/* ****************TxFifo.c********
   Pointer implementation of the transmit 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
*/

char *TxPutPt;    /* Pointer of where to put next */
char *TxGetPt;    /* Pointer of where to get next */
                  /* FIFO is empty if PutPt=GetPt */
                  /* FIFO is full  if PutPt+1=GetPt */
char TxFifo[TxFifoSize];     /* The statically allocated fifo data */

/*-----------------------TxInitFifo----------------------------
  Initialize fifo to be empty
  Inputs: none
  Outputs: none */
void TxInitFifo(void){
 TxPutPt=TxGetPt=&TxFifo[0];   /* Empty when PutPt=GetPt */
}

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