z85230.c

一个mips虚拟机非常好代码,使用C++来编写的,希望大家多学学,

/****************************************************************************
 * $Id: z85230.c,v 1.1.1.1 2003/07/10 05:44:51 matthewc Exp $
 * Copyright (C) 1997, 1998 Kevin Elphinstone, Univeristy of New South
 * Wales.
 *
 * This file is part of the L4/MIPS micro-kernel distribution.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 ****************************************************************************/
#include "termio.h"
#include "z85230.h"

typedef struct zsccdev *zsccdp;

#define ZSCCCLK	14745600	 /* clock rate 14.7456 MHz */

#if 0
static const int zsccbrtc[] = {
    -1,
    BRTC (ZSCCCLK, 50),
    BRTC (ZSCCCLK, 75),
    BRTC (ZSCCCLK, 110),
    BRTC (ZSCCCLK, 134),
    BRTC (ZSCCCLK, 150),
    BRTC (ZSCCCLK, 200),
    BRTC (ZSCCCLK, 300),
    BRTC (ZSCCCLK, 600),
    BRTC (ZSCCCLK, 1200),
    BRTC (ZSCCCLK, 1800),
    BRTC (ZSCCCLK, 2400),
    BRTC (ZSCCCLK, 4800),
    BRTC (ZSCCCLK, 9600),
    BRTC (ZSCCCLK, 19200),
    BRTC (ZSCCCLK, 38400)};
#endif

static void
zsccputreg (volatile zsccdp dp, unsigned char reg, unsigned char val)
{
  if (reg != zWR0) {
      dp->ucmd = zWR0_REG | reg; 
      wbflush ();
  }
  dp->ucmd = val;
  wbflush ();
}

static unsigned char
zsccgetreg (volatile zsccdp dp, unsigned char reg)
{
  if (reg != zRR0) {
    dp->ucmd = zWR0_REG | reg;
    wbflush ();
  }
  return (dp->ucmd);
}

static int
zsccinit (volatile zsccdp dp)
{
    volatile zsccdp dpa, dpb;

    dpa = dp; dpb = dpa - 1;

    /* single read to get in known state */
    (void) dpa->ucmd;
    (void) dpb->ucmd;

    /* global initialisation */
    
    zsccputreg(dpa, zWR9, zWR9_HARDRESET);

    return 0;
}


static void
zsccflush (volatile zsccdp dp)
{
    /* wait for Tx fifo to drain */
    int timeout = 10;
    while (!(zsccgetreg (dp, zRR0) & zRR0_TXEMPTY))
	if (--timeout == 0)
	    break;
}


static int
zsccprogram (volatile zsccdp dp, int baudrate)
{
    zsccflush (dp);

    baudrate &= CBAUD;
    if (baudrate == 0)
      return 1;
    
    /*
     * See the zscc manual for details.
     */

    zsccputreg(dp, zWR4, zWR4_1STOPBIT | zWR4_CLK);
    zsccputreg(dp, zWR10, zWR10_NRZ);
    
    zsccputreg(dp, zWR14, zWR14_NOP); /* stop BRG */
    zsccputreg(dp, zWR11, zWR11_TRXCOUT| zWR11_TRXCBRG| zWR11_TCLKBRG | zWR11_RCLKBRG);
#if 0
    zsccputreg(dp, zWR12,  zsccbrtc [baudrate] & 0xff);
    zsccputreg(dp, zWR13,  (zsccbrtc [baudrate] >> 8) & 0xff);
#endif
 
    zsccputreg(dp, zWR14, zWR14_BRGENABLE | zWR14_BRGSRC );
    
    zsccputreg(dp, zWR3, zWR3_RXENABLE | zWR3_RX8BITCHAR);
    zsccputreg(dp, zWR5, zWR5_TXENABLE| zWR5_RTS | zWR5_TX8BITCHAR | zWR5_DTR);
    return 0;
}


pzscc (int op, char *dat, int chan, int data)
{
    volatile zsccdp dp = (zsccdp) dat;

    switch (op) {
    case OP_INIT:
	return zsccinit (dp);
    case OP_BAUD:
	return zsccprogram (dp, data);
    case OP_TXRDY:
	return (dp->ucmd & zRR0_TXEMPTY);
    case OP_TX:
	dp->udata = data; wbflush ();
	break;
    case OP_RXRDY:
	return (dp->ucmd & zRR0_RXAVAIL);
    case OP_RX:
	return (dp->udata ); 
    case OP_FLUSH:
	zsccflush (dp);
	break;
    case OP_RXSTOP:
	/* rx flow control */
	zsccputreg (dp, zWR5, zWR5_TXENABLE| zWR5_TX8BITCHAR | zWR5_DTR | 
		    (data ? 0 : zWR5_RTS));
	break;
    }
    return 0;
}