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rs232.c
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rs232.c
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/*
* GZX - George's ZX Spectrum Emulator
* ZX Spectrum 128K RS-232 port emulation
*
* Copyright (c) 1999-2017 Jiri Svoboda
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* - The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <stdio.h>
#include "rs232.h"
void rs232_init(rs232_t *rs, uint32_t d_clocks)
{
rs->d_clocks = d_clocks;
rs->state = rs232_idle;
}
void rs232_write(rs232_t *rs, uint8_t val)
{
uint8_t b;
/* Spectrum ROM transmits MIDI data via CTS line */
b = (val >> rs232_cts) & 0x1;
if (rs->state == rs232_idle && (b == 0x0)) {
rs->state = rs232_sending;
rs->bit_no = 0;
rs->buf = 0x0;
} else if (rs->state == rs232_sending) {
rs->buf = (rs->buf >> 1) | (b << 7);
if (++rs->bit_no >= 8) {
rs->state = rs232_idle;
if (rs->sendchar != NULL)
rs->sendchar(rs->sendchar_arg, rs->buf);
}
}
}