sci.c

pic16F877A的串口功能C语言软件

#include <htc.h>
#include "sci.h"

/* Routines for initialisation and use of the SCI
 * for the PIC processor.
 */

/* other options:
 * frame errors
 */

#define sci_PutNinth(bitnine)	(TX9D = bitnine?1:0;)

unsigned char
sci_Init(unsigned long int baud, unsigned char ninebits)
{
	int X;
	unsigned long tmp;
	
	/* calculate and set baud rate register */
	/* for asynchronous mode */
	tmp = 16UL * baud;
	X = (int)(FOSC/tmp) - 1;
	if((X>255) || (X<0))
	{
		tmp = 64UL * baud;
		X = (int)(FOSC/tmp) - 1;
		if((X>255) || (X<0))
		{
			return 1;	/* panic - baud rate unobtainable */
		}
		else
			BRGH = 0;	/* low baud rate */
	}
	else
		BRGH = 1;	/* high baud rate */
	SPBRG = X;	/* set the baud rate */

	SYNC = 0;	/* asynchronous */
	SPEN = 1;	/* enable serial port pins */
	CREN = 1;	/* enable reception */
	SREN = 0;	/* no effect */
	TXIE = 0;	/* disable tx interrupts */
	RCIE = 0;	/* disable rx interrupts */
	TX9  = ninebits?1:0;	/* 8- or 9-bit transmission */
	RX9  = ninebits?1:0;	/* 8- or 9-bit reception */
	TXEN = 1;	/* enable the transmitter */

	return 0;
}

void
sci_PutByte(unsigned char byte)
{
	while(!TXIF)	/* set when register is empty */
		continue;
	TXREG = byte;

	return;
}

unsigned char
sci_GetByte(void)
{
	while(!RCIF)	/* set when register is not empty */
		continue;

	return RCREG;	/* RXD9 and FERR are gone now */
}

unsigned char
sci_CheckOERR(void)
{
	if(OERR)	/* re-enable after overrun error */
	{
		CREN = 0;
		CREN = 1;
		return 1;
	}
	
	return 0;
}



unsigned char
sci_GetNinth(void)
{
	while(!RCIF)
		continue;
	
	return RX9D;	/* RCIF is not cleared until RCREG is read */
}

unsigned char
sci_GetFERR(void)
{
	while(!RCIF)
		continue;
	
	return FERR;	/* RCIF is not cleared until RCREG is read */
}