toolchain/gcc/libgloss/m68k/idp-outbyte.c

   1 /* idp-outbyte.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  * raw_outbyte -- send a byte to the DUART buffer. This only sends
  32  *           to channel A.
  33  */
  34 static void
  35 _DEFUN (raw_outbyte, (byte),
  36         char byte)
  37 {
  38   /* First, wait for the UART to finish clocking out the last
  39      character we sent, if any.  Then, give it the next character to
  40      work on.  By waiting first, then handing off a new character, we
  41      allow the UART to work while the processor (perhaps) does other
  42      things; if we waited after sending each character, there'd be no
  43      opportunity for parallelism.  */
  44   while ((READREG (DUART_SRA) & 0x04) == 0x00)
  45     ;
  46
  47   WRITEREG (DUART_TBA, byte);           /* write the byte */
  48 }
  49
  50
  51 /*
  52  * outbyte -- send BYTE out the DUART's channel A, for display to
  53  *      the user.
  54  *
  55  *      Normally, this is identical to raw_outbyte, but if
  56  *      GDB_MONITOR_OUTPUT is #defined, we prefix each byte we send
  57  *      with a ^O character (ASCII 15).  This is a signal to GDB's
  58  *      `rom68k' target to pass the character directly on to the user;
  59  *      it allows programs to do console output under GDB.
  60  *
  61  *      We compile this file twice: once with GDB_MONITOR_OUTPUT
  62  *      #defined, and once without.  The former .o file we put in
  63  *      libidpgdb.a, which is included in the link by idpgdb.ld; the
  64  *      latter we put in libidp.a, which is selected by idp.ld.
  65  */
  66 void
  67 _DEFUN (outbyte, (byte),
  68         char byte)
  69 {
  70 #ifdef GDB_MONITOR_OUTPUT
  71   raw_outbyte (0x0f);
  72 #endif
  73   raw_outbyte (byte);
  74 }