CLK/Components/6560/6560.hpp

//
//  6560.hpp
//  Clock Signal
//
//  Created by Thomas Harte on 05/06/2016.
//  Copyright © 2016 Thomas Harte. All rights reserved.
//

#ifndef _560_hpp
#define _560_hpp

#include "../../Outputs/CRT/CRT.hpp"
#include "../../Outputs/Speaker.hpp"

namespace MOS {

// audio state
class Speaker: public ::Outputs::Filter<Speaker> {
	public:
		Speaker();

		void set_volume(uint8_t volume);
		void set_control(int channel, uint8_t value);

		void get_samples(unsigned int number_of_samples, int16_t *target);
		void skip_samples(unsigned int number_of_samples);

	private:
		unsigned int counters_[4];
		unsigned int shift_registers_[4];
		uint8_t control_registers_[4];
		uint8_t volume_;
};

/*!
	The 6560 Video Interface Chip ('VIC') is a video and audio output chip; it therefore vends both a @c CRT and a @c Speaker.

	To run the VIC for a cycle, the caller should call @c get_address, make the requested bus access
	and call @c set_graphics_value with the result.

	@c set_register and @c get_register provide register access.
*/
template <class T> class MOS6560 {
	public:
		MOS6560() :
			crt_(new Outputs::CRT::CRT(65*4, 4, Outputs::CRT::NTSC60, 1)),
			speaker_(new Speaker),
			horizontal_counter_(0),
			vertical_counter_(0),
			cycles_since_speaker_update_(0),
			is_odd_frame_(false),
			is_odd_line_(false)
		{
			crt_->set_composite_sampling_function(
				"float composite_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)"
				"{"
					"uint c = texture(texID, coordinate).r;"
					"float y = float(c >> 4) / 4.0;"
					"uint yC = c & 15u;"
					"float phaseOffset = 6.283185308 * float(yC) / 16.0;"

					"float chroma = cos(phase + phaseOffset);"
					"return mix(y, step(yC, 14) * chroma, amplitude);"
				"}");

			// default to NTSC
			set_output_mode(OutputMode::NTSC);
		}

		void set_clock_rate(double clock_rate)
		{
			speaker_->set_input_rate((float)(clock_rate / 4.0));
		}

		std::shared_ptr<Outputs::CRT::CRT> get_crt() { return crt_; }
		std::shared_ptr<Outputs::Speaker> get_speaker() { return speaker_; }

		enum OutputMode {
			PAL, NTSC
		};

		/*!
			Sets the output mode to either PAL or NTSC.
		*/
		void set_output_mode(OutputMode output_mode)
		{
			output_mode_ = output_mode;
			uint8_t luminances[16] = {		// range is 0–4
				0, 4, 1, 3, 2, 2, 1, 3,
				2, 1, 2, 1, 2, 3, 2, 3
			};
			uint8_t pal_chrominances[16] = {	// range is 0–15; 15 is a special case meaning "no chrominance"
				15, 15, 5, 13, 2, 10, 0, 8,
				6, 7, 5, 13, 2, 10, 0, 8,
			};
			uint8_t ntsc_chrominances[16] = {
				15, 15, 2, 10, 4, 12, 6, 14,
				0, 8, 2, 10, 4, 12, 6, 14,
			};
			uint8_t *chrominances;
			Outputs::CRT::DisplayType display_type;

			switch(output_mode)
			{
				case OutputMode::PAL:
					chrominances = pal_chrominances;
					display_type = Outputs::CRT::PAL50;
					timing_.cycles_per_line = 71;
					timing_.line_counter_increment_offset = 0;
					timing_.lines_per_progressive_field = 312;
					timing_.supports_interlacing = false;
				break;

				case OutputMode::NTSC:
					chrominances = ntsc_chrominances;
					display_type = Outputs::CRT::NTSC60;
					timing_.cycles_per_line = 65;
					timing_.line_counter_increment_offset = 65 - 33;	// TODO: this is a bit of a hack; separate vertical and horizontal counting
					timing_.lines_per_progressive_field = 261;
					timing_.supports_interlacing = true;
				break;
			}

			crt_->set_new_display_type((unsigned int)(timing_.cycles_per_line*4), display_type);
//			crt_->set_visible_area(Outputs::CRT::Rect(0.1f, 0.1f, 0.8f, 0.8f));

