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353 lines
11 KiB
C++
353 lines
11 KiB
C++
//
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// Atari2600.cpp
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// CLK
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//
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// Created by Thomas Harte on 14/07/2015.
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// Copyright © 2015 Thomas Harte. All rights reserved.
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//
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#include "Atari2600.hpp"
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#include <algorithm>
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#include <stdio.h>
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using namespace Atari2600;
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static const char atari2600DataType[] = "Atari2600";
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static const int horizontalTimerReload = 227;
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Machine::Machine()
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{
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_timestamp = 0;
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_horizontalTimer = horizontalTimerReload;
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_lastOutputStateDuration = 0;
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_lastOutputState = OutputState::Sync;
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_crt = new Outputs::CRT(228, 262, 1, 4);
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_piaTimerStatus = 0xff;
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setup6502();
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}
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Machine::~Machine()
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{
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delete _crt;
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}
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void Machine::switch_region()
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{
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_crt->set_new_timing(228, 312);
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}
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void Machine::get_output_pixel(uint8_t *pixel, int offset)
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{
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const uint8_t palette[16][3] =
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{
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{255, 255, 255}, {253, 250, 115}, {236, 199, 125}, {252, 187, 151},
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{252, 180, 181}, {235, 177, 223}, {211, 178, 250}, {187, 182, 250},
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{164, 186, 250}, {166, 201, 250}, {164, 224, 251}, {165, 251, 213},
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{185, 251, 187}, {201, 250, 168}, {225, 235, 160}, {252, 223, 145}
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};
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const uint8_t alphaValues[8] =
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{
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// 0, 64, 108, 144, 176, 200, 220, 255
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// };
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//
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// {
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69, 134, 108, 161, 186, 210, 235, 255
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};
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// get the playfield pixel and hence a proposed colour
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const int x = offset >> 2;
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const int mirrored = (x / 20) & (_playfieldControl&1);
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const int index = mirrored ? x - 20 : 19 - (x%20);
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const int byte = 2 - (index >> 3);
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const int lowestBit = (byte&1)^1;
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const int bit = (index & 7)^(lowestBit | (lowestBit << 1) | (lowestBit << 2));
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uint8_t playfieldPixel = (_playfield[byte] >> bit)&1;
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uint8_t playfieldColour = ((_playfieldControl&6) == 2) ? _playerColour[x / 20] : _playfieldColour;
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// get player and missile proposed pixels
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uint8_t playerPixels[2], missilePixels[2];
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for(int c = 0; c < 2; c++)
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{
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// figure out player colour
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int flipMask = (_playerReflection[c]&0x8) ? 0 : 7;
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int relativeTimer = _playerPosition[c] - _horizontalTimer;
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switch (_playerAndMissileSize[c]&7)
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{
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case 0: break;
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case 1:
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if (relativeTimer >= 16) relativeTimer -= 16;
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break;
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case 2:
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if (relativeTimer >= 32) relativeTimer -= 32;
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break;
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case 3:
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if (relativeTimer >= 32) relativeTimer -= 32;
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else if (relativeTimer >= 16) relativeTimer -= 16;
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break;
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case 4:
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if (relativeTimer >= 64) relativeTimer -= 64;
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break;
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case 5:
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relativeTimer >>= 1;
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break;
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case 6:
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if (relativeTimer >= 64) relativeTimer -= 64;
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else if (relativeTimer >= 32) relativeTimer -= 32;
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break;
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case 7:
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relativeTimer >>= 2;
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break;
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}
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if(relativeTimer >= 0 && relativeTimer < 8)
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playerPixels[c] = (_playerGraphics[c] >> (relativeTimer ^ flipMask)) &1;
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else
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playerPixels[c] = 0;
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// figure out missile colour
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int missileIndex = _missilePosition[c] - _horizontalTimer;
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int missileSize = 1 << ((_playerAndMissileSize[c] >> 4)&3);
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missilePixels[c] = (missileIndex >= 0 && missileIndex < missileSize && (_missileGraphicsEnable[c]&2)) ? 1 : 0;
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}
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// get the ball proposed colour
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uint8_t ballPixel;
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int ballIndex = _ballPosition - _horizontalTimer;
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int ballSize = 1 << ((_playfieldControl >> 4)&3);
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ballPixel = (ballIndex >= 0 && ballIndex < ballSize && (_ballGraphicsEnable&2)) ? 1 : 0;
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// apply appropriate priority to pick a colour
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playfieldPixel |= ballPixel;
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uint8_t outputColour = playfieldPixel ? playfieldColour : _backgroundColour;
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if(!(_playfieldControl&0x04) || !playfieldPixel) {
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if (playerPixels[1] || missilePixels[1]) outputColour = _playerColour[1];
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if (playerPixels[0] || missilePixels[0]) outputColour = _playerColour[0];
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}
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// map that colour to an RGBA
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pixel[0] = palette[outputColour >> 4][0];
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pixel[1] = palette[outputColour >> 4][1];
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pixel[2] = palette[outputColour >> 4][2];
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pixel[3] = alphaValues[(outputColour >> 1)&7];
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}
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void Machine::output_pixels(int count)
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{
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const int32_t start_of_sync = 214;
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const int32_t end_of_sync = 198;
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_timestamp += count;
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while(count--)
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{
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OutputState state;
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// logic: if in vsync, output that; otherwise if in vblank then output that;
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// otherwise output a pixel
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if(_vSyncEnabled) {
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state = (_horizontalTimer < start_of_sync) ? OutputState::Sync : OutputState::Blank;
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} else {
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// blank is decoded as 68 counts; sync and colour burst as 16 counts
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// 4 blank
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// 4 sync
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// 9 'blank'; colour burst after 4
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// 40 pixels
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// it'll be about 43 cycles from start of hsync to start of visible frame, so...
