/* ****************RxFifo.c********
   Pointer implementation of the receive FIFO for the MC68HC11EVB

   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
*/

/* Number of characters in the Fifo
     the FIFO is full when it has FifoSize-1 characters */
char *RxPutPt;    /* Pointer of where to put next */
char *RxGetPt;    /* Pointer of where to get next */
                  /* FIFO is empty if PutPt=GetPt */
                  /* FIFO is full  if PutPt+1=GetPt */
char RxFifo[RxFifoSize];     /* The statically allocated fifo data */

/*-----------------------RxInitFifo----------------------------
  Initialize fifo to be empty
  Inputs: none
  Outputs: none */
void RxInitFifo(void){
 RxPutPt=RxGetPt=&RxFifo[0];   /* Empty when PutPt=GetPt */
}

/*-----------------------RxPutFifo----------------------------
  Enter one character into the fifo
  Inputs: 8 bit data
  Outputs: true if data is properly saved
  Since this is called by interrupt handlers no sei,cli*/
int RxPutFifo(char data){
char *tempPt;
   tempPt=RxPutPt;
   *(tempPt++)=data;  /* try to Put data into fifo */
   if (tempPt==&RxFifo[RxFifoSize]) /* need to wrap?*/
      tempPt = &RxFifo[0];
   if (tempPt == RxGetPt ){
      return(0);    /* Failed, fifo was full */
   }     
   else{
      RxPutPt=tempPt;     /* Success, so update pointer */
      return(1);
   }
}
/*-----------------------RxGetFifo----------------------------
  Remove one character from the fifo
  Inputs: pointer to place to save 8 bit data
  Outputs: true if data is valid */
int RxGetFifo(char *datapt){
   if (RxPutPt == RxGetPt )
      return(0);     /* Empty if PutPt=GetPt */
   else{
      asm(" sei");  /* make atomic, called by main thread */
      *datapt=*(RxGetPt++);
      if (RxGetPt==&RxFifo[RxFifoSize]) 
          RxGetPt = &RxFifo[0];
      asm(" cli");  /* end critical section */
      return(1); }
}