basic.c

在Freescale HCS12中使用I2C总线源码

		{
			if(TxCompleteflag == SET) 			/* if the last byte has been transmitted */		
			{
				TxCompleteflag = CLEAR;			/* clear the ISR transmit complete flag */
				Iic.ibcr.byte = (IBEN|TXRX);	/* send stop signal (clear MSSL) */
				TxBufferemptyflag = SET;		/* set the non-ISR transmit buffer empty flag */
			}	
			else								/* last byte has not been transmitted */
			{	
				if(Iic.ibsr.bit.rxak == CLEAR)	/* if the slave acknowledged last transfer */
				{
					if(MasterRxFlag == SET)		/* if the last transfer was an address and master is now to Rx */
					{
						Iic.ibcr.bit.txrx = CLEAR; 		/* switch to Rx mode */
						dummyibdrRead = Iic.ibdr.byte;	/* dummy read of IBDR register */
					}
					else						/* last transfer was to instruct other slave to receive */
					{
						Iic.ibdr.byte = *TxPacketpositionptr;		/* write next byte to IBDR */
						if (TxPacketpositionptr == TxPacketendptr)	/* if the last data has been Tx'd */
						{
							TxCompleteflag = SET;	/* set the ISR transmit complete flag */
						}
						else					/* there is still data to be transmitted */
						{
							TxPacketpositionptr++;	/* move to next byte to Tx */
						}
					}
				}
				else							/* slave did not acknowledge last transfer */
				{
					Iic.ibcr.byte = (IBEN|TXRX);	/* send stop signal (clear MSSL) */
				}
			}
		}
		else									/* module is to receive data */
		{				
			if(RxPacketpositionptr == RxPacketendptr)/* if the last byte has been received */
			{
				Iic.ibcr.byte = (IBEN);			/* send stop signal (clear MSSL) */
				RxCompleteflag = SET;			/* set the ISR receive complete flag */
			}
			else								/* last byte has not been received yet */
			{
				if(RxPacketpositionptr == (RxPacketendptr - 1))	/* if the second last byte has been received */
				{
					Iic.ibcr.bit.txak = SET;	/* disable active low acknowledge bit (signal to slave to stop Tx) */
				}
				else							/* second last byte is still to be received */
				{								/* do nothing here */
				}
			}
			
			*RxPacketpositionptr = Iic.ibdr.byte;	/* read the data from the slave */
			
			if (RxCompleteflag == SET)	/* if the last byte of data has been received */
			{
				RxCompleteflag = CLEAR;		/* clear the ISR receive complete flag */
				RxBufferfullflag = SET;		/* set the receive buffer full flag */
			}
			else							/* there is still data to receive */	
			{
				RxPacketpositionptr++;		/* increment the Rx packet position pointer */
			}	
		}
	}						
	else										/* module is in slave mode */
	{
		if(Iic.ibsr.bit.ibal == SET)			/* if module is now in slave mode because arbitration has been lost */
		{
			Iic.ibsr.bit.ibal = 1;				/* reset the abritration flag */
			
			if(Iic.ibsr.bit.iaas == SET)		/* if this module has been addressed as slave */
			{
				if(Iic.ibsr.bit.srw == SET)		/* if module is to transmit */
				{
					Iic.ibcr.bit.txrx = SET; 				/* switch to Tx mode */
					Iic.ibdr.byte = *TxPacketpositionptr;	/* write next byte to IBDR */
					if(TxPacketpositionptr == TxPacketendptr)	/* if the last byte has been transmitted */
					{
						TxBufferemptyflag = SET;	/* raise transmit complete flag */
					}
					else						/* last byte has not been transmitted */
					{
						TxPacketpositionptr++;	/* move to next byte to Tx */
					}
				}
				else							/* module is to receive */
				{
					Iic.ibcr.bit.txrx = CLEAR; 		/* switch to Rx mode */
					dummyibdrRead = Iic.ibdr.byte;	/* dummy read of IBDR register */
				}
			}
			else								/* module has not been addressed as a slave */
			{									/* do nothing here */
			}
		}
		else									/* arbitration was not lost */
		{
			if(Iic.ibsr.bit.iaas == SET)		/* if this module has been addressed as slave */
			{
				if(Iic.ibsr.bit.srw == SET)		/* if module is to transmit */
				{
					Iic.ibcr.bit.txrx = SET; 	/* switch to Tx mode */
					Iic.ibdr.byte = *TxPacketpositionptr;	/* write next byte to IBDR */
					if(TxPacketpositionptr == TxPacketendptr)	/* if the last byte has been transmitted */
					{
						TxBufferemptyflag = SET;	/* raise transmit complete flag */
					}
					else						/* last byte has not been transmitted */
					{
						TxPacketpositionptr++;	/* move to next byte to Tx */
					}		
				}
				else							/* module is to receive */
				{
					Iic.ibcr.bit.txrx = CLEAR; 		/* switch to Rx mode */
					dummyibdrRead = Iic.ibdr.byte;	/* dummy read of IBDR register */
				}
			}
			else								/* module has not been addressed as slave */
			{
				if(Iic.ibcr.bit.txrx == SET)	/* if module is to transmit */
				{
					if(Iic.ibsr.bit.rxak == CLEAR)	/* if the slave acknowledged last transfer */
					{
						Iic.ibdr.byte = *TxPacketpositionptr;	/* write next byte to IBDR */
						if(TxPacketpositionptr == TxPacketendptr)	/* if the last byte has been transmitted */
						{
							TxBufferemptyflag = SET;	/* raise transmit complete flag */
						}
						else					/* last byte has not been transmitted */
						{
							TxPacketpositionptr++;	/* move to next byte to Tx */
						}
					}
					else						/* module is not to transmit */
					{	
						Iic.ibcr.bit.txrx = CLEAR; 	/* switch to Rx mode */
						dummyibdrRead = Iic.ibdr.byte;	/* dummy read of IBDR register */
					}
				}
				else							/* module is to receive data */
				{
					*RxPacketpositionptr = Iic.ibdr.byte;	/* read IBDR register and store in current buffer location */
					if(RxPacketpositionptr == RxPacketendptr)	/* if the last packet has been received */
					{
						RxBufferfullflag = SET;	/* set flag */
					}
					else						/* last packet has yet to be received */
					{
						RxPacketpositionptr++;	/* move to next byte to transmit */
					}
				}					
			}
		}
	}			
}
					
/******************************************************************************
Function Name	:	_dummyISR
Engineer		:	M.Gallop	
Date			:	25/07/01
Parameters		:	NONE
Returns			:	NONE
Notes			:	Interrupt service routine for unused interrupt vectors. 
******************************************************************************/
#pragma TRAP_PROC
void 
_dummyISR( void )
{				
    for(;;); 	/* endless cycle */                               
}

/* End of interrupt service routines  */
/* reset code segment to default */
#pragma CODE_SEG DEFAULT