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457 lines
16 KiB
C++
457 lines
16 KiB
C++
//
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// 6560.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 05/06/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#include "6560.hpp"
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using namespace MOS;
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MOS6560::MOS6560() :
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_crt(new Outputs::CRT::CRT(65*4, 4, Outputs::CRT::NTSC60, 1)),
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_horizontal_counter(0),
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_vertical_counter(0),
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_cycles_since_speaker_update(0),
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_is_odd_frame(false)
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{
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_crt->set_composite_sampling_function(
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"float composite_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)"
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"{"
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"uint c = texture(texID, coordinate).r;"
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"float y = float(c >> 4) / 4.0;"
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"uint yC = c & 15u;"
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"float phaseOffset = 6.283185308 * float(yC) / 16.0;"
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"float chroma = cos(phase + phaseOffset);"
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"return mix(y, step(yC, 14) * chroma, amplitude);"
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"}");
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// set up colours table
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// 0
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// 2, 6, 9, B,
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// 4, 5, 8, A, C, E
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// 3, 7, D, F
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// 1
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uint8_t luminances[16] = { // range is 0–4
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0, 4, 1, 3, 2, 2, 1, 3,
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2, 1, 2, 1, 2, 3, 2, 3
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};
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// uint8_t pal_chrominances[16] = { // range is 0–15; 15 is a special case meaning "no chrominance"
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// 15, 15, 5, 13, 2, 10, 0, 8,
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// 6, 7, 5, 13, 2, 10, 0, 8,
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// };
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uint8_t ntsc_chrominances[16] = {
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15, 15, 2, 10, 4, 12, 6, 14,
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0, 8, 2, 10, 4, 12, 6, 14,
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};
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for(int c = 0; c < 16; c++)
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{
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_colours[c] = (uint8_t)((luminances[c] << 4) | ntsc_chrominances[c]);
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}
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// show only the centre
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_crt->set_visible_area(_crt->get_rect_for_area(16, 237, 11*4, 55*4, 4.0f / 3.0f));
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_speaker.set_input_rate(255681.75); // assuming NTSC; clock rate / 4
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}
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void MOS6560::set_register(int address, uint8_t value)
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{
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address &= 0xf;
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_registers[address] = value;
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switch(address)
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{
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case 0x0:
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_interlaced = !!(value&0x80);
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_first_column_location = value & 0x7f;
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break;
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case 0x1:
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_first_row_location = value;
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break;
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case 0x2:
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_number_of_columns = value & 0x7f;
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_video_matrix_start_address = (uint16_t)((_video_matrix_start_address & 0x3c00) | ((value & 0x80) << 2));
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break;
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case 0x3:
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_number_of_rows = (value >> 1)&0x3f;
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_tall_characters = !!(value&0x01);
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break;
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case 0x5:
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_character_cell_start_address = (uint16_t)((value & 0x0f) << 10);
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_video_matrix_start_address = (uint16_t)((_video_matrix_start_address & 0x0200) | ((value & 0xf0) << 6));
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break;
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case 0xa:
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case 0xb:
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case 0xc:
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case 0xd:
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update_audio();
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_speaker.set_control(address - 0xa, value);
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break;
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case 0xe:
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update_audio();
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_auxiliary_colour = _colours[value >> 4];
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_speaker.set_volume(value & 0xf);
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break;
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case 0xf:
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if(_this_state == State::Border)
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{
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output_border(_cycles_in_state * 4);
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_cycles_in_state = 0;
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}
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_invertedCells = !((value >> 3)&1);
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_borderColour = _colours[value & 0x07];
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_backgroundColour = _colours[value >> 4];
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break;
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// TODO: audio, primarily
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default:
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break;
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}
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}
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uint8_t MOS6560::get_register(int address)
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{
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address &= 0xf;
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switch(address)
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{
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default: return _registers[address];
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case 0x03: return (uint8_t)(_vertical_counter << 7) | (_registers[3] & 0x7f);
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case 0x04: return (_vertical_counter >> 1) & 0xff;
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}
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}
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void MOS6560::output_border(unsigned int number_of_cycles)
