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/* idp-inbyte.c --

 * Copyright (c) 1995 Cygnus Support

 *

 * The authors hereby grant permission to use, copy, modify, distribute,

 * and license this software and its documentation for any purpose, provided

 * that existing copyright notices are retained in all copies and that this

 * notice is included verbatim in any distributions. No written agreement,

 * license, or royalty fee is required for any of the authorized uses.

 * Modifications to this software may be copyrighted by their authors

 * and need not follow the licensing terms described here, provided that

 * the new terms are clearly indicated on the first page of each file where

 * they apply.

 */

#include <_ansi.h>

#include "mc68681reg.h"

/*

 * The DUART is mapped into the IDP address space in an unusual

 * manner.  The mc68681 is an 8 bit device located on the least

 * significant byte (byte0) of the data bus.  Bytes 3, 2, and

 * one have nothing in them and writes to these locations are

 * not valid.

 */

#define DUART_ADDR      0x00B00000

#define READREG(x)      (*((volatile char *) DUART_ADDR + (x * 4) + 3))

#define WRITEREG(x, y)  (*((char *) DUART_ADDR + (x * 4) + 3) = y)

/*

 * inbyte -- get a byte from the DUART RX buffer. This only reads

 *           from channel A

 */

char

_DEFUN_VOID (inbyte)

{

  while ((READREG (DUART_SRA) & 0x01) == 0x00)

    ;

  return (READREG (DUART_RBA));         /* read the byte */

}