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https://github.com/TomHarte/CLK.git
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Gets as far as executing a first loop.
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Thomas Harte
parent
e502d76371
commit
e58608b25a
@ -118,9 +118,10 @@ template <
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// }
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}
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void perform_all() {
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// TEMPORARY (?). Execute all current instructions, unless
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// and until one branches.
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/*!
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Executes up to the next branch.
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*/
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void run_to_branch() {
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has_branched_ = false;
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for(auto index: program_) {
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const auto performer = performers_[index];
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@ -37,7 +37,9 @@ void Executor::set_rom(const std::vector<uint8_t> &rom) {
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reset();
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// TEMPORARY: just to test initial wiring.
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perform_all();
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for(int c = 0; c < 130; c++) {
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run_to_branch();
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}
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}
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void Executor::reset() {
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@ -45,6 +47,49 @@ void Executor::reset() {
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set_program_counter(uint16_t(memory_[0x1ffe] | (memory_[0x1fff] << 8)));
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}
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uint8_t Executor::read(uint16_t address) {
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address &= 0x1fff;
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switch(address) {
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default: return memory_[address];
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// TODO: external IO ports.
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// "Port R"; sixteen four-bit ports
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case 0xd0: case 0xd1: case 0xd2: case 0xd3: case 0xd4: case 0xd5: case 0xd6: case 0xd7:
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case 0xd8: case 0xd9: case 0xda: case 0xdb: case 0xdc: case 0xdd: case 0xde: case 0xdf:
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printf("TODO: Port R\n");
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return 0xff;
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// Ports P0–P3.
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case 0xe0: case 0xe1:
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case 0xe2: case 0xe3:
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case 0xe4: case 0xe5:
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case 0xe8: case 0xe9:
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printf("TODO: Ports P0–P3\n");
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return 0xff;
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// Timers.
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case 0xf9: case 0xfa: case 0xfb: case 0xfc: case 0xfd: case 0xfe: case 0xff:
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printf("TODO: Timers\n");
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return 0xff;
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}
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}
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void Executor::write(uint16_t address, uint8_t value) {
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address &= 0x1fff;
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if(address < 0x60) {
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memory_[address] = value;
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return;
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}
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// TODO: all external IO ports.
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}
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void Executor::push(uint8_t value) {
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write(s_, value);
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--s_;
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}
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template <Operation operation, AddressingMode addressing_mode> void Executor::perform() {
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// Deal with all modes that don't access memory up here;
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// those that access memory will go through a slightly longer
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@ -55,7 +100,7 @@ template <Operation operation, AddressingMode addressing_mode> void Executor::pe
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#define next8() memory_[(program_counter_ + 1) & 0x1fff]
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#define next16() (memory_[(program_counter_ + 1) & 0x1fff] | (memory_[(program_counter_ + 2) & 0x1fff] << 8))
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printf("%d %d\n", int(operation), int(addressing_mode));
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printf("%04x\t%d %d\n", program_counter_ & 0x1fff, int(operation), int(addressing_mode));
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// Underlying assumption below: the instruction stream will never
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// overlap with IO ports.
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@ -78,17 +123,19 @@ template <Operation operation, AddressingMode addressing_mode> void Executor::pe
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program_counter_ += 2;
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return;
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// case AddressingMode::Relative:
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// These are all the branches...
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// address = program_counter_ + size(addressing_mode) + int8_t(next8());
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// return;
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// Special-purpose addressing modes.
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// case AddressingMode::ImmediateZeroPage:
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case AddressingMode::Relative:
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address = program_counter_ + 1 + size(addressing_mode) + int8_t(next8());
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break;
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case AddressingMode::SpecialPage: address = 0x1f00 | next8(); break;
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case AddressingMode::ImmediateZeroPage:
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// LDM only...
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// return;
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// case AddressingMode::SpecialPage: address = 0x1f00 | next8(); break;
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// JSR only...
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write(memory_[(program_counter_+2)&0x1fff], memory_[(program_counter_+1)&0x1fff]);
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program_counter_ += 1 + size(addressing_mode);
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return;
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/* TODO:
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@ -136,16 +183,23 @@ template <Operation operation, AddressingMode addressing_mode> void Executor::pe
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// Check for a branch; those don't go through the memory accesses below.
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switch(operation) {
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case Operation::JMP:
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case Operation::BRA: case Operation::JMP:
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set_program_counter(uint16_t(address));
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return;
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case Operation::JSR:
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// TODO: push!
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case Operation::JSR: {
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const auto return_address = program_counter_ - 1;
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push(uint8_t(return_address >> 8));
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push(uint8_t(return_address & 0xff));
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set_program_counter(uint16_t(address));
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return;
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} return;
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/* TODO: all other types of branches and calls. */
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case Operation::BPL: if(!(negative_result_&0x80)) set_program_counter(uint16_t(address)); return;
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case Operation::BMI: if(negative_result_&0x80) set_program_counter(uint16_t(address)); return;
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case Operation::BEQ: if(!zero_result_) set_program_counter(uint16_t(address)); return;
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case Operation::BNE: if(zero_result_) set_program_counter(uint16_t(address)); return;
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/* TODO: all other types of branches. */
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default: break;
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}
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@ -153,18 +207,20 @@ template <Operation operation, AddressingMode addressing_mode> void Executor::pe
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assert(access_type(operation) != AccessType::None);
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// TODO: full reading/writing logic here; only the first 96 bytes are RAM,
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// there are also timers and IO ports to handle.
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if constexpr(access_type(operation) == AccessType::Read) {
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perform<operation>(&memory_[address & 0x1fff]);
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uint8_t source = read(uint16_t(address));
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perform<operation>(&source);
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return;
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}
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uint8_t value = memory_[address & 0x1fff];
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uint8_t value;
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if constexpr(access_type(operation) == AccessType::ReadModifyWrite) {
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value = read(uint16_t(address));
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} else {
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value = 0xff;
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}
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perform<operation>(&value);
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memory_[address & 0x1fff] = value;
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write(uint16_t(address), value);
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}
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template <Operation operation> void Executor::perform(uint8_t *operand [[maybe_unused]]) {
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@ -201,6 +257,20 @@ template <Operation operation> void Executor::perform(uint8_t *operand [[maybe_u
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case Operation::CLD: decimal_mode_ = false; break;
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case Operation::SED: decimal_mode_ = true; break;
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case Operation::DEX: --x_; set_nz(x_); break;
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case Operation::INX: ++x_; set_nz(x_); break;
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case Operation::DEY: --y_; set_nz(y_); break;
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case Operation::INY: ++y_; set_nz(y_); break;
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case Operation::DEC: --*operand; set_nz(*operand); break;
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case Operation::INC: ++*operand; set_nz(*operand); break;
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/*
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Already removed from the instruction stream:
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* all branches and jumps;
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* LDM.
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*/
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default:
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printf("Unimplemented operation: %d\n", int(operation));
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assert(false);
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@ -209,6 +279,7 @@ template <Operation operation> void Executor::perform(uint8_t *operand [[maybe_u
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}
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void Executor::set_program_counter(uint16_t address) {
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printf("--- %04x ---\n", (address & 0x1fff) - 0x1000);
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program_counter_ = address;
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CachingExecutor::set_program_counter(address);
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}
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@ -117,6 +117,10 @@ class Executor: public CachingExecutor {
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uint8_t interrupt_disable_ = 0;
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bool index_mode_ = false;
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bool decimal_mode_ = false;
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inline uint8_t read(uint16_t address);
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inline void write(uint16_t address, uint8_t value);
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inline void push(uint8_t value);
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};
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}
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