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{
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uint8_t *colour_pointer = _crt->allocate_write_area(1);
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if(colour_pointer) *colour_pointer = _borderColour;
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_crt->output_level(number_of_cycles);
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}
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uint16_t MOS6560::get_address()
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{
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// keep track of the amount of time since the speaker was updated; lazy updates are applied
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_cycles_since_speaker_update++;
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// keep track of internal time relative to this scanline
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_horizontal_counter++;
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// check for end of scanline
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if(_horizontal_counter == 65)
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{
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_horizontal_counter = 0;
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_vertical_counter++;
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_column_counter = -1;
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if(_vertical_counter == (_interlaced ? (_is_odd_frame ? 262 : 263) : 261))
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{
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_is_odd_frame ^= true;
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_vertical_counter = 0;
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_row_counter = -1;
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}
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if(_row_counter >= 0)
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{
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_row_counter++;
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if(_row_counter == _number_of_rows*(_tall_characters ? 16 : 8)) _row_counter = -1;
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}
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else if(_vertical_counter == _first_row_location * 2)
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{
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_video_matrix_line_address_counter = _video_matrix_start_address;
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_row_counter = 0;
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}
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}
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if(_column_counter >= 0)
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{
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_column_counter++;
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if(_column_counter == _number_of_columns*2)
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{
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_column_counter = -1;
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if((_row_counter&(_tall_characters ? 15 : 7)) == (_tall_characters ? 15 : 7))
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{
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_video_matrix_line_address_counter = _video_matrix_address_counter;
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}
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}
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}
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else if(_horizontal_counter == _first_column_location)
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{
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_column_counter = 0;
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_video_matrix_address_counter = _video_matrix_line_address_counter;
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}
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// determine output state; colour burst and sync timing are currently a guess
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if(_horizontal_counter > 61) _this_state = State::ColourBurst;
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else if(_horizontal_counter > 57) _this_state = State::Sync;
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else
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{
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_this_state = (_column_counter >= 0 && _row_counter >= 0) ? State::Pixels : State::Border;
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}
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// apply vertical sync
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if(
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(_vertical_counter < 3 && (_is_odd_frame || !_interlaced)) ||
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(_interlaced &&
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(
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(_vertical_counter == 0 && _horizontal_counter > 32) ||
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(_vertical_counter == 1) || (_vertical_counter == 2) ||
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(_vertical_counter == 3 && _horizontal_counter <= 32)
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)
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))
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_this_state = State::Sync;
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// update the CRT
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if(_this_state != _output_state)
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{
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switch(_output_state)
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{
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case State::Sync: _crt->output_sync(_cycles_in_state * 4); break;
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case State::ColourBurst: _crt->output_colour_burst(_cycles_in_state * 4, _is_odd_frame ? 128 : 0, 0); break;
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case State::Border: output_border(_cycles_in_state * 4); break;
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case State::Pixels: _crt->output_data(_cycles_in_state * 4, 1); break;
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}
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_output_state = _this_state;
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_cycles_in_state = 0;
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pixel_pointer = nullptr;
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if(_output_state == State::Pixels)
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{
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pixel_pointer = _crt->allocate_write_area(260);
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}
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}
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_cycles_in_state++;
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// compute the address
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if(_this_state == State::Pixels)
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{
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/*
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Per http://tinyvga.com/6561 :
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The basic video timing is very simple. For
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every character the VIC-I is about to display, it first fetches the
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character code and colour, then the character appearance (from the
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character generator memory). The character codes are read on every
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raster line, thus making every line a "bad line". When the raster
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beam is outside of the text window, the videochip reads from $001c for
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most time. (Some videochips read from $181c instead.) The address
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occasionally varies, but it might also be due to a flaky bus. (By
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reading from unconnected address space, such as $9100-$910f, you can
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read the data fetched by the videochip on the previous clock cycle.)