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// guesses, until I can find information: 26 cycles blank, 16 sync, 40 blank, 160 pixels
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if(_horizontalTimer >= start_of_sync) state = OutputState::Blank;
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else if (_horizontalTimer >= end_of_sync) state = OutputState::Sync;
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else if (_horizontalTimer >= 160) state = OutputState::Blank;
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else {
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if(_vBlankEnabled) {
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state = OutputState::Blank;
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} else {
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state = OutputState::Pixel;
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}
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}
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}
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_lastOutputStateDuration++;
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if(state != _lastOutputState)
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{
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switch(_lastOutputState)
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{
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case OutputState::Blank: _crt->output_blank(_lastOutputStateDuration); break;
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case OutputState::Sync: _crt->output_sync(_lastOutputStateDuration); break;
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case OutputState::Pixel: _crt->output_data(_lastOutputStateDuration, atari2600DataType); break;
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}
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_lastOutputStateDuration = 0;
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_lastOutputState = state;
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if(state == OutputState::Pixel)
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{
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_crt->allocate_write_area(160);
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_outputBuffer = _crt->get_write_target_for_buffer(0);
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}
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}
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if(state == OutputState::Pixel && _outputBuffer)
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get_output_pixel(&_outputBuffer[_lastOutputStateDuration * 4], 159 - _horizontalTimer);
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// assumption here: signed shifts right; otherwise it's just
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// an attempt to avoid both the % operator and a conditional
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_horizontalTimer--;
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const int32_t sign_extension = _horizontalTimer >> 31;
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_horizontalTimer = (_horizontalTimer&~sign_extension) | (sign_extension&horizontalTimerReload);
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}
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}
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int Machine::perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value)
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{
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uint8_t returnValue = 0xff;
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output_pixels(3);
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if(_horizontalTimer == horizontalTimerReload)
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set_ready_line(false);
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if(operation != CPU6502::BusOperation::Ready) {
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// check for a ROM access
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if ((address&0x1000) && isReadOperation(operation)) {
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returnValue &= _rom[address&_romMask];
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}
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// check for a RAM access
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if ((address&0x1280) == 0x80) {
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if(isReadOperation(operation)) {
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returnValue &= _ram[address&0x7f];
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} else {
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_ram[address&0x7f] = *value;
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}
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}
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// check for a TIA access
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if (!(address&0x1080)) {
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if(isReadOperation(operation)) {
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switch(address & 0xf) {
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case 0x00: returnValue &= 0x3f; break; // missile 0 / player collisions
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case 0x01: returnValue &= 0x3f; break; // missile 1 / player collisions
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case 0x02: returnValue &= 0x3f; break; // player 0 / playfield / ball collisions
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case 0x03: returnValue &= 0x3f; break; // player 1 / playfield / ball collisions
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case 0x04: returnValue &= 0x3f; break; // missile 0 / playfield / ball collisions
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case 0x05: returnValue &= 0x3f; break; // missile 1 / playfield / ball collisions
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case 0x06: returnValue &= 0x7f; break; // ball / playfield collisions
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case 0x07: returnValue &= 0x3f; break; // player / player, missile / missile collisions
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}
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} else {
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switch(address & 0x3f) {
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case 0x00: _vSyncEnabled = !!(*value & 0x02); break;
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case 0x01: _vBlankEnabled = !!(*value & 0x02); break;
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case 0x02: {
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set_ready_line(true);
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} break;
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case 0x03: _horizontalTimer = horizontalTimerReload; break;
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case 0x04: _playerAndMissileSize[0] = *value; break;
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case 0x05: _playerAndMissileSize[1] = *value; break;
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case 0x06: _playerColour[0] = *value; break;
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case 0x07: _playerColour[1] = *value; break;
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case 0x08: _playfieldColour = *value; break;
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case 0x09: _backgroundColour = *value; break;
