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83 lines
2.1 KiB
C++
83 lines
2.1 KiB
C++
//
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// 6526.h
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// Clock Signal
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//
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// Created by Thomas Harte on 18/07/2021.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#ifndef _526_h
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#define _526_h
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#include <cstdint>
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#include "Implementation/6526Storage.hpp"
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namespace MOS {
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namespace MOS6526 {
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enum Port {
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A = 0,
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B = 1
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};
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struct PortHandler {
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/// Requests the current input value of @c port from the port handler.
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uint8_t get_port_input([[maybe_unused]] Port port) {
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return 0xff;
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}
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/// Sets the current output value of @c port; any bits marked as input will be supplied as 1s.
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void set_port_output([[maybe_unused]] Port port, [[maybe_unused]] uint8_t value) {}
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};
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enum class Personality {
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// The 6526, used in machines such as the C64, has a BCD time-of-day clock.
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P6526,
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// The 8250, used in the Amiga, provides a binary time-of-day clock.
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P8250,
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};
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template <typename PortHandlerT, Personality personality> class MOS6526:
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private MOS6526Storage
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{
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public:
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MOS6526(PortHandlerT &port_handler) noexcept : port_handler_(port_handler) {}
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MOS6526(const MOS6526 &) = delete;
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/// Writes @c value to the register at @c address. Only the low two bits of the address are decoded.
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void write(int address, uint8_t value);
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/// Fetches the value of the register @c address. Only the low two bits of the address are decoded.
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uint8_t read(int address);
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/// Pulses Phi2 to advance by the specified number of half cycles.
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void run_for(const HalfCycles half_cycles);
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/// Pulses the TOD input the specified number of times.
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void advance_tod(int count);
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/// @returns @c true if the interrupt output is active, @c false otherwise.
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bool get_interrupt_line();
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/// Sets the current state of the CNT input.
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void set_cnt_input(bool active);
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private:
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PortHandlerT &port_handler_;
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TODStorage<personality == Personality::P8250> tod_;
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template <int port> void set_port_output();
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template <int port> uint8_t get_port_input();
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void update_interrupts();
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void posit_interrupt(uint8_t mask);
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void advance_counters(int);
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};
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}
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}
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#include "Implementation/6526Implementation.hpp"
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#endif /* _526_h */
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