//			switch(output_mode)
//			{
//				case OutputMode::PAL:
//					crt_->set_visible_area(crt_->get_rect_for_area(16, 237, 15*4, 55*4, 4.0f / 3.0f));
//				break;
//				case OutputMode::NTSC:
//					crt_->set_visible_area(crt_->get_rect_for_area(16, 237, 11*4, 55*4, 4.0f / 3.0f));
//				break;
//			}

			for(int c = 0; c < 16; c++)
			{
				colours_[c] = (uint8_t)((luminances[c] << 4) | chrominances[c]);
			}
		}

		/*!
			Runs for cycles. Derr.
		*/
		inline void run_for_cycles(unsigned int number_of_cycles)
		{
			// keep track of the amount of time since the speaker was updated; lazy updates are applied
			cycles_since_speaker_update_ += number_of_cycles;

			while(number_of_cycles--)
			{
				// keep an old copy of the vertical count because that test is a cycle later than the actual changes
				int previous_vertical_counter = vertical_counter_;

				// keep track of internal time relative to this scanline
				horizontal_counter_++;
				full_frame_counter_++;
				if(horizontal_counter_ == timing_.cycles_per_line)
				{
					if(horizontal_drawing_latch_)
					{
						current_character_row_++;
						if(
							(current_character_row_ == 16) ||
							(current_character_row_ == 8 && !registers_.tall_characters)
						) {
							current_character_row_ = 0;
							current_row_++;
						}

						pixel_line_cycle_ = -1;
						columns_this_line_ = -1;
						column_counter_ = -1;
					}

					horizontal_counter_ = 0;
					if(output_mode_ == OutputMode::PAL) is_odd_line_ ^= true;
					horizontal_drawing_latch_ = false;

					vertical_counter_ ++;
					if(vertical_counter_ == (registers_.interlaced ? (is_odd_frame_ ? 262 : 263) : timing_.lines_per_progressive_field))
					{
						vertical_counter_ = 0;
						full_frame_counter_ = 0;

						if(output_mode_ == OutputMode::NTSC) is_odd_frame_ ^= true;
						current_row_ = 0;
						rows_this_field_ = -1;
						vertical_drawing_latch_ = false;
						base_video_matrix_address_counter_ = 0;
						current_character_row_ = 0;
					}
				}

				// check for vertical starting events
				vertical_drawing_latch_ |= registers_.first_row_location == (previous_vertical_counter >> 1);
				horizontal_drawing_latch_ |= vertical_drawing_latch_ && (horizontal_counter_ == registers_.first_column_location);

				if(pixel_line_cycle_ >= 0) pixel_line_cycle_++;
				switch(pixel_line_cycle_)
				{
					case -1:
						if(horizontal_drawing_latch_)
						{
							pixel_line_cycle_ = 0;
							video_matrix_address_counter_ = base_video_matrix_address_counter_;
						}
					break;
					case 1:	columns_this_line_ = registers_.number_of_columns;	break;
					case 2:	if(rows_this_field_ < 0) rows_this_field_ = registers_.number_of_rows;	break;
					case 3: if(current_row_ < rows_this_field_) column_counter_ = 0;	break;
				}

				uint16_t fetch_address = 0x1c;
				if(column_counter_ >= 0 && column_counter_ < columns_this_line_*2)
				{
					if(column_counter_&1)
					{
						fetch_address = registers_.character_cell_start_address + (character_code_*(registers_.tall_characters ? 16 : 8)) + current_character_row_;
					}
					else
					{
						fetch_address = (uint16_t)(registers_.video_matrix_start_address + video_matrix_address_counter_);
						video_matrix_address_counter_++;
						if(
							(current_character_row_ == 15) ||
							(current_character_row_ == 7 && !registers_.tall_characters)
						) {
							base_video_matrix_address_counter_ = video_matrix_address_counter_;
						}
					}
				}

				fetch_address &= 0x3fff;

				uint8_t pixel_data;
				uint8_t colour_data;
				static_cast<T *>(this)->perform_read(fetch_address, &pixel_data, &colour_data);

				// TODO: there should be a further two-cycle delay on pixels being output; the reverse bit should
				// divide the byte it is set for 3:1 and then continue as usual.

