mirror of https://github.com/TomHarte/CLK.git
109 lines
2.5 KiB
C++
109 lines
2.5 KiB
C++
//
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// 6522Storage.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 04/09/2017.
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// Copyright 2017 Thomas Harte. All rights reserved.
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//
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#pragma once
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#include <cstdint>
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namespace MOS::MOS6522 {
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class MOS6522Storage {
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protected:
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// Phase toggle
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bool is_phase2_ = false;
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// The registers
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struct Registers {
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// "A low reset (RES) input clears all R6522 internal registers to logic 0"
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uint8_t output[2] = {0, 0};
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uint8_t input[2] = {0, 0};
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uint8_t data_direction[2] = {0, 0};
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uint16_t timer[2] = {0, 0};
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uint16_t timer_latch[2] = {0, 0};
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uint16_t last_timer[2] = {0, 0};
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int next_timer[2] = {-1, -1};
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uint8_t shift = 0;
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uint8_t auxiliary_control = 0;
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uint8_t peripheral_control = 0;
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uint8_t interrupt_flags = 0;
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uint8_t interrupt_enable = 0;
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bool timer_needs_reload = false;
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uint8_t timer_port_b_output = 0xff;
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} registers_;
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// Control state.
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struct {
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bool lines[2] = {false, false};
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} control_inputs_[2];
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enum class LineState {
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On, Off, Input
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};
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struct {
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LineState lines[2] = {LineState::Input, LineState::Input};
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} control_outputs_[2];
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enum class HandshakeMode {
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None,
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Handshake,
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Pulse
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} handshake_modes_[2] = { HandshakeMode::None, HandshakeMode::None };
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bool timer_is_running_[2] = {false, false};
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bool last_posted_interrupt_status_ = false;
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int shift_bits_remaining_ = 8;
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enum InterruptFlag: uint8_t {
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CA2ActiveEdge = 1 << 0,
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CA1ActiveEdge = 1 << 1,
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ShiftRegister = 1 << 2,
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CB2ActiveEdge = 1 << 3,
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CB1ActiveEdge = 1 << 4,
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Timer2 = 1 << 5,
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Timer1 = 1 << 6,
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};
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enum class ShiftMode {
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Disabled = 0,
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InUnderT2 = 1,
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InUnderPhase2 = 2,
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InUnderCB1 = 3,
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OutUnderT2FreeRunning = 4,
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OutUnderT2 = 5,
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OutUnderPhase2 = 6,
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OutUnderCB1 = 7
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};
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bool timer1_is_controlling_pb7() const {
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return registers_.auxiliary_control & 0x80;
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}
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bool timer1_is_continuous() const {
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return registers_.auxiliary_control & 0x40;
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}
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bool is_shifting_out() const {
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return registers_.auxiliary_control & 0x10;
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}
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int timer2_clock_decrement() const {
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return 1 ^ ((registers_.auxiliary_control >> 5)&1);
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}
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int timer2_pb6_decrement() const {
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return (registers_.auxiliary_control >> 5)&1;
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}
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ShiftMode shift_mode() const {
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return ShiftMode((registers_.auxiliary_control >> 2) & 7);
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}
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bool portb_is_latched() const {
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return registers_.auxiliary_control & 0x02;
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}
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bool port1_is_latched() const {
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return registers_.auxiliary_control & 0x01;
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}
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};
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}
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