCTL.7

#define SPEN0x40//SPCTL.6

#define DORD0x20//SPCTL.5

#define MSTR0x10//SPCTL.4

#define CPOL0x08//SPCTL.3

#define CPHA0x04//SPCTL.2

#define SPDHH 0x00//CPU_CLK/4

#define SPDH0x01//CPU_CLK/16

#define SPDL0x02//CPU_CLK/64

#define SPDLL 0x03//CPU_CLK/128

sfr SPDAT = 0xcf //SPI data register

sbit SPISS = P1^3 //SPI slave select, connect to other MCU's SS(P1.4) pin

sfr IE2 = 0xAF //interrupt enable rgister 2

#define ESPI0x02//IE2.1

void InitUart()

void InitSPI()

void SendUart(BYTE dat) //send data to PC

BYTE RecvUart() //receive data from PC

bit MSSEL //1: master 0:slave

///////////////////////////////////////////////////////////

void main()

{

InitUart()//initial UART

InitSPI() //initial SPI

IE2 |= ESPI

EA = 1

while (1)

{

if (RI)

{

SPCTL = SPEN | MSTR//set as master

MSSEL = 1

ACC = RecvUart()

SPISS = 0 //pull low slave SS

SPDAT = ACC//trigger SPI send

}

}

}

///////////////////////////////////////////////////////////

void spi_isr() interrupt 9 using 1 //SPI interrupt routine 9 (004BH)

{

SPSTAT = SPIF | WCOL //clear SPI status

if (MSSEL)

{

SPCTL = SPEN //reset as slave

MSSEL = 0

SPISS = 1 //push high slave SS

SendUart(SPDAT) //return received SPI data

}

else

{ //for salve (receive SPI data from master and

SPDAT = SPDAT // send previous SPI data to master)

}

}

///////////////////////////////////////////////////////////

void InitUart()

{

SCON = 0x5a //set UART mode as 8-bit variable baudrate

TMOD = 0x20 //timer1 as 8-bit auto reload mode

AUXR = 0x40 //timer1 work at 1T mode

TH1 = TL1 = BAUD //115200 bps

TR1 = 1

}

///////////////////////////////////////////////////////////

void InitSPI()

{

SPDAT = 0 //initial SPI data

SPSTAT = SPIF | WCOL //clear SPI status

SPCTL = SPEN //slave mode

}

///////////////////////////////////////////////////////////

void SendUart(BYTE dat)

{

while (!TI) //wait pre-data sent

TI = 0//clear TI flag

SBUF = dat//send current data

}

///////////////////////////////////////////////////////////

BYTE RecvUart()

{

while (!RI) //wait receive complete

RI = 0//clear RI flag

return SBUF //return receive data

}

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