/* ****************SFIFO.C********
   FIFO using semaphores

   This example accompanies the book
     "Embedded Microcomputer Systems: Real Time Interfacing", Brooks-Cole, copyright (c) 2000,
      Jonathan W. Valvano 7/6/99

   Interface between the TExaS simulator running a MC68HC11 EVB
      with ICC11 freeware compiler 
   TExaS Copyright 1999 by Jonathan W. Valvano 
   for more information about ICC11 
      see http://www.imagecraft.com
   You may use this file without restrictions
*/
   
unsigned int *PutPt;    /* Pointer of where to put next */
unsigned int *GetPt;    /* Pointer of where to get next */
/* FIFO is empty when Available is less than or equal to zero */
/* FIFO is full  when RoomLeft is less than or equal to zero */
int RoomLeft;  /* Semaphore counting empty spaces */
int Available; /* Semaphore counting data in fifo */
unsigned int Fifo[FifoSize];     /* The statically allocated fifo data */
void InitFifo(void) {
   RoomLeft=FifoSize-1;    /* Maximum storage capability */
   Available=0;            /* Initially empty */
   PutPt=GetPt=&Fifo[0];
}

void Put(unsigned int data) {
   Wait(&RoomLeft);
   asm(" sei");      /* read modify write nonreentrant code  */
   PORTC|=1;
   *(PutPt++)=data;  /* Put data into fifo  */
   if (PutPt==&Fifo[FifoSize]) PutPt = &Fifo[0];
   PORTC&=0xFE;
   asm(" cli");
   Signal(&Available);
}

unsigned int Get(void) { unsigned int data;
   Wait(&Available);
   asm(" sei");   /* read modify write nonreentrant code */
   PORTC|=2;
   data=*(GetPt++);
   if (GetPt==&Fifo[FifoSize]) GetPt = &Fifo[0];
   PORTC&=0xFD;
   asm(" cli");
   Signal(&RoomLeft);
   return(data);}