mirror of
https://github.com/holub/mame
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380 lines
9.4 KiB
C
380 lines
9.4 KiB
C
// license:BSD-3-Clause
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// copyright-holders:Robbbert
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/********************************************************************
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Support for SOL-20 cassette images
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SOL20 tapes consist of these sections:
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1. A high tone whenever idle
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2. A header
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3. The data, in blocks of 256 bytes plus a CRC byte
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4. The last block may be shorter, depending on the number of bytes
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left to save.
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Each byte has 1 start bit, 8 data bits (0-7), 2 stop bits.
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The default speed is 1200 baud, which is what we emulate here.
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A high bit is 1 cycle of 1200 Hz, while a low bit is half a cycle
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of 600 Hz.
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Formats:
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SVT - The full explanation may be found on the Solace web site,
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however this is a summary of what we support.
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C (carrier) time in decaseconds
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D (data bytes) in ascii text
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H (header) tape header info
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Multiple programs
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Unsupported:
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B (set baud rate) B 300 or B 1200
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F load ENT file
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S (silence) time in decaseconds
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bad-byte symbols
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escaped characters
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********************************************************************/
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#include <assert.h>
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#include "sol_cas.h"
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#define WAVEENTRY_LOW -32768
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#define WAVEENTRY_HIGH 32767
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#define SOL20_WAV_FREQUENCY 4800
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// image size
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static UINT32 sol20_image_size;
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static bool level;
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static UINT8 sol20_cksm_byte;
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static UINT32 sol20_byte_num;
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static UINT8 sol20_header[16];
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static int sol20_put_samples(INT16 *buffer, int sample_pos, int count)
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{
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if (buffer)
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{
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for (int i=0; i<count; i++)
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buffer[sample_pos + i] = level ? WAVEENTRY_LOW : WAVEENTRY_HIGH;
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level ^= 1;
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}
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return count;
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}
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static int sol20_output_bit(INT16 *buffer, int sample_pos, bool bit)
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{
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int samples = 0;
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if (bit)
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{
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samples += sol20_put_samples(buffer, sample_pos + samples, 2);
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samples += sol20_put_samples(buffer, sample_pos + samples, 2);
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}
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else
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{
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samples += sol20_put_samples(buffer, sample_pos + samples, 4);
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}
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return samples;
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}
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static int sol20_output_byte(INT16 *buffer, int sample_pos, UINT8 byte)
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{
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int samples = 0;
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UINT8 i;
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/* start */
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samples += sol20_output_bit (buffer, sample_pos + samples, 0);
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/* data */
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for (i = 0; i<8; i++)
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samples += sol20_output_bit (buffer, sample_pos + samples, (byte >> i) & 1);
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/* stop */
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for (i = 0; i<2; i++)
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samples += sol20_output_bit (buffer, sample_pos + samples, 1);
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return samples;
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}
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// Calculate checksum
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static UINT8 sol20_calc_cksm(UINT8 cksm, UINT8 data)
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{
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data -= cksm;
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cksm = data;
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data ^= cksm;
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data ^= 0xff;
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data -= cksm;
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return data;
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}
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// Ignore remainder of line
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static void sol20_scan_to_eol(const UINT8 *bytes)
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{
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bool t = 1;
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while (t)
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{
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if (sol20_byte_num >= sol20_image_size)
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{
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sol20_byte_num = 0;
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t = 0;
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}
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else
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if (bytes[sol20_byte_num] == 0x0d)
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t = 0;
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else
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sol20_byte_num++;
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}
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}
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// skip spaces and symbols looking for a hex digit
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static void sol20_scan_to_hex(const UINT8 *bytes)
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{
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bool t = 1;
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while (t)
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{
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if (sol20_byte_num >= sol20_image_size)
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{
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sol20_byte_num = 0;
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t = 0;
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}
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else
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{
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UINT8 chr = bytes[sol20_byte_num];
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if (chr == 0x0d)
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t = 0;
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else
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if (((chr >= '0') && (chr <= '9')) || ((chr >= 'A') && (chr <= 'F')))
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t = 0;
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else
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sol20_byte_num++;
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}
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}
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}
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// Turn n digits into hex
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static int sol20_read_hex(const UINT8 *bytes, UINT8 numdigits)
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{
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int data = 0;
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UINT8 i,chr;
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for (i = 0; i < numdigits; i++)
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{
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chr = bytes[sol20_byte_num];
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if ((chr >= '0') && (chr <= '9'))
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{
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data = (data << 4) | (chr-48);
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sol20_byte_num++;
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}
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else
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if ((chr >= 'A') && (chr <= 'F'))
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{
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data = (data << 4) | (chr-55);
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sol20_byte_num++;
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}
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else
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i = numdigits;
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}
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return data;
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}
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// Turn digits into decimal
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static int sol20_read_dec(const UINT8 *bytes)
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{
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int data = 0;
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while ((bytes[sol20_byte_num] >= '0') && (bytes[sol20_byte_num] <= '9'))
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{
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data = data*10 + bytes[sol20_byte_num] - 48;
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sol20_byte_num++;
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}
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return data;
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}
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static int sol20_handle_cassette(INT16 *buffer, const UINT8 *bytes)
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{
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UINT32 sample_count = 0;
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UINT32 i = 0,t = 0;
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UINT8 c = 0;
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sol20_byte_num = 1;
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bool process_d = 0;
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UINT16 length = 0;