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*/
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if(_column_counter&1)
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{
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return _character_cell_start_address + (_character_code*(_tall_characters ? 16 : 8)) + (_row_counter&(_tall_characters ? 15 : 7));
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}
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else
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{
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uint16_t result = _video_matrix_address_counter;
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_video_matrix_address_counter++;
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return result;
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}
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}
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return 0x1c;
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}
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void MOS6560::set_graphics_value(uint8_t value, uint8_t colour_value)
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{
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// TODO: this isn't correct, as _character_value will be
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// accessed second, then output will roll over. Probably it's
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// correct (given the delays upstream) to output all 8 on an &1
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// and to adjust the signalling to the CRT above?
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if(_this_state == State::Pixels)
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{
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if(_column_counter&1)
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{
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_character_value = value;
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if(pixel_pointer)
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{
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uint8_t cell_colour = _colours[_character_colour & 0x7];
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if(!(_character_colour&0x8))
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{
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uint8_t colours[2];
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if(_invertedCells)
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{
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colours[0] = cell_colour;
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colours[1] = _backgroundColour;
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}
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else
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{
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colours[0] = _backgroundColour;
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colours[1] = cell_colour;
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}
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pixel_pointer[0] = colours[(_character_value >> 7)&1];
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pixel_pointer[1] = colours[(_character_value >> 6)&1];
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pixel_pointer[2] = colours[(_character_value >> 5)&1];
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pixel_pointer[3] = colours[(_character_value >> 4)&1];
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pixel_pointer[4] = colours[(_character_value >> 3)&1];
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pixel_pointer[5] = colours[(_character_value >> 2)&1];
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pixel_pointer[6] = colours[(_character_value >> 1)&1];
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pixel_pointer[7] = colours[(_character_value >> 0)&1];
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}
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else
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{
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uint8_t colours[4] = {_backgroundColour, _borderColour, cell_colour, _auxiliary_colour};
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pixel_pointer[0] =
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pixel_pointer[1] = colours[(_character_value >> 6)&3];
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pixel_pointer[2] =
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pixel_pointer[3] = colours[(_character_value >> 4)&3];
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pixel_pointer[4] =
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pixel_pointer[5] = colours[(_character_value >> 2)&3];
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pixel_pointer[6] =
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pixel_pointer[7] = colours[(_character_value >> 0)&3];
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}
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pixel_pointer += 8;
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}
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}
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else
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{
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_character_code = value;
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_character_colour = colour_value;
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}
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}
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}
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void MOS6560::update_audio()
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{
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_speaker.run_for_cycles(_cycles_since_speaker_update >> 2);
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_cycles_since_speaker_update &= 3;
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}
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#pragma mark - Audio
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MOS6560::Speaker::Speaker() :
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_volume(0),
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_control_registers{0, 0, 0, 0},
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_shift_registers{0, 0, 0, 0},
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_counters{2, 1, 0, 0} // create a slight phase offset for the three channels
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{}
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void MOS6560::Speaker::set_volume(uint8_t volume)
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{
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_volume = volume;
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}
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void MOS6560::Speaker::set_control(int channel, uint8_t value)
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{
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_control_registers[channel] = value;
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}
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// Source: VICE. Not original.
