source: trunk/libs/newlib/src/libgloss/m68k/idp-inbyte.c @ 546

Last change on this file since 546 was 444, checked in by satin@…, 6 years ago

add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc

File size: 1.4 KB
Line 
1/* idp-inbyte.c --
2 * Copyright (c) 1995 Cygnus Support
3 *
4 * The authors hereby grant permission to use, copy, modify, distribute,
5 * and license this software and its documentation for any purpose, provided
6 * that existing copyright notices are retained in all copies and that this
7 * notice is included verbatim in any distributions. No written agreement,
8 * license, or royalty fee is required for any of the authorized uses.
9 * Modifications to this software may be copyrighted by their authors
10 * and need not follow the licensing terms described here, provided that
11 * the new terms are clearly indicated on the first page of each file where
12 * they apply.
13 */
14
15#include <_ansi.h>
16#include "mc68681reg.h"
17
18/*
19 * The DUART is mapped into the IDP address space in an unusual
20 * manner.  The mc68681 is an 8 bit device located on the least
21 * significant byte (byte0) of the data bus.  Bytes 3, 2, and
22 * one have nothing in them and writes to these locations are
23 * not valid.
24 */
25
26#define DUART_ADDR      0x00B00000
27#define READREG(x)      (*((volatile char *) DUART_ADDR + (x * 4) + 3))
28#define WRITEREG(x, y)  (*((char *) DUART_ADDR + (x * 4) + 3) = y)
29
30/*
31 * inbyte -- get a byte from the DUART RX buffer. This only reads
32 *           from channel A
33 */
34char
35inbyte (void)
36{
37  while ((READREG (DUART_SRA) & 0x01) == 0x00)
38    ;
39
40  return (READREG (DUART_RBA));         /* read the byte */
41}
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