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case 0x0a: _playfieldControl = *value; break;
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case 0x0b: _playerReflection[0] = *value; break;
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case 0x0c: _playerReflection[1] = *value; break;
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case 0x0d: _playfield[0] = *value; break;
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case 0x0e: _playfield[1] = *value; break;
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case 0x0f: _playfield[2] = *value; break;
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case 0x10: _playerPosition[0] = _horizontalTimer - 5; break;
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case 0x11: _playerPosition[1] = _horizontalTimer - 5; break;
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case 0x12: _missilePosition[0] = _horizontalTimer - 4; break;
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case 0x13: _missilePosition[1] = _horizontalTimer - 4; break;
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case 0x14: _ballPosition = _horizontalTimer - 4; break;
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case 0x1c:
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_ballGraphicsEnable = _ballGraphicsEnableLatch;
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case 0x1b: {
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int index = (address & 0x3f) - 0x1b;
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_playerGraphicsLatch[index] = *value;
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if(!(_playerGraphicsLatchEnable[index]&1))
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_playerGraphics[index] = _playerGraphicsLatch[index];
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_playerGraphics[index^1] = _playerGraphicsLatch[index^1];
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} break;
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case 0x1d: _missileGraphicsEnable[0] = *value; break;
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case 0x1e: _missileGraphicsEnable[1] = *value; break;
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case 0x1f:
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_ballGraphicsEnableLatch = *value;
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if(!(_ballGraphicsEnableDelay&1))
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_ballGraphicsEnable = _ballGraphicsEnableLatch;
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break;
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case 0x20: _playerMotion[0] = *value; break;
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case 0x21: _playerMotion[1] = *value; break;
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case 0x22: _missileMotion[0] = *value; break;
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case 0x23: _missileMotion[1] = *value; break;
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case 0x24: _ballMotion = *value; break;
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case 0x25: _playerGraphicsLatchEnable[0] = *value; break;
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case 0x26: _playerGraphicsLatchEnable[1] = *value; break;
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case 0x27: _ballGraphicsEnableDelay = *value; break;
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// case 0x28: _missilePosition[0] = _playerPosition[0]; break;
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case 0x2a:
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_playerPosition[0] += (int8_t)_playerMotion[0] >> 4;
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_playerPosition[1] += (int8_t)_playerMotion[1] >> 4;
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_missilePosition[0] += (int8_t)_missileMotion[0] >> 4;
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_missilePosition[1] += (int8_t)_missileMotion[1] >> 4;
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_ballPosition += (int8_t)_ballMotion >> 4;
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break;
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case 0x2b: _playerMotion[0] = _playerMotion[1] = _missileMotion[0] = _missileMotion[1] = _ballMotion = 0; break;
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}
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}
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// printf("Uncaught TIA %04x\n", address);
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}
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// check for a PIA access
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if ((address&0x1280) == 0x280) {
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if(isReadOperation(operation)) {
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switch(address & 0xf) {
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case 0x04: returnValue &= _piaTimerValue >> _piaTimerShift; break;
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case 0x05: returnValue &= _piaTimerStatus; _piaTimerStatus &= ~0x40; break;
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}
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} else {
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switch(address & 0x0f) {
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case 0x04: _piaTimerShift = 0; _piaTimerValue = *value << 0; _piaTimerStatus &= ~0xc0; break;
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case 0x05: _piaTimerShift = 3; _piaTimerValue = *value << 3; _piaTimerStatus &= ~0xc0; break;
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case 0x06: _piaTimerShift = 6; _piaTimerValue = *value << 6; _piaTimerStatus &= ~0xc0; break;
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case 0x07: _piaTimerShift = 10; _piaTimerValue = *value << 10; _piaTimerStatus &= ~0xc0; break;
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}
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}
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// printf("Uncaught PIA %04x\n", address);
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}
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if(isReadOperation(operation)) {
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*value = returnValue;
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}
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}
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if(_piaTimerValue) {
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_piaTimerValue --;
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} else {
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_piaTimerValue = 0xff;
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_piaTimerShift = 0;
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_piaTimerStatus |= 0xc0;
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}
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return 1;
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}
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void Machine::set_rom(size_t length, const uint8_t *data)
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{
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length = std::min((size_t)4096, length);
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memcpy(_rom, data, length);
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_romMask = length - 1;
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}
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