				// determine output state; colour burst and sync timing are currently a guess
				if(horizontal_counter_ > timing_.cycles_per_line-4) this_state_ = State::ColourBurst;
				else if(horizontal_counter_ > timing_.cycles_per_line-7) this_state_ = State::Sync;
				else
				{
					this_state_ = (column_counter_ >= 0 && column_counter_ < columns_this_line_*2) ? State::Pixels : State::Border;
				}

				// apply vertical sync
				if(
					(vertical_counter_ < 3 && (is_odd_frame_ || !registers_.interlaced)) ||
					(registers_.interlaced &&
						(
							(vertical_counter_ == 0 && horizontal_counter_ > 32) ||
							(vertical_counter_ == 1) || (vertical_counter_ == 2) ||
							(vertical_counter_ == 3 && horizontal_counter_ <= 32)
						)
					))
					this_state_ = State::Sync;

				// update the CRT
				if(this_state_ != output_state_)
				{
					switch(output_state_)
					{
						case State::Sync:			crt_->output_sync(cycles_in_state_ * 4);														break;
						case State::ColourBurst:	crt_->output_colour_burst(cycles_in_state_ * 4, (is_odd_frame_ || is_odd_line_) ? 128 : 0, 0);	break;
						case State::Border:			output_border(cycles_in_state_ * 4);															break;
						case State::Pixels:			crt_->output_data(cycles_in_state_ * 4, 1);														break;
					}
					output_state_ = this_state_;
					cycles_in_state_ = 0;

					pixel_pointer = nullptr;
					if(output_state_ == State::Pixels)
					{
						pixel_pointer = crt_->allocate_write_area(260);
					}
				}
				cycles_in_state_++;

				if(this_state_ == State::Pixels)
				{
					if(column_counter_&1)
					{
						character_value_ = pixel_data;

						if(pixel_pointer)
						{
							uint8_t cell_colour = colours_[character_colour_ & 0x7];
							if(!(character_colour_&0x8))
							{
								uint8_t colours[2];
								if(registers_.invertedCells)
								{
									colours[0] = cell_colour;
									colours[1] = registers_.backgroundColour;
								}
								else
								{
									colours[0] = registers_.backgroundColour;
									colours[1] = cell_colour;
								}
								pixel_pointer[0] = colours[(character_value_ >> 7)&1];
								pixel_pointer[1] = colours[(character_value_ >> 6)&1];
								pixel_pointer[2] = colours[(character_value_ >> 5)&1];
								pixel_pointer[3] = colours[(character_value_ >> 4)&1];
								pixel_pointer[4] = colours[(character_value_ >> 3)&1];
								pixel_pointer[5] = colours[(character_value_ >> 2)&1];
								pixel_pointer[6] = colours[(character_value_ >> 1)&1];
								pixel_pointer[7] = colours[(character_value_ >> 0)&1];
							}
							else
							{
								uint8_t colours[4] = {registers_.backgroundColour, registers_.borderColour, cell_colour, registers_.auxiliary_colour};
								pixel_pointer[0] =
								pixel_pointer[1] = colours[(character_value_ >> 6)&3];
								pixel_pointer[2] =
								pixel_pointer[3] = colours[(character_value_ >> 4)&3];
								pixel_pointer[4] =
								pixel_pointer[5] = colours[(character_value_ >> 2)&3];
								pixel_pointer[6] =
								pixel_pointer[7] = colours[(character_value_ >> 0)&3];
							}
							pixel_pointer += 8;
						}
					}
					else
					{
						character_code_ = pixel_data;
						character_colour_ = colour_data;
					}

					column_counter_++;
				}
			}
		}

		/*!
			Causes the 6560 to flush as much pending CRT and speaker communications as possible.
		*/
		inline void synchronise() { update_audio(); speaker_->flush(); }

