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162 lines
3.7 KiB
C++
162 lines
3.7 KiB
C++
//
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// 6522.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 06/06/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#ifndef _522_hpp
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#define _522_hpp
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#include <cstdint>
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#include <cstdio>
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namespace MOS {
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class MOS6522Delegate {
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public:
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virtual void mos6522_did_change_interrupt_status(void *mos6522) = 0;
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};
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template <class T> class MOS6522 {
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private:
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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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public:
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void set_delegate(MOS6522Delegate *delegate)
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{
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_delegate = delegate;
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}
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MOS6522() :
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_data_direction{0, 0},
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_timer_is_running{false, false}
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{}
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void set_register(int address, uint8_t value)
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{
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printf("6522: %d <- %02x\n", address, value);
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address &= 0xf;
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switch(address)
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{
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// Timer 1
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case 0x06: case 0x04: _interval_timer_latch[0] = (_interval_timer_latch[0]&0xff00) | value; break;
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case 0x05: case 0x07:
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_interval_timer_latch[0] = (_interval_timer_latch[0]&0x00ff) | (uint16_t)(value << 8);
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_interrupt_flags &= ~InterruptFlag::Timer1;
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if(address == 0x05)
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{
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_interval_timer[0] = _interval_timer_latch[0];
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_timer_is_running[0] = true;
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}
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reevaluate_interrupts();
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break;
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// Timer 2
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case 0x08: _interval_timer_latch[1] = value; break;
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case 0x09:
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_interrupt_flags &= ~InterruptFlag::Timer2;
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_interval_timer[1] = _interval_timer_latch[1] | (uint16_t)(value << 8);
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_timer_is_running[1] = true;
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reevaluate_interrupts();
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break;
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case 11: _auxiliary_control_register = value; break;
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case 13:
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if(!(value&0x80)) value = ~value;
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_interrupt_mask = value;
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break;
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case 14:
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break;
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}
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}
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uint8_t get_register(int address)
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{
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printf("6522: %d\n", address);
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address &= 0xf;
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switch(address)
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{
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// Timer 1
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case 0x04:
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_interrupt_flags &= ~InterruptFlag::Timer1;
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reevaluate_interrupts();
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return _interval_timer[0] & 0x00ff;
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case 0x05: return _interval_timer[0] >> 8;
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case 0x06: return _interval_timer_latch[0] & 0x00ff;
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case 0x07: return _interval_timer_latch[0] >> 8;
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case 11: return _auxiliary_control_register;
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case 13: return _interrupt_flags;
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case 14: return _interrupt_mask;
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}
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return 0xff;
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}
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void run_for_cycles(unsigned int number_of_cycles)
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{
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_interval_timer[0] -= number_of_cycles;
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_interval_timer[1] -= number_of_cycles;
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if(!_interval_timer[1] && _timer_is_running[1])
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{
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_timer_is_running[1] = false;
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_interrupt_flags |= InterruptFlag::Timer2;
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reevaluate_interrupts();
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}
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if(!_interval_timer[0] && _timer_is_running[0])
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{
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_interrupt_flags |= InterruptFlag::Timer1;
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reevaluate_interrupts();
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// TODO: reload shouldn't occur for a further 1.5 cycles
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if(_auxiliary_control_register&0x40)
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{
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_interval_timer[0] = _interval_timer_latch[0];
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}
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else
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_timer_is_running[0] = false;
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}
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// TODO: lots of other status effects
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}
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bool get_interrupt_line()
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{
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uint8_t interrupt_status = _interrupt_flags & (~_interrupt_mask) & 0x7f;
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return !!interrupt_status;
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}
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private:
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inline void reevaluate_interrupts()
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{
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if(_delegate) _delegate->mos6522_did_change_interrupt_status(this);
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}
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MOS6522Delegate *_delegate;
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uint16_t _interval_timer[2], _interval_timer_latch[2];
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uint8_t _shift_register;
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uint8_t _input_latch[2];
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uint8_t _data_direction[2];
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uint8_t _interrupt_flags, _interrupt_mask;
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bool _timer_is_running[2];
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uint8_t _interrupt_flag_register, _interrupt_enable_register;
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uint8_t _peripheral_control_register, _auxiliary_control_register;
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};
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}
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#endif /* _522_hpp */
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