/*
 * Dual systems sio4
 *
 *	s4open()
 *	getchar()
 *	putchar()
 */

#define until(a) while(!(a))

#define IOADDR 0xff0000
#define SIOBASE (IOADDR + 0x20)

/*
 * rcon bits
 */

#define RENABLE (1 << 1)		/* receiver enable */
#define RDISABLE 0

/*
 * fifo status bits.
 */

#define FREADY (1 << 6)

/*
 * sstatus bits.
 */

#define INREADY (1 << 1)
#define OUTREADY (1 << 0)

struct sio
	{
	char
		addr0,		/* low byte dma address */
		addr1,		/* high byte dma address */
		addr2,		/* extended byte of dma address */

		rcon,		/* receiver control port */

		count0,		/* low byte of dma  count */
		count1,		/* high byte of dma count */

		enable,		/* start / stop enable */
		dmacon,		/* dma control and status */

		sdata,		/* uart data port */
		sstatus,	/* uart status port */
		smode,		/* uart mode register */
		scommand,	/* uart command register */

		fstatus,	/* fifo status */
		fdata,		/* fifo data */

		dmaglob,	/* global dma status */
		select;		/* tty select port */
	};

static struct sio *s4 = {0};

#define REG1 0x27
#define REG2 0x6e
#define REG3 0x7d

/*
 * initialize channel 0
 */

s4open ()
	{
	s4 = (struct sio *) SIOBASE;

	s4->select = 0;
	
	s4->scommand = REG1;
	s4->smode = REG2;
	s4->smode = REG3;

	s4->rcon = RDISABLE;
	}


/*
 * read a character in
 * low byte
 *
 * Status in high byte.
 */

getchar ()
	{
	until(s4->sstatus & INREADY)
		;

	return s4->sdata;
	}

/* 
 * Write character c to port p
 */

putchar (c)
	{
	s4->select = 0;

	until(s4->sstatus & OUTREADY)
		;

	s4->sdata = c;
	}