		/*!
			Writes to a 6560 register.
		*/
		void set_register(int address, uint8_t value)
		{
			address &= 0xf;
			registers_.direct_values[address] = value;
			switch(address)
			{
				case 0x0:
					registers_.interlaced = !!(value&0x80) && timing_.supports_interlacing;
					registers_.first_column_location = value & 0x7f;
				break;

				case 0x1:
					registers_.first_row_location = value;
				break;

				case 0x2:
					registers_.number_of_columns = value & 0x7f;
					registers_.video_matrix_start_address = (uint16_t)((registers_.video_matrix_start_address & 0x3c00) | ((value & 0x80) << 2));
				break;

				case 0x3:
					registers_.number_of_rows = (value >> 1)&0x3f;
					registers_.tall_characters = !!(value&0x01);
				break;

				case 0x5:
					registers_.character_cell_start_address = (uint16_t)((value & 0x0f) << 10);
					registers_.video_matrix_start_address = (uint16_t)((registers_.video_matrix_start_address & 0x0200) | ((value & 0xf0) << 6));
				break;

				case 0xa:
				case 0xb:
				case 0xc:
				case 0xd:
					update_audio();
					speaker_->set_control(address - 0xa, value);
				break;

				case 0xe:
					update_audio();
					registers_.auxiliary_colour = colours_[value >> 4];
					speaker_->set_volume(value & 0xf);
				break;

				case 0xf:
				{
					uint8_t new_border_colour = colours_[value & 0x07];
					if(this_state_ == State::Border && new_border_colour != registers_.borderColour)
					{
						output_border(cycles_in_state_ * 4);
						cycles_in_state_ = 0;
					}
					registers_.invertedCells = !((value >> 3)&1);
					registers_.borderColour = new_border_colour;
					registers_.backgroundColour = colours_[value >> 4];
				}
				break;

				// TODO: the lightpen, etc

				default:
				break;
			}
		}

		/*
			Reads from a 6560 register.
		*/
		uint8_t get_register(int address)
		{
			address &= 0xf;
			int current_line = (full_frame_counter_ + timing_.line_counter_increment_offset) / timing_.cycles_per_line;
			switch(address)
			{
				default: return registers_.direct_values[address];
				case 0x03: return (uint8_t)(current_line << 7) | (registers_.direct_values[3] & 0x7f);
				case 0x04: return (current_line >> 1) & 0xff;
			}
		}

	private:
		std::shared_ptr<Outputs::CRT::CRT> crt_;

		std::shared_ptr<Speaker> speaker_;
		unsigned int cycles_since_speaker_update_;
		void update_audio()
		{
			speaker_->run_for_cycles(cycles_since_speaker_update_ >> 2);
			cycles_since_speaker_update_ &= 3;
		}

		// register state
		struct {
			bool interlaced, tall_characters;
			uint8_t first_column_location, first_row_location;
			uint8_t number_of_columns, number_of_rows;
			uint16_t character_cell_start_address, video_matrix_start_address;
			uint8_t backgroundColour, borderColour, auxiliary_colour;
			bool invertedCells;

			uint8_t direct_values[16];
		} registers_;

		// output state
		enum State {
			Sync, ColourBurst, Border, Pixels
		} this_state_, output_state_;
		unsigned int cycles_in_state_;

		// counters that cover an entire field
		int horizontal_counter_, vertical_counter_, full_frame_counter_;

		// latches dictating start and length of drawing
		bool vertical_drawing_latch_, horizontal_drawing_latch_;
		int rows_this_field_, columns_this_line_;

		// current drawing position counter
		int pixel_line_cycle_, column_counter_;
		int current_row_;
		uint16_t current_character_row_;
		uint16_t video_matrix_address_counter_, base_video_matrix_address_counter_;

		// data latched from the bus
		uint8_t character_code_, character_colour_, character_value_;

		bool is_odd_frame_, is_odd_line_;

		// lookup table from 6560 colour index to appropriate PAL/NTSC value
		uint8_t colours_[16];

		uint8_t *pixel_pointer;
		void output_border(unsigned int number_of_cycles)
		{
			uint8_t *colour_pointer = crt_->allocate_write_area(1);
			if(colour_pointer) *colour_pointer = registers_.borderColour;
			crt_->output_level(number_of_cycles);
		}

		struct {
			int cycles_per_line;
			int line_counter_increment_offset;
			int lines_per_progressive_field;
			bool supports_interlacing;
		} timing_;
		OutputMode output_mode_;
};

}

#endif /* _560_hpp */