p8251.c

mips架构的bootloader,99左右的版本 但源代码现在没人更新了

/*************************************************************
 * File: lib/p8251.c
 * Purpose: Part of C runtime library
 * Author: Phil Bunce ([e-mail])
 * Revision History:
 *	970304	Start of revision history
 *	980618	Added OP_BAUDRATES
 */

#include <mips.h>
/* 
 * Polled I/O routines for the LSI 8251-compatable MegaCore 
 *
 * Because the registers for these devices are scattered all over the
 * address map, I have created a pseudo device L8251rec that contains
 * all the information for a channel. Each chip that uses this device
 * has an array of these structures (eg. l08_sio for the 64008).
 *
 * Each 8251 has the following registers:
 *
 *	SIOAn	Attribute Register
 *	SIOMn	Mode Register
 *	SIOBn	Baudrate Register (write only)
 *	SIODn	Data Register
 *	SIOCn	Command (write only)
 *	SIOSn	Status Register (read only)
 */

#include <terms.h>
#include <utypes.h>


#ifdef LR64008
/* This is the pseudo device for the L64008 */
L8251rec l08_sio[] = {
	{M_08_SIOA1,M_08_SIOM1,M_08_SIOB1,M_08_SIOD1,M_08_SIOC1,M_08_SIOS1},
	{M_08_SIOA2,M_08_SIOM2,M_08_SIOB2,M_08_SIOD2,M_08_SIOC2,M_08_SIOS2},
	{M_08_SIOA0,M_08_SIOM0,M_08_SIOB0,M_08_SIOD0,M_08_SIOC0,M_08_SIOS0},
	{0}};
#endif


/* btab = sysclk/(baudrate*N)  */
/* assumes a sysclk of 27 MHz  and N=16 */
static long btab[] = {
	-1, 	/* B0 */
	33750,	/* B50 */
	22500,	/* B75 */
	15340,	/* B110 */
	12593,	/* B134 */
	11250,	/* B150 */
	8437,	/* B200 */
	5625,	/* B300 */
	2813,	/* B600 */
	1406,	/* B1200 */
	937,	/* B1800 */
	703,	/* B2400 */
	352,	/* B4800 */
	176,	/* B9600 */
	88,	/* B19200 */
	44,	/* B38400 */
	0	/* end */
	};

#define DEFRATE		13 /* default baudrate (9600) */

#define inb(a)      (*((volatile Uchar *)(a)))
#define inh(a)      (*((volatile Ushort *)(a)))
#define outb(a,v)      (*((volatile Uchar *)(a))=(v))
#define outh(a,v)      (*((volatile Ushort *)(a))=(v))
#define outw(a,v)      (*((volatile Ulong *)(a))=(v))

#define TXEMPTY 0x03  
#define RXRDY	0x02
#define TXRDY	0x01

/*************************************************************
*  p8251(op,siodat,chan,ch)
*/
p8251(op,siodat,chan,ch)
int op,chan,ch;
struct p8251info *siodat;
{
int i,brate;
L8251rec *p;
Ulong m,v;

p = (L8251rec *) l08_sio; /* siodat->siobase; we have one 8251 only anyhow */
switch (op) {
	case OP_RXRDY : 
		if (inb(p[chan].status)&RXRDY) return(1);
		break;

	case OP_RX :
		return inb(p[chan].data);

	case OP_TXRDY :
		if (inb(p[chan].status)&TXRDY) return(1);
		break;

	case OP_TX :
		outb(p[chan].data,ch);
		break;

	case OP_INIT : 
		for (i=0;p[i].attribute;i++) {
			outh(p[i].attribute,5);  /* 16-bit */
			/* mode: 2 stopbits, no parity, 8 bitsdata, 16x */
			if (inh(p[i].baudrate) == 0xffff) 
				outh(p[i].mode,0x4e00);
			outh(p[i].baudrate,btab[DEFRATE]);
			/* cmd: enable rx & tx */
			outb(p[i].cmd,0x27); 
			}
		break;
	case OP_BAUD : 
		brate = ch;
		/* check brate <= 15 */
		if (brate > 15) return(1); /* baud rate too large */
		/* return if unsupported baud rate */
		if (btab[brate] == -1) return(1);  
		outh(p[chan].baudrate,btab[brate]);
		break;
	case OP_CLKINIT : break;
	case OP_DELAY : return(0); break;
	case OP_BAUDRATES :
		m = 1;
		for (i=v=0;btab[i];i++) {
			if (btab[i] != -1) v |= m;
			m <<= 1;
			}
		return(v);
		break;
	}
return(0);
}