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static uint8_t noise_pattern[] = {
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0x07, 0x1e, 0x1e, 0x1c, 0x1c, 0x3e, 0x3c, 0x38, 0x78, 0xf8, 0x7c, 0x1e, 0x1f, 0x8f, 0x07, 0x07,
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0xc1, 0xc0, 0xe0, 0xf1, 0xe0, 0xf0, 0xe3, 0xe1, 0xc0, 0xe0, 0x78, 0x7e, 0x3c, 0x38, 0xe0, 0xe1,
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0xc3, 0xc3, 0x87, 0xc7, 0x07, 0x1e, 0x1c, 0x1f, 0x0e, 0x0e, 0x1e, 0x0e, 0x0f, 0x0f, 0xc3, 0xc3,
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0xf1, 0xe1, 0xe3, 0xc1, 0xe3, 0xc3, 0xc3, 0xfc, 0x3c, 0x1e, 0x0f, 0x83, 0xc3, 0xc1, 0xc1, 0xc3,
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0xc3, 0xc7, 0x87, 0x87, 0xc7, 0x0f, 0x0e, 0x3c, 0x7c, 0x78, 0x3c, 0x3c, 0x3c, 0x38, 0x3e, 0x1c,
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0x7c, 0x1e, 0x3c, 0x0f, 0x0e, 0x3e, 0x78, 0xf0, 0xf0, 0xe0, 0xe1, 0xf1, 0xc1, 0xc3, 0xc7, 0xc3,
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0xe1, 0xf1, 0xe0, 0xe1, 0xf0, 0xf1, 0xe3, 0xc0, 0xf0, 0xe0, 0xf8, 0x70, 0xe3, 0x87, 0x87, 0xc0,
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0xf0, 0xe0, 0xf1, 0xe1, 0xe1, 0xc7, 0x83, 0x87, 0x83, 0x8f, 0x87, 0x87, 0xc7, 0x83, 0xc3, 0x83,
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0xc3, 0xf1, 0xe1, 0xc3, 0xc7, 0x81, 0xcf, 0x87, 0x03, 0x87, 0xc7, 0xc7, 0x87, 0x83, 0xe1, 0xc3,
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0x07, 0xc3, 0x87, 0x87, 0x07, 0x87, 0xc3, 0x87, 0x83, 0xe1, 0xc3, 0xc7, 0xc3, 0x87, 0x87, 0x8f,
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0x0f, 0x87, 0x87, 0x0f, 0xcf, 0x1f, 0x87, 0x8e, 0x0e, 0x07, 0x81, 0xc3, 0xe3, 0xc1, 0xe0, 0xf0,
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0xe0, 0xe3, 0x83, 0x87, 0x07, 0x87, 0x8e, 0x1e, 0x0f, 0x07, 0x87, 0x8f, 0x1f, 0x07, 0x87, 0xc1,
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0xf0, 0xe1, 0xe1, 0xe3, 0xc7, 0x0f, 0x03, 0x8f, 0x87, 0x0e, 0x1e, 0x1e, 0x0f, 0x87, 0x87, 0x0f,
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0x87, 0x1f, 0x0f, 0xc3, 0xc3, 0xf0, 0xf8, 0xf0, 0x70, 0xf1, 0xf0, 0xf0, 0xe1, 0xf0, 0xe0, 0x78,
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0x7c, 0x78, 0x7c, 0x70, 0x71, 0xe1, 0xe1, 0xc3, 0xc3, 0xc7, 0x87, 0x1c, 0x3c, 0x3c, 0x1c, 0x3c,
