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211 lines
5.1 KiB
C++
211 lines
5.1 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_register(int address, uint8_t value)
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{
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address &= 0xf;
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switch(address)
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{
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case 0x00:
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_registers.output[1] = value;
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break;
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case 0x01:
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_registers.output[0] = value;
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break;
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case 0xf:
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_registers.output[0] = value;
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break;
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case 0x02:
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_registers.data_direction[1] = value;
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break;
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case 0x03:
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_registers.data_direction[0] = value;
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break;
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// Timer 1
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case 0x06: case 0x04: _registers.timer_latch[0] = (_registers.timer_latch[0]&0xff00) | value; break;
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case 0x05: case 0x07:
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_registers.timer_latch[0] = (_registers.timer_latch[0]&0x00ff) | (uint16_t)(value << 8);
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_registers.interrupt_flags &= ~InterruptFlag::Timer1;
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if(address == 0x05)
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{
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_registers.timer[0] = _registers.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: _registers.timer_latch[1] = value; break;
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case 0x09:
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_registers.interrupt_flags &= ~InterruptFlag::Timer2;
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_registers.timer[1] = _registers.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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// Shift
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case 0xa: _registers.shift = value; break;
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// Control
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case 0xb: _registers.auxiliary_control = value; break;
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case 0xc: _registers.peripheral_control = value; break;
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// Interrupt control
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case 0xd:
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_registers.interrupt_flags = value; // TODO: really?
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reevaluate_interrupts();
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break;
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case 0xe:
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if(value&0x80) value = ~value;
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_registers.interrupt_enable = value;
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reevaluate_interrupts();
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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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address &= 0xf;
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switch(address)
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{
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case 0x00: return _registers.input[1];
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case 0x01: return _registers.input[0];
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case 0x02: return _registers.data_direction[1];
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case 0x03: return _registers.data_direction[0];
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case 0x0f: return _registers.input[1];
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// Timer 1
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case 0x04:
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_registers.interrupt_flags &= ~InterruptFlag::Timer1;
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reevaluate_interrupts();
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return _registers.timer[0] & 0x00ff;
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case 0x05: return _registers.timer[0] >> 8;
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case 0x06: return _registers.timer_latch[0] & 0x00ff;
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case 0x07: return _registers.timer_latch[0] >> 8;
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// Timer 2
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case 0x08:
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_registers.interrupt_flags &= ~InterruptFlag::Timer2;
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reevaluate_interrupts();
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return _registers.timer[1] & 0x00ff;
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case 0x09: return _registers.timer[1] >> 8;
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case 0x0a: return _registers.shift;
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case 0x0b: return _registers.auxiliary_control;
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case 0x0c: return _registers.peripheral_control;
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case 0x0d: return _registers.interrupt_flags | (get_interrupt_line() ? 0x80 : 0x00);
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case 0x0e: return ~_registers.interrupt_enable;
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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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_registers.timer[0] -= number_of_cycles;
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_registers.timer[1] -= number_of_cycles;
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if(!_registers.timer[1] && _timer_is_running[1])
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{
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_timer_is_running[1] = false;
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_registers.interrupt_flags |= InterruptFlag::Timer2;
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reevaluate_interrupts();
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}
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if(!_registers.timer[0] && _timer_is_running[0])
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{
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_registers.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(_registers.auxiliary_control&0x40)
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{
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_registers.timer[0] = _registers.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 = _registers.interrupt_flags & _registers.interrupt_enable & 0x7f;
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return !!interrupt_status;
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}
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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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_timer_is_running{false, false},
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_last_posted_interrupt_status(false)
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{}
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private:
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bool _last_posted_interrupt_status;
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inline void reevaluate_interrupts()
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{
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bool new_interrupt_status = get_interrupt_line();
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if(new_interrupt_status != _last_posted_interrupt_status)
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{
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_last_posted_interrupt_status = new_interrupt_status;
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if(_delegate) _delegate->mos6522_did_change_interrupt_status(this);
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}
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}
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MOS6522Delegate *_delegate;
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struct Registers {
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uint8_t output[2], input[2], data_direction[2];
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uint16_t timer[2], timer_latch[2];
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uint8_t shift;
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uint8_t auxiliary_control, peripheral_control;
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uint8_t interrupt_flags, interrupt_enable;
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Registers() : data_direction{0, 0} {}
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} _registers;
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bool _timer_is_running[2];
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};
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}
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#endif /* _522_hpp */
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