mirror of
https://github.com/TomHarte/CLK.git
synced 2024-07-16 22:28:57 +00:00
135 lines
4.2 KiB
C++
135 lines
4.2 KiB
C++
//
|
|
// CartridgePitfall2.h
|
|
// Clock Signal
|
|
//
|
|
// Created by Thomas Harte on 18/03/2017.
|
|
// Copyright © 2017 Thomas Harte. All rights reserved.
|
|
//
|
|
|
|
#ifndef Atari2600_CartridgePitfall2_hpp
|
|
#define Atari2600_CartridgePitfall2_hpp
|
|
|
|
namespace Atari2600 {
|
|
|
|
class CartridgePitfall2: public Cartridge<CartridgePitfall2> {
|
|
public:
|
|
CartridgePitfall2(const std::vector<uint8_t> &rom) :
|
|
Cartridge(rom),
|
|
random_number_generator_(0),
|
|
featcher_address_{0, 0, 0, 0, 0, 0, 0, 0},
|
|
mask_{0, 0, 0, 0, 0, 0, 0, 0},
|
|
cycles_since_audio_update_(0) {
|
|
rom_ptr_ = rom_.data();
|
|
}
|
|
|
|
void advance_cycles(unsigned int cycles) {
|
|
cycles_since_audio_update_ += cycles;
|
|
}
|
|
|
|
void perform_bus_operation(CPU::MOS6502::BusOperation operation, uint16_t address, uint8_t *value) {
|
|
address &= 0x1fff;
|
|
if(!(address & 0x1000)) return;
|
|
|
|
switch(address) {
|
|
|
|
#pragma mark - Reads
|
|
|
|
// The random number generator
|
|
case 0x1000: case 0x1001: case 0x1002: case 0x1003: case 0x1004:
|
|
if(isReadOperation(operation)) {
|
|
*value = random_number_generator_;
|
|
}
|
|
random_number_generator_ = (uint8_t)(
|
|
(random_number_generator_ << 1) |
|
|
(~( (random_number_generator_ >> 7) ^
|
|
(random_number_generator_ >> 5) ^
|
|
(random_number_generator_ >> 4) ^
|
|
(random_number_generator_ >> 3)
|
|
) & 1));
|
|
break;
|
|
|
|
case 0x1005: case 0x1006: case 0x1007:
|
|
*value = update_audio();
|
|
break;
|
|
|
|
case 0x1008: case 0x1009: case 0x100a: case 0x100b: case 0x100c: case 0x100d: case 0x100e: case 0x100f:
|
|
*value = rom_[8192 + address_for_counter(address & 7)];
|
|
break;
|
|
|
|
case 0x1010: case 0x1011: case 0x1012: case 0x1013: case 0x1014: case 0x1015: case 0x1016: case 0x1017:
|
|
*value = rom_[8192 + address_for_counter(address & 7)] & mask_[address & 7];
|
|
break;
|
|
|
|
#pragma mark - Writes
|
|
|
|
case 0x1040: case 0x1041: case 0x1042: case 0x1043: case 0x1044: case 0x1045: case 0x1046: case 0x1047:
|
|
top_[address & 7] = *value;
|
|
break;
|
|
case 0x1048: case 0x1049: case 0x104a: case 0x104b: case 0x104c: case 0x104d: case 0x104e: case 0x104f:
|
|
bottom_[address & 7] = *value;
|
|
break;
|
|
case 0x1050: case 0x1051: case 0x1052: case 0x1053: case 0x1054: case 0x1055: case 0x1056: case 0x1057:
|
|
featcher_address_[address & 7] = (featcher_address_[address & 7] & 0xff00) | *value;
|
|
mask_[address & 7] = 0x00;
|
|
break;
|
|
case 0x1058: case 0x1059: case 0x105a: case 0x105b: case 0x105c: case 0x105d: case 0x105e: case 0x105f:
|
|
featcher_address_[address & 7] = (featcher_address_[address & 7] & 0x00ff) | (uint16_t)(*value << 8);
|
|
break;
|
|
case 0x1070: case 0x1071: case 0x1072: case 0x1073: case 0x1074: case 0x1075: case 0x1076: case 0x1077:
|
|
random_number_generator_ = 0;
|
|
break;
|
|
|
|
#pragma mark - Paging
|
|
|
|
case 0x1ff8: rom_ptr_ = rom_.data(); break;
|
|
case 0x1ff9: rom_ptr_ = rom_.data() + 4096; break;
|
|
|
|
#pragma mark - Business as usual
|
|
|
|
default:
|
|
if(isReadOperation(operation)) {
|
|
*value = rom_ptr_[address & 4095];
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
|
|
private:
|
|
inline uint16_t address_for_counter(int counter) {
|
|
uint16_t fetch_address = (featcher_address_[counter] & 2047) ^ 2047;
|
|
if((featcher_address_[counter] & 0xff) == top_[counter]) mask_[counter] = 0xff;
|
|
if((featcher_address_[counter] & 0xff) == bottom_[counter]) mask_[counter] = 0x00;
|
|
featcher_address_[counter]--;
|
|
return fetch_address;
|
|
}
|
|
|
|
inline uint8_t update_audio() {
|
|
const unsigned int clock_divisor = 57;
|
|
unsigned int cycles_to_run_for = cycles_since_audio_update_ / clock_divisor;
|
|
cycles_since_audio_update_ %= clock_divisor;
|
|
|
|
int table_position = 0;
|
|
for(int c = 0; c < 3; c++) {
|
|
audio_channel_[c] = (audio_channel_[c] + cycles_to_run_for) % (1 + top_[5 + c]);
|
|
if((featcher_address_[5 + c] & 0x1000) && ((top_[5 + c] - audio_channel_[c]) > bottom_[5 + c])) {
|
|
table_position |= 0x4 >> c;
|
|
}
|
|
}
|
|
|
|
static uint8_t level_table[8] = { 0x0, 0x4, 0x5, 0x9, 0x6, 0xa, 0xb, 0xf };
|
|
return level_table[table_position];
|
|
}
|
|
|
|
uint16_t featcher_address_[8];
|
|
uint8_t top_[8], bottom_[8], mask_[8];
|
|
uint8_t music_mode_[3];
|
|
uint8_t random_number_generator_;
|
|
uint8_t *rom_ptr_;
|
|
uint8_t audio_channel_[3];
|
|
unsigned int cycles_since_audio_update_;
|
|
};
|
|
|
|
}
|
|
|
|
#endif /* Atari2600_CartridgePitfall2_hpp */
|