mirror of
https://github.com/TomHarte/CLK.git
synced 2024-11-26 23:52:26 +00:00
117 lines
3.2 KiB
C++
117 lines
3.2 KiB
C++
//
|
|
// 6522Base.cpp
|
|
// Clock Signal
|
|
//
|
|
// Created by Thomas Harte on 04/09/2017.
|
|
// Copyright © 2017 Thomas Harte. All rights reserved.
|
|
//
|
|
|
|
#include "../6522.hpp"
|
|
|
|
using namespace MOS::MOS6522;
|
|
|
|
void MOS6522Base::set_control_line_input(Port port, Line line, bool value) {
|
|
switch(line) {
|
|
case Line::One:
|
|
if( value != control_inputs_[port].line_one &&
|
|
value == !!(registers_.peripheral_control & (port ? 0x10 : 0x01))
|
|
) {
|
|
registers_.interrupt_flags |= port ? InterruptFlag::CB1ActiveEdge : InterruptFlag::CA1ActiveEdge;
|
|
reevaluate_interrupts();
|
|
}
|
|
control_inputs_[port].line_one = value;
|
|
break;
|
|
|
|
case Line::Two:
|
|
// TODO: output modes, but probably elsewhere?
|
|
if( value != control_inputs_[port].line_two && // i.e. value has changed ...
|
|
!(registers_.peripheral_control & (port ? 0x80 : 0x08)) && // ... and line is input ...
|
|
value == !!(registers_.peripheral_control & (port ? 0x40 : 0x04)) // ... and it's either high or low, as required
|
|
) {
|
|
registers_.interrupt_flags |= port ? InterruptFlag::CB2ActiveEdge : InterruptFlag::CA2ActiveEdge;
|
|
reevaluate_interrupts();
|
|
}
|
|
control_inputs_[port].line_two = value;
|
|
break;
|
|
}
|
|
}
|
|
|
|
void MOS6522Base::do_phase2() {
|
|
registers_.last_timer[0] = registers_.timer[0];
|
|
registers_.last_timer[1] = registers_.timer[1];
|
|
|
|
if(registers_.timer_needs_reload) {
|
|
registers_.timer_needs_reload = false;
|
|
registers_.timer[0] = registers_.timer_latch[0];
|
|
} else {
|
|
registers_.timer[0] --;
|
|
}
|
|
|
|
registers_.timer[1] --;
|
|
if(registers_.next_timer[0] >= 0) {
|
|
registers_.timer[0] = static_cast<uint16_t>(registers_.next_timer[0]);
|
|
registers_.next_timer[0] = -1;
|
|
}
|
|
if(registers_.next_timer[1] >= 0) {
|
|
registers_.timer[1] = static_cast<uint16_t>(registers_.next_timer[1]);
|
|
registers_.next_timer[1] = -1;
|
|
}
|
|
}
|
|
|
|
void MOS6522Base::do_phase1() {
|
|
// IRQ is raised on the half cycle after overflow
|
|
if((registers_.timer[1] == 0xffff) && !registers_.last_timer[1] && timer_is_running_[1]) {
|
|
timer_is_running_[1] = false;
|
|
registers_.interrupt_flags |= InterruptFlag::Timer2;
|
|
reevaluate_interrupts();
|
|
}
|
|
|
|
if((registers_.timer[0] == 0xffff) && !registers_.last_timer[0] && timer_is_running_[0]) {
|
|
registers_.interrupt_flags |= InterruptFlag::Timer1;
|
|
reevaluate_interrupts();
|
|
|
|
if(registers_.auxiliary_control&0x40)
|
|
registers_.timer_needs_reload = true;
|
|
else
|
|
timer_is_running_[0] = false;
|
|
}
|
|
}
|
|
|
|
/*! Runs for a specified number of half cycles. */
|
|
void MOS6522Base::run_for(const HalfCycles half_cycles) {
|
|
int number_of_half_cycles = half_cycles.as_int();
|
|
|
|
if(is_phase2_) {
|
|
do_phase2();
|
|
number_of_half_cycles--;
|
|
}
|
|
|
|
while(number_of_half_cycles >= 2) {
|
|
do_phase1();
|
|
do_phase2();
|
|
number_of_half_cycles -= 2;
|
|
}
|
|
|
|
if(number_of_half_cycles) {
|
|
do_phase1();
|
|
is_phase2_ = true;
|
|
} else {
|
|
is_phase2_ = false;
|
|
}
|
|
}
|
|
|
|
/*! Runs for a specified number of cycles. */
|
|
void MOS6522Base::run_for(const Cycles cycles) {
|
|
int number_of_cycles = cycles.as_int();
|
|
while(number_of_cycles--) {
|
|
do_phase1();
|
|
do_phase2();
|
|
}
|
|
}
|
|
|
|
/*! @returns @c true if the IRQ line is currently active; @c false otherwise. */
|
|
bool MOS6522Base::get_interrupt_line() {
|
|
uint8_t interrupt_status = registers_.interrupt_flags & registers_.interrupt_enable & 0x7f;
|
|
return !!interrupt_status;
|
|
}
|