// Chapter 7 6805 C programs// Jonathan W. Valvano// This software accompanies the book,// Embedded Microcomputer Systems: Real Time Interfacing// published by Brooks Cole, 1999// Program 7.19. C language initialization for a D/A interface using the SPI.// MC68HC05C8void DACInit(void){ // PD5=LD=1   DDRD|=0x38;  // PD4=CLK=SPI clock out   PORTD|=0x20; // PD3=SRI=SPI master out/* bit SPCR 7 SPIE = 0   no interrupts 6 SPE  = 1   enable SPI 4 MSTR = 1   master 3 CPOL = 0   output changes on fall,  2 CPHA = 0   clock normally low 1 SPR1 = 0   1 MHz operation 0 SPR0 = 0    */   SPCR=0x50;}// Program 7.20. C language function for a D/A interface using the SPI.// MC68HC05C8#define SPRF 0x80void DACout(unsigned int code){ unsigned char dummy;   SPDR=0x00FF &(code>>8); // msbyte   while((SPSR&SPIF)==0); // gadfly wait    dummy=SPDR;            // clear SPIF   SPDR=0x00FF& code;     // lsbyte   while((SPSR&SPIF)==0); // gadfly wait    dummy=SPDR;            // clear SPIF   PORTD &= ~0x20;         // PD5=LD=0// Program 7.21. C language initialization for an A/D interface using the SPI.// MC68HC05C8void ADCInit(void){ // PD5=CS=1   DDRD|=0x38;  // PD4=SCLK=SPI clock out   PORTD|=0x20; // PD3=DIN=SPI master out/* bit SPCR        PD2=DOUT=SPI master in 7 SPIE = 0   no interrupts 6 SPE  = 1   enable SPI 4 MSTR = 1   master 3 CPOL = 0   output changes on fall,  2 CPHA = 0   clock normally low 1 SPR1 = 0   1 MHz operation 0 SPR0 = 0    */   SPCR=0x50;} #define CH0 0x9F#define CH1 0xDF#define CH2 0xAF#define CH3 0xEF// Program 7.22. C language function for an A/D interface using the SPI.// MC68HC05C8unsigned int ADCin(unsigned char code){  unsigned int data;   PORTD &= ~0x20; // PD5=CS=0   SPDR=code;    // set channel,mode   while((SPSR&0x80)==0); // gadfly wait    data=SPDR;    // clear SPIF   SP0DR=0;       // start SPI   while((SPSR&0x80)==0); // gadfly wait    data=SPDR<<8; // msbyte of A/D   SPDR=0;       // start SPI   while((SPSR&0x80)==0); // gadfly wait    data+=SPDR;    // lsbyte of A/D   PORTD |= 0x20; // PD5=CS=1   return data>>3;} // right justify// Program 7.23. C language initialization of a temperature sensor interface using the SPI.// MC68HC812A4/MC68HC912B32 only// Program 7.24. C language helper functions for a temperature sensor interface using the SPI.// MC68HC812A4/MC68HC912B32 only// Program 7.25. C language functions for a temperature sensor interface using the SPI.// MC68HC812A4/MC68HC912B32 only