42 lines
1.4 KiB
C
42 lines
1.4 KiB
C
/* idp-inbyte.c --
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* Copyright (c) 1995 Cygnus Support
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*
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* The authors hereby grant permission to use, copy, modify, distribute,
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* and license this software and its documentation for any purpose, provided
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* that existing copyright notices are retained in all copies and that this
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* notice is included verbatim in any distributions. No written agreement,
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* license, or royalty fee is required for any of the authorized uses.
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* Modifications to this software may be copyrighted by their authors
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* and need not follow the licensing terms described here, provided that
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* the new terms are clearly indicated on the first page of each file where
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* they apply.
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*/
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#include <_ansi.h>
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#include "mc68681reg.h"
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/*
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* The DUART is mapped into the IDP address space in an unusual
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* manner. The mc68681 is an 8 bit device located on the least
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* significant byte (byte0) of the data bus. Bytes 3, 2, and
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* one have nothing in them and writes to these locations are
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* not valid.
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*/
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#define DUART_ADDR 0x00B00000
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#define READREG(x) (*((volatile char *) DUART_ADDR + (x * 4) + 3))
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#define WRITEREG(x, y) (*((char *) DUART_ADDR + (x * 4) + 3) = y)
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/*
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* inbyte -- get a byte from the DUART RX buffer. This only reads
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* from channel A
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*/
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char
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_DEFUN_VOID (inbyte)
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{
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while ((READREG (DUART_SRA) & 0x01) == 0x00)
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;
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return (READREG (DUART_RBA)); /* read the byte */
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}
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