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Diffstat (limited to 'src/lib/formats/sorc_cas.cpp')
-rw-r--r-- | src/lib/formats/sorc_cas.cpp | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/src/lib/formats/sorc_cas.cpp b/src/lib/formats/sorc_cas.cpp new file mode 100644 index 00000000000..6983dd0ba74 --- /dev/null +++ b/src/lib/formats/sorc_cas.cpp @@ -0,0 +1,158 @@ +// license:BSD-3-Clause +// copyright-holders:Robbbert +/******************************************************************** + +Support for Exidy Sorcerer cassette images + + +Sorcerer tapes consist of these sections: +1. A high tone whenever idle +2. A header +3. The data, in blocks of 256 bytes plus a CRC byte +4. The last block may be shorter, depending on the number of bytes + left to save. + +Each byte has 1 start bit, 8 data bits (0-7), 2 stop bits. + +The default speed is 1200 baud, which is what we emulate here. +A high bit is 1 cycle of 1200 Hz, while a low bit is half a cycle +of 600 Hz. + +Formats: +TAPE - this contains a byte for each real byte, including all the +header and leader bytes. + + +********************************************************************/ + +#include <assert.h> + +#include "sorc_cas.h" + +#define WAVEENTRY_LOW -32768 +#define WAVEENTRY_HIGH 32767 + +#define SORCERER_WAV_FREQUENCY 4800 + +// image size +static int sorcerer_image_size; +static bool level; + +static int sorcerer_put_samples(INT16 *buffer, int sample_pos, int count) +{ + if (buffer) + { + for (int i=0; i<count; i++) + buffer[sample_pos + i] = level ? WAVEENTRY_LOW : WAVEENTRY_HIGH; + + level ^= 1; + } + + return count; +} + +static int sorcerer_output_bit(INT16 *buffer, int sample_pos, bool bit) +{ + int samples = 0; + + if (bit) + { + samples += sorcerer_put_samples(buffer, sample_pos + samples, 2); + samples += sorcerer_put_samples(buffer, sample_pos + samples, 2); + } + else + { + samples += sorcerer_put_samples(buffer, sample_pos + samples, 4); + } + + return samples; +} + +static int sorcerer_output_byte(INT16 *buffer, int sample_pos, UINT8 byte) +{ + int samples = 0; + UINT8 i; + + /* start */ + samples += sorcerer_output_bit (buffer, sample_pos + samples, 0); + + /* data */ + for (i = 0; i<8; i++) + samples += sorcerer_output_bit (buffer, sample_pos + samples, (byte >> i) & 1); + + /* stop */ + for (i = 0; i<2; i++) + samples += sorcerer_output_bit (buffer, sample_pos + samples, 1); + + return samples; +} + +static int sorcerer_handle_cassette(INT16 *buffer, const UINT8 *bytes) +{ + UINT32 sample_count = 0; + UINT32 i; + + /* idle */ + for (i=0; i<2000; i++) + sample_count += sorcerer_output_bit(buffer, sample_count, 1); + + /* data */ + for (i=0; i<sorcerer_image_size; i++) + sample_count += sorcerer_output_byte(buffer, sample_count, bytes[i]); + + return sample_count; +} + + +/******************************************************************* + Generate samples for the tape image +********************************************************************/ + +static int sorcerer_cassette_fill_wave(INT16 *buffer, int length, UINT8 *bytes) +{ + return sorcerer_handle_cassette(buffer, bytes); +} + +/******************************************************************* + Calculate the number of samples needed for this tape image +********************************************************************/ + +static int sorcerer_cassette_calculate_size_in_samples(const UINT8 *bytes, int length) +{ + sorcerer_image_size = length; + + return sorcerer_handle_cassette(NULL, bytes); +} + +static const struct CassetteLegacyWaveFiller sorcerer_legacy_fill_wave = +{ + sorcerer_cassette_fill_wave, /* fill_wave */ + -1, /* chunk_size */ + 0, /* chunk_samples */ + sorcerer_cassette_calculate_size_in_samples, /* chunk_sample_calc */ + SORCERER_WAV_FREQUENCY, /* sample_frequency */ + 0, /* header_samples */ + 0 /* trailer_samples */ +}; + +static casserr_t sorcerer_cassette_identify(cassette_image *cassette, struct CassetteOptions *opts) +{ + return cassette_legacy_identify(cassette, opts, &sorcerer_legacy_fill_wave); +} + +static casserr_t sorcerer_cassette_load(cassette_image *cassette) +{ + return cassette_legacy_construct(cassette, &sorcerer_legacy_fill_wave); +} + +static const struct CassetteFormat sorcerer_cassette_image_format = +{ + "tape", + sorcerer_cassette_identify, + sorcerer_cassette_load, + NULL +}; + +CASSETTE_FORMATLIST_START(sorcerer_cassette_formats) + CASSETTE_FORMAT(sorcerer_cassette_image_format) +CASSETTE_FORMATLIST_END |