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0x7c, 0x1e, 0x1e, 0x1e, 0x1c, 0x3c, 0x78, 0xf8, 0xf8, 0xe1, 0xc3, 0x87, 0x1e, 0x1e, 0x3c, 0x3e,
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0x0f, 0x0f, 0x87, 0x1f, 0x8e, 0x0f, 0x0f, 0x8e, 0x1e, 0x1e, 0x1e, 0x1e, 0x0f, 0x0f, 0x8f, 0x87,
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0x87, 0xc3, 0x83, 0xc1, 0xe1, 0xc3, 0xc1, 0xc3, 0xc7, 0x8f, 0x0f, 0x0f, 0x0f, 0x0f, 0x83, 0xc7,
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0xc3, 0xc1, 0xe1, 0xe0, 0xf8, 0x3e, 0x3c, 0x3c, 0x3c, 0x3c, 0x3c, 0x78, 0x3e, 0x1e, 0x1e, 0x1e,
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0x0f, 0x0f, 0x0f, 0x1e, 0x0e, 0x1e, 0x1e, 0x0f, 0x0f, 0x87, 0x1f, 0x87, 0x87, 0x1c, 0x3e, 0x1f,
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0x0f, 0x0f, 0x8e, 0x3e, 0x0e, 0x3e, 0x1e, 0x1c, 0x3c, 0x7c, 0xfc, 0x38, 0x78, 0x78, 0x38, 0x78,
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0x70, 0xf8, 0x7c, 0x1e, 0x3c, 0x3c, 0x30, 0xf1, 0xf0, 0x70, 0x70, 0xe0, 0xf8, 0xf0, 0xf8, 0x78,
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0x78, 0x71, 0xe1, 0xf0, 0xe3, 0xc1, 0xf0, 0x71, 0xe3, 0xc7, 0x87, 0x8e, 0x3e, 0x0e, 0x1e, 0x3e,
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0x0f, 0x07, 0x87, 0x0c, 0x3e, 0x0f, 0x87, 0x0f, 0x1e, 0x3c, 0x3c, 0x38, 0x78, 0xf1, 0xe7, 0xc3,
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0xc3, 0xc7, 0x8e, 0x3c, 0x38, 0xf0, 0xe0, 0x7e, 0x1e, 0x3e, 0x0e, 0x0f, 0x0f, 0x0f, 0x03, 0xc3,
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0xc3, 0xc7, 0x87, 0x1f, 0x0e, 0x1e, 0x1c, 0x3c, 0x3c, 0x0f, 0x07, 0x07, 0xc7, 0xc7, 0x87, 0x87,
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0x8f, 0x0f, 0xc0, 0xf0, 0xf8, 0x60, 0xf0, 0xf0, 0xe1, 0xe3, 0xe3, 0xc3, 0xc3, 0xc3, 0x87, 0x0f,
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0x87, 0x8e, 0x1e, 0x1e, 0x3f, 0x1e, 0x0e, 0x1c, 0x3c, 0x7e, 0x1e, 0x3c, 0x38, 0x78, 0x78, 0x78,
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0x38, 0x78, 0x3c, 0xe1, 0xe3, 0x8f, 0x1f, 0x1c, 0x78, 0x70, 0x7e, 0x0f, 0x87, 0x07, 0xc3, 0xc7,
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0x0f, 0x1e, 0x3c, 0x0e, 0x0f, 0x0e, 0x1e, 0x03, 0xf0, 0xf0, 0xf1, 0xe3, 0xc1, 0xc7, 0xc0, 0xe1,
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0xe1, 0xe1, 0xe1, 0xe0, 0x70, 0xe1, 0xf0, 0x78, 0x70, 0xe3, 0xc7, 0x0f, 0xc1, 0xe1, 0xe3, 0xc3,
