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Attempts the shift register.

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This commit is contained in:
Thomas Harte 2019-05-08 14:54:40 -04:00
parent f0f9722ca6
commit 2e7bc0b98a
2 changed files with 43 additions and 6 deletions
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2
Components/6522/6522.hpp
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@ -111,6 +111,8 @@ template <class T> class MOS6522: public MOS6522Storage {
private:
void do_phase1();
void do_phase2();
void shift_in();
void shift_out();
T &bus_handler_;
void access(int address);

47
Components/6522/Implementation/6522Implementation.hpp
View File

@ -91,7 +91,7 @@ template <typename T> void MOS6522<T>::set_register(int address, uint8_t value)
registers_.auxiliary_control = value;
break;
case 0xc: {
const auto old_peripheral_control = registers_.peripheral_control;
// const auto old_peripheral_control = registers_.peripheral_control;
registers_.peripheral_control = value;
int shift = 0;
@ -208,16 +208,26 @@ template <typename T> void MOS6522<T>::reevaluate_interrupts() {
template <typename T> void MOS6522<T>::set_control_line_input(Port port, Line line, bool value) {
switch(line) {
case Line::One:
if( value != control_inputs_[port].lines[line] &&
value == !!(registers_.peripheral_control & (port ? 0x10 : 0x01))
) {
if( value != control_inputs_[port].lines[line]) {
// In handshake mode, any transition on C[A/B]1 sets output high on C[A/B]2.
if(handshake_modes_[port] == HandshakeMode::Handshake) {
set_control_line_output(port, Line::Two, true);
}
registers_.interrupt_flags |= port ? InterruptFlag::CB1ActiveEdge : InterruptFlag::CA1ActiveEdge;
reevaluate_interrupts();
// Set the proper transition interrupt bit if enabled.
if(value == !!(registers_.peripheral_control & (port ? 0x10 : 0x01))) {
registers_.interrupt_flags |= port ? InterruptFlag::CB1ActiveEdge : InterruptFlag::CA1ActiveEdge;
reevaluate_interrupts();
}
// If this is a low-to-high transition, consider updating the shift register.
if(value) {
switch((registers_.auxiliary_control >> 2)&7) {
default: break;
case 3: shift_in(); break;
case 7: shift_out(); break;
}
}
}
control_inputs_[port].lines[line] = value;
break;
@ -269,6 +279,15 @@ template <typename T> void MOS6522<T>::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;
// If the shift register is shifting according to this timer, do a shift.
switch((registers_.auxiliary_control >> 2)&7) {
default: break;
case 1: shift_in(); break;
case 4: shift_out(); break;
case 5: shift_out(); break; // TODO: present a clock on CB1.
}
registers_.interrupt_flags |= InterruptFlag::Timer2;
reevaluate_interrupts();
}
@ -282,6 +301,13 @@ template <typename T> void MOS6522<T>::do_phase1() {
else
timer_is_running_[0] = false;
}
// If the shift register is shifting according to the input clock, do a shift.
switch((registers_.auxiliary_control >> 2)&7) {
default: break;
case 2: shift_in(); break;
case 6: shift_out(); break;
}
}
/*! Runs for a specified number of half cycles. */
@ -335,5 +361,14 @@ template <typename T> void MOS6522<T>::set_control_line_output(Port port, Line l
}
}
template <typename T> void MOS6522<T>::shift_in() {
registers_.shift = uint8_t((registers_.shift << 1) | (control_inputs_[1].lines[1] ? 1 : 0));
}
template <typename T> void MOS6522<T>::shift_out() {
set_control_line_output(Port::B, Line::Two, registers_.shift & 0x80);
registers_.shift <<= 1;
}
}
}