// Chapter 2 6805 C programs// Jonathan W. Valvano// This software accompanies the book,// Embedded Microcomputer Systems: Real Time Interfacing// published by Brooks Cole, 1999// Program 2.2. An inappropriate use of #define.#define size 10short data[size];void initialize(void){ short j   for(j=0;j<10;j++)      data[j]=0;};// Program 2.3. An appropriate use of #define.#define size 10short data[size];void initialize(void){ short j   for(j=0;j<size;j++)      data[j]=0;};// Program 2.4. 6805 C implementation of a Mealy Finite State Machine.const struct State{	unsigned char Time;    /* Time to wait in each state */	unsigned char Out[2];  /* Output if input=0,1 */	const struct State *Next[2]; /* Next state if input=0,1 */};typedef const struct State StateType;#define SA &fsm[0]#define SB &fsm[1]#define SC &fsm[2]#define SD &fsm[3]StateType fsm[4]={	{100,{0,0},{SB,SD}},	{100,{0,8},{SC,SA}},	{ 15,{0,0},{SB,SD}},	{ 15,{8,8},{SC,SD}}};void Wait(unsigned int delay){ int Endt;    Endt=TCNT+delay;             /* Time (125ns cycles) to wait */    while((Endt-(int)TCNT)>0);   /* wait */};void main(void){ StatePtr *Pt;  /* Current State */        unsigned char Input;   Pt=SA;                /* Initial State */   DDRC=0x08;            /* PortC bit3 is output */   while(1){      Wait(Pt->Time);       /* Time to wait in this state */      Input=PORTC<<7;       /* Input=0 or 1 */      PORTC=Pt->Out[Input]; /* Perform output for this state */      Pt=Pt->Next[Input];   /* Move to the next state */}};// Program 2.6. 6805 C implementation of a Moore Finite State Machine./* PortC bits 1,0 are input, Port B bits 1,0 are output */const struct State {	unsigned char Out;            /* Output to Port B */	unsigned int Time;            /* Time in 100 祍ec to wait in this state */	const struct State *Next[4];  /* Next state if input=0,1,2,3 */};typedef const struct State StateType;#define SA &fsm[0]#define SB &fsm[1]#define SC &fsm[2]StateType fsm[3]={	{0x01, 4000,{SB,SA,SB,SC}},  /* SA out=1, wait= 500usec, next states */	{0x02, 8000,{SC,SA,SB,SC}},  /* SB out=2, wait=1000usec, next states */	{0x03,16000,{SA,SA,SB,SA}}   /* SC out=3, wait=2000usec, next states */};void Wait(unsigned int delay){ int Endt;    Endt=TCNT+delay;             /* Time (125ns cycles) to wait */    while((Endt-(int)TCNT)>0);   /* wait */};void main(void){ StatePtr *Pt;  /* Current State */  unsigned char Input;   Pt=SA;               /* Initial State */  DDRC=0x00;           /* Make Port C inputs */  DDRB=0xFF;  while(1){    PORTB=Pt->Out;      /* Perform output for this state */    Wait(Pt->Time);     /* Time to wait in this state */    Input=PORTC&0x03;   /* Input=0,1,2,or 3 */    Pt=Pt->Next[Input]; /* Move to next state */  }};// Program 2.7: A median function that is not very portable.unsigned int Median(unsigned int u1,unsigned int u2,unsigned int u3){ unsigned int result;  printf("The inputs are %d, %d, %d.\n",u1,u2,u3);  if(u1>u2)    if(u2>u3)   result=u2;     // u1>u2,u2>u3       u1>u2>u3      else        if(u1>u3) result=u3;   // u1>u2,u3>u2,u1>u3 u1>u3>u2        else      result=u1;   // u1>u2,u3>u2,u3>u1 u3>u1>u2  else     if(u3>u2)   result=u2;     // u2>u1,u3>u2       u3>u2>u1      else        if(u1>u3) result=u3;   // u2>u1,u2>u3,u1>u3 u2>u1>u3        else      result=u1;   // u2>u1,u2>u3,u3>u1 u2>u3>u1  printf("The median is %d.\n",result);  return(result):}// Program 2.27: Empirical measurement of dynamic efficiency in C.unsigned short before,elasped;void main(void){   ss=100;   before=TCNT;   tt=sqrt(ss);   elasped=TCNT-before;}// Program 2.29. Another empirical measurement of dynamic efficiency in C.void main(void){// PB7 is connected to a scope   ss=100;   while(1){     PORTB |= 0x80;  // set PB7 high     tt=sqrt(ss);     PORTB &= ~0x80; // clear PB7 low   }}// Program 2.30: A time/position profile dumping into a data array.unsigned short time[100];unsigned short place[100];unsigned short n;void profile(unsigned short p){  time[n]=TCNT; // record current time  place[n]=p;  n++;}unsigned short sqrt(unsigned short s){ unsigned short t,oldt;  profile(0);  t=0;       // based on the secant method  if(s>0) {profile(1);     t=32;   // initial guess 2.0     do{profile(2);       oldt=t;  // calculation from the last iteration       t=((t*t+16*s)/t)/2;} // t is closer to the answer     while(t!=oldt);}    // converges in 4 or 5 iterations profile(3);  return t;} // Program 2.31: A time/position profile using two output bits.unsigned int sqrt(unsigned int s){ unsigned int t,oldt;  PORTB=0;  t=0;       // based on the secant method  if(s>0) {PORTB=1;     t=32;   // initial guess 2.0     do{PORTB=2;       oldt=t;  // calculation from the last iteration       t=((t*t+16*s)/t)/2;} // t is closer to the answer     while(t!=oldt);}    // converges in 4 or 5 iterations PORTB=3;  return t;}