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0xc0, 0xf0, 0xfc, 0x1c, 0x3c, 0x70, 0xf8, 0x70, 0xf8, 0x78, 0x3c, 0x70, 0xf0, 0x78, 0x70, 0x7c,
|
||
0x7c, 0x3c, 0x38, 0x1e, 0x3e, 0x3c, 0x7e, 0x07, 0x83, 0xc7, 0xc1, 0xc1, 0xe1, 0xc3, 0xc3, 0xc3,
|
||
0xe1, 0xe1, 0xf0, 0x78, 0x7c, 0x3e, 0x0f, 0x1f, 0x07, 0x8f, 0x0f, 0x83, 0x87, 0xc1, 0xe3, 0xe3,
|
||
0xc3, 0xc3, 0xe1, 0xf0, 0xf8, 0xf0, 0x3c, 0x7c, 0x3c, 0x0f, 0x8e, 0x0e, 0x1f, 0x1f, 0x0e, 0x3c,
|
||
0x38, 0x78, 0x70, 0x70, 0xf0, 0xf0, 0xf8, 0x70, 0x70, 0x78, 0x38, 0x3c, 0x70, 0xe0, 0xf0, 0x78,
|
||
0xf1, 0xf0, 0x78, 0x3e, 0x3c, 0x0f, 0x07, 0x0e, 0x3e, 0x1e, 0x3f, 0x1e, 0x0e, 0x0f, 0x87, 0x87,
|
||
0x07, 0x0f, 0x07, 0xc7, 0x8f, 0x0f, 0x87, 0x1e, 0x1e, 0x1f, 0x1e, 0x1e, 0x3c, 0x1e, 0x1c, 0x3e,
|
||
0x0f, 0x03, 0xc3, 0x81, 0xe0, 0xf0, 0xfc, 0x38, 0x3c, 0x3e, 0x0e, 0x1e, 0x1c, 0x7c, 0x1e, 0x1f,
|
||
0x0e, 0x3e, 0x1c, 0x78, 0x78, 0x7c, 0x1e, 0x3e, 0x1e, 0x3c, 0x1f, 0x0f, 0x1f, 0x0f, 0x0f, 0x8f,
|
||
0x1c, 0x3c, 0x78, 0xf8, 0xf0, 0xf8, 0x70, 0xf0, 0x78, 0x78, 0x3c, 0x3c, 0x78, 0x3c, 0x1f, 0x0f,
|
||
0x07, 0x86, 0x1c, 0x1e, 0x1c, 0x1e, 0x1e, 0x1f, 0x03, 0xc3, 0xc7, 0x8e, 0x3c, 0x3c, 0x1c, 0x18,
|
||
0xf0, 0xe1, 0xc3, 0xe1, 0xc1, 0xe1, 0xe3, 0xc3, 0xc3, 0xe3, 0xc3, 0x83, 0x87, 0x83, 0x87, 0x0f,
|
||
0x07, 0x07, 0xe1, 0xe1, 0xe0, 0x7c, 0x78, 0x38, 0x78, 0x78, 0x3c, 0x1f, 0x0f, 0x8f, 0x0e, 0x07,
|
||
0x0f, 0x07, 0x83, 0xc3, 0xc3, 0x81, 0xf0, 0xf8, 0xf1, 0xe0, 0xe3, 0xc7, 0x1c, 0x3e, 0x1e, 0x0f,
|
||
0x0f, 0xc3, 0xf0, 0xf0, 0xe3, 0x83, 0xc3, 0xc7, 0x07, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x07, 0x87,
|
||
0x0f, 0x0f, 0x0e, 0x0f, 0x0f, 0x1e, 0x0f, 0x0f, 0x87, 0x87, 0x87, 0x8f, 0xc7, 0xc7, 0x83, 0x83,
|
||
0xc3, 0xc7, 0x8f, 0x87, 0x07, 0xc3, 0x8e, 0x1e, 0x38, 0x3e, 0x3c, 0x38, 0x7c, 0x1f, 0x1c, 0x38,
|
||
0x3c, 0x78, 0x7c, 0x1e, 0x1c, 0x3c, 0x3f, 0x1e, 0x0e, 0x3e, 0x1c, 0x3c, 0x1f, 0x0f, 0x07, 0xc3,
|
||
0xe3, 0x83, 0x87, 0x81, 0xc1, 0xe3, 0xcf, 0x0e, 0x0f, 0x1e, 0x3e, 0x1e, 0x1f, 0x0f, 0x8f, 0xc3,
|
||
0x87, 0x0e, 0x03, 0xf0, 0xf0, 0x70, 0xe0, 0xe1, 0xe1, 0xc7, 0x8e, 0x0f, 0x0f, 0x1e, 0x0e, 0x1e,
|
||
0x1f, 0x1c, 0x78, 0xf0, 0xf1, 0xf1, 0xe0, 0xf1, 0xe1, 0xe1, 0xe0, 0xe0, 0xf1, 0xc1, 0xf0, 0x71,
|
||
0xe1, 0xc3, 0x83, 0xc7, 0x83, 0xe1, 0xe1, 0xf8, 0x70, 0xf0, 0xf0, 0xf0, 0xf0, 0xf0, 0x70, 0xf8,
|
||
0x70, 0x70, 0x61, 0xe0, 0xf0, 0xe1, 0xe0, 0x78, 0x71, 0xe0, 0xf0, 0xf8, 0x38, 0x1e, 0x1c, 0x38,
|
||
