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Attempts to rationalise Apple II address decoding.
This commit is contained in:
Thomas Harte
parent
9ff34d90f4
commit
4c4ab25d0e
@ -72,7 +72,6 @@ class ConcreteMachine:
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uint8_t ram_[48*1024];
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std::vector<uint8_t> apple2_rom_, apple2plus_rom_, rom_;
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std::vector<uint8_t> character_rom_;
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uint16_t rom_start_address_;
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uint8_t keyboard_input_ = 0x00;
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Concurrency::DeferringAsyncTaskQueue audio_queue_;
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@ -85,6 +84,11 @@ class ConcreteMachine:
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Cycles cycles_since_card_update_;
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int stretched_cycles_since_card_update_ = 0;
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struct MemoryBlock {
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uint8_t *read_pointer = nullptr;
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uint8_t *write_pointer = nullptr;
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} memory_blocks_[4]; // The IO page isn't included.
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public:
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ConcreteMachine():
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m6502_(*this),
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@ -129,72 +133,82 @@ class ConcreteMachine:
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++ cycles_since_card_update_;
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cycles_since_audio_update_ += Cycles(7);
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switch(address) {
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default:
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if(isReadOperation(operation)) {
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if(address < sizeof(ram_)) {
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*value = ram_[address];
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} else if(address >= rom_start_address_) {
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*value = rom_[address - rom_start_address_];
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} else {
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/*
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There are five distinct zones of memory on an Apple II:
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0000 — 0200 : the zero and stack pages, which can be paged independently on a IIe
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0200 — c000 : the main block of RAM, which can be paged on a IIe
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c000 — d000 : the IO area, including card ROMs
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d000 — e000 : the low ROM area, which can contain indepdently-paged RAM with a language card
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e000 — : the rest of ROM, also potentially replaced with RAM by a language card
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*/
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MemoryBlock *block = nullptr;
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if(address < 0x200) block = &memory_blocks_[0];
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else if(address < 0xc000) {update_video(); block = &memory_blocks_[1]; address -= 0x200; }
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else if(address < 0xd000) block = nullptr;
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else if(address < 0xe000) {block = &memory_blocks_[2]; address -= 0xd000; }
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else {block = &memory_blocks_[3]; address -= 0xe000; }
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if(block) {
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if(isReadOperation(operation)) *value = block->read_pointer[address];
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else if(block->write_pointer) block->write_pointer[address] = *value;
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} else {
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switch(address) {
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default:
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if(isReadOperation(operation)) {
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// Read-only switches.
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switch(address) {
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default:
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// printf("Unknown access to %04x\n", address);
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break;
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default: break;
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case 0xc000:
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*value = keyboard_input_;
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break;
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}
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} else {
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// Write-only switches.
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}
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} else {
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if(address < sizeof(ram_)) {
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if(address >= 0x400) {
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// TODO: be more selective.
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update_video();
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}
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ram_[address] = *value;
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}
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}
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break;
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break;
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case 0xc050: update_video(); video_->set_graphics_mode(); break;
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case 0xc051: update_video(); video_->set_text_mode(); break;
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case 0xc052: update_video(); video_->set_mixed_mode(false); break;
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case 0xc053: update_video(); video_->set_mixed_mode(true); break;
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case 0xc054: update_video(); video_->set_video_page(0); break;
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case 0xc055: update_video(); video_->set_video_page(1); break;
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case 0xc056: update_video(); video_->set_low_resolution(); break;
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case 0xc057: update_video(); video_->set_high_resolution(); break;
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/* Read-write switches. */
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case 0xc050: update_video(); video_->set_graphics_mode(); break;
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case 0xc051: update_video(); video_->set_text_mode(); break;
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case 0xc052: update_video(); video_->set_mixed_mode(false); break;
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case 0xc053: update_video(); video_->set_mixed_mode(true); break;
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case 0xc054: update_video(); video_->set_video_page(0); break;
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case 0xc055: update_video(); video_->set_video_page(1); break;
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case 0xc056: update_video(); video_->set_low_resolution(); break;
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case 0xc057: update_video(); video_->set_high_resolution(); break;
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case 0xc010:
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keyboard_input_ &= 0x7f;
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break;
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case 0xc010:
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keyboard_input_ &= 0x7f;
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break;
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case 0xc030:
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update_audio();
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audio_toggle_.set_output(!audio_toggle_.get_output());
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break;
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}
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if(address >= 0xc100 && address < 0xc800) {
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/*
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Decode the area conventionally used by cards for ROMs:
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0xCn00 — 0xCnff: card n.
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*/
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const int card_number = (address - 0xc100) >> 8;
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if(cards_[card_number]) {
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update_cards();
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cards_[card_number]->perform_bus_operation(operation, address & 0xff, value);
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case 0xc030:
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update_audio();
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audio_toggle_.set_output(!audio_toggle_.get_output());
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break;
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}
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} else if(address >= 0xc090 && address < 0xc100) {
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/*
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Decode the area conventionally used by cards for registers:
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C0n0--C0nF: card n - 8.
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*/
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const int card_number = (address - 0xc090) >> 4;
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if(cards_[card_number]) {
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update_cards();
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cards_[card_number]->perform_bus_operation(operation, 0x100 | (address&0xf), value);
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if(address >= 0xc100 && address < 0xc800) {
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/*
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Decode the area conventionally used by cards for ROMs:
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0xCn00 — 0xCnff: card n.
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*/
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const int card_number = (address - 0xc100) >> 8;
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if(cards_[card_number]) {
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update_cards();
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cards_[card_number]->perform_bus_operation(operation, address & 0xff, value);
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}
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} else if(address >= 0xc090 && address < 0xc100) {
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/*
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Decode the area conventionally used by cards for registers:
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C0n0--C0nF: card n - 8.
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*/
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const int card_number = (address - 0xc090) >> 4;
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if(cards_[card_number]) {
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update_cards();
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cards_[card_number]->perform_bus_operation(operation, 0x100 | (address&0xf), value);
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}
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}
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}
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@ -283,7 +297,12 @@ class ConcreteMachine:
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if(rom_.size() > 12*1024) {
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rom_.erase(rom_.begin(), rom_.begin() + static_cast<off_t>(rom_.size()) - 12*1024);
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}
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rom_start_address_ = 0xd000;//static_cast<uint16_t>(0x10000 - rom_.size());
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// Set up the default memory blocks.
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memory_blocks_[0].read_pointer = memory_blocks_[0].write_pointer = ram_;
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memory_blocks_[1].read_pointer = memory_blocks_[1].write_pointer = &ram_[0x200];
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memory_blocks_[2].read_pointer = rom_.data();
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memory_blocks_[3].read_pointer = rom_.data() + 0x1000;
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insert_media(apple_target->media);
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}
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