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// 1st line of file must say SVT
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if ((bytes[0] == 'S') && (bytes[1] == 'V') && (bytes[2] == 'T'))
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{ }
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else
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return sample_count;
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// ignore remainder of line
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sol20_scan_to_eol(bytes);
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// process the commands
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while (sol20_byte_num)
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{
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sol20_byte_num+=2; // bump to start of next line
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UINT8 chr = bytes[sol20_byte_num]; // Get command
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if (sol20_byte_num >= sol20_image_size)
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sol20_byte_num = 0;
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else
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{
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switch (chr)
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{
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case 0x0d:
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break;
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case 'C': // carrier
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{
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if (c) // if this is the next file, clean up after the previous one
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{
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sample_count += sol20_output_byte(buffer, sample_count, sol20_cksm_byte); // final checksum if needed
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c = 0;
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}
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sol20_byte_num+=2; // bump to parameter
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t = sol20_read_dec(bytes) * 140; // convert 10th of seconds to number of ones
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for (i = 0; i < t; i++)
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sample_count += sol20_output_bit(buffer, sample_count, 1);
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sol20_scan_to_eol(bytes);
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break;
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}
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case 'H': // header
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{
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if (c) // if this is the next file, clean up after the previous one
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{
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sample_count += sol20_output_byte(buffer, sample_count, sol20_cksm_byte); // final checksum if needed
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c = 0;
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}
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sol20_byte_num+=2; // bump to file name
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sol20_header[0] = bytes[sol20_byte_num++];
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sol20_header[1] = bytes[sol20_byte_num++];
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sol20_header[2] = bytes[sol20_byte_num++];
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sol20_header[3] = bytes[sol20_byte_num++];
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sol20_header[4] = bytes[sol20_byte_num++];
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sol20_header[5] = 0;
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sol20_scan_to_hex(bytes); // bump to file type
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sol20_header[6] = sol20_read_hex(bytes, 2);
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sol20_scan_to_hex(bytes); // bump to length
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length = sol20_read_hex(bytes, 4);
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sol20_header[7] = length;
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sol20_header[8] = length >> 8;
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sol20_scan_to_hex(bytes); // bump to load-address
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i = sol20_read_hex(bytes, 4);
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sol20_header[9] = i;
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sol20_header[10] = i >> 8;
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sol20_scan_to_hex(bytes); // bump to exec-address
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i = sol20_read_hex(bytes, 4);
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sol20_header[11] = i;
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sol20_header[12] = i >> 8;
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sol20_header[13] = 0;
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sol20_header[14] = 0;
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sol20_header[15] = 0;
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sol20_cksm_byte = 0;
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for (i = 0; i < 16; i++)
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sol20_cksm_byte = sol20_calc_cksm(sol20_cksm_byte, sol20_header[i]);
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// write leader
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for (i = 0; i < 100; i++)
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sample_count += sol20_output_byte(buffer, sample_count, 0);
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// write SOH
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sample_count += sol20_output_byte(buffer, sample_count, 1);
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// write Header
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for (i = 0; i < 16; i++)
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sample_count += sol20_output_byte(buffer, sample_count, sol20_header[i]);
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// write checksum
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sample_count += sol20_output_byte(buffer, sample_count, sol20_cksm_byte);
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sol20_cksm_byte = 0;
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process_d = 1;
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sol20_scan_to_eol(bytes);
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break;
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}
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case 'D': // data
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{
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sol20_byte_num+=2; // bump to first byte
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while ((bytes[sol20_byte_num] != 0x0d) && sol20_byte_num && process_d)
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{
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t = sol20_read_hex(bytes, 2);
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sample_count += sol20_output_byte(buffer, sample_count, t);
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sol20_cksm_byte = sol20_calc_cksm(sol20_cksm_byte, t);
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c++;
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length--;
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if (!length)
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process_d = 0;
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if (!c)
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{
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sample_count += sol20_output_byte(buffer, sample_count, sol20_cksm_byte);
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sol20_cksm_byte = 0;
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}
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sol20_scan_to_hex(bytes);
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}
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}
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default: // everything else is ignored
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sol20_scan_to_eol(bytes);
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break;
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}
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}
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}
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if (c) // reached the end of the svt file
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sample_count += sol20_output_byte(buffer, sample_count, sol20_cksm_byte); // final checksum if needed
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return sample_count;
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}
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/*******************************************************************
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Generate samples for the tape image
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********************************************************************/
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static int sol20_cassette_fill_wave(INT16 *buffer, int length, UINT8 *bytes)
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{
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return sol20_handle_cassette(buffer, bytes);
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}
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/*******************************************************************
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Calculate the number of samples needed for this tape image
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********************************************************************/
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static int sol20_cassette_calculate_size_in_samples(const UINT8 *bytes, int length)
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{
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sol20_image_size = length;
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return sol20_handle_cassette(NULL, bytes);
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}
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static const struct CassetteLegacyWaveFiller sol20_legacy_fill_wave =
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{
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sol20_cassette_fill_wave, /* fill_wave */
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-1, /* chunk_size */
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0, /* chunk_samples */
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sol20_cassette_calculate_size_in_samples, /* chunk_sample_calc */
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SOL20_WAV_FREQUENCY, /* sample_frequency */
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0, /* header_samples */
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0 /* trailer_samples */
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};
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static casserr_t sol20_cassette_identify(cassette_image *cassette, struct CassetteOptions *opts)
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{
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return cassette_legacy_identify(cassette, opts, &sol20_legacy_fill_wave);
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}
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static casserr_t sol20_cassette_load(cassette_image *cassette)
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{
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return cassette_legacy_construct(cassette, &sol20_legacy_fill_wave);
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}
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static const struct CassetteFormat sol20_cassette_image_format =
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{
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"svt",
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sol20_cassette_identify,
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sol20_cassette_load,
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NULL
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};
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CASSETTE_FORMATLIST_START(sol20_cassette_formats)
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CASSETTE_FORMAT(sol20_cassette_image_format)
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CASSETTE_FORMATLIST_END
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