0x70, 0xf8, 0x60, 0x78, 0x38, 0x3c, 0x3f, 0x1f, 0x0f, 0x1f, 0x0f, 0x1f, 0x87, 0x87, 0x83, 0x87,
|
||
0x83, 0xe1, 0xe1, 0xf0, 0x78, 0xf1, 0xf0, 0x70, 0x38, 0x38, 0x70, 0xe0, 0xe3, 0xc0, 0xe0, 0xf8,
|
||
0x78, 0x78, 0xf8, 0x38, 0xf1, 0xe1, 0xe1, 0xc3, 0x87, 0x87, 0x0e, 0x1e, 0x1f, 0x0e, 0x0e, 0x0f,
|
||
0x0f, 0x87, 0xc3, 0x87, 0x07, 0x83, 0xc0, 0xf0, 0x38, 0x3c, 0x3c, 0x38, 0xf0, 0xfc, 0x3e, 0x1e,
|
||
0x1c, 0x1c, 0x38, 0x70, 0xf0, 0xf1, 0xe0, 0xf0, 0xe0, 0xe0, 0xf1, 0xe3, 0xe0, 0xe1, 0xf0, 0xf0,
|
||
0x78, 0x7c, 0x78, 0x3c, 0x78, 0x78, 0x38, 0x78, 0x78, 0x78, 0x78, 0x70, 0xe3, 0x83, 0x83, 0xe0,
|
||
0xc3, 0xc1, 0xe1, 0xc1, 0xc1, 0xc1, 0xe3, 0xc3, 0xc7, 0x1e, 0x0e, 0x1f, 0x1e, 0x1e, 0x0f, 0x0f,
|
||
0x0e, 0x0e, 0x0e, 0x07, 0x83, 0x87, 0x87, 0x0e, 0x07, 0x8f, 0x0f, 0x0f, 0x0f, 0x0e, 0x1c, 0x70,
|
||
0xe1, 0xe0, 0x71, 0xc1, 0x83, 0x83, 0x87, 0x0f, 0x1e, 0x18, 0x78, 0x78, 0x7c, 0x3e, 0x1c, 0x38,
|
||
0xf0, 0xe1, 0xe0, 0x78, 0x70, 0x38, 0x3c, 0x3e, 0x1e, 0x3c, 0x1e, 0x1c, 0x70, 0x3c, 0x38, 0x3f,
|
||
};
|
||
|
||
#define shift(r) _shift_registers[r] = (_shift_registers[r] << 1) | (((_shift_registers[r]^0x80)&_control_registers[r]) >> 7);
|
||
#define increment(r) _shift_registers[r] = (_shift_registers[r]+1)%8191;
|
||
#define update(r, m, up) _counters[r]++; if((_counters[r] >> m) == 0x7f) { up(r); _counters[r] = _control_registers[r]&0x7f; }
|
||
|
||
void MOS6560::Speaker::get_samples(unsigned int number_of_samples, int16_t *target)
|
||
{
|
||
for(unsigned int c = 0; c < number_of_samples; c++)
|
||
{
|
||
update(0, 2, shift);
|
||
update(1, 1, shift);
|
||
update(2, 0, shift);
|
||
update(3, 1, increment);
|
||
|
||
// this sums the output of all three sounds channels plus a DC offset for volume;
|
||
// TODO: what's the real ratio of this stuff?
|
||
target[c] = (
|
||
(_shift_registers[0]&1) +
|
||
(_shift_registers[1]&1) +
|
||
(_shift_registers[2]&1) +
|
||
((noise_pattern[_shift_registers[3] >> 3] >> (_shift_registers[3]&7))&(_control_registers[3] >> 7)&1)
|
||
) * _volume * 700 + _volume * 44;
|
||
}
|
||
}
|
||
|
||
void MOS6560::Speaker::skip_samples(unsigned int number_of_samples)
|
||
{
|
||
for(unsigned int c = 0; c < number_of_samples; c++)
|
||
{
|
||
update(0, 2, shift);
|
||
update(1, 1, shift);
|
||
update(2, 0, shift);
|
||
update(3, 1, increment);
|
||
}
|
||
}
|
||
|
||
#undef shift
|
||
#undef increment
|
||
#undef update
|