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Implements time-of-day counters, provisionally.

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Interrupts to do.
This commit is contained in:
Thomas Harte
2021-07-23 21:24:07 -04:00
parent 6216d53b1a
commit d898a43dff
6 changed files with 170 additions and 25 deletions
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Components/6526/Implementation/6526Implementation.hpp
+131 -14
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@@ -17,14 +17,14 @@ namespace MOS6526 {
template <typename BusHandlerT, Personality personality>
template <int port> void MOS6526<BusHandlerT, personality>::set_port_output() {
const uint8_t output = registers_.output[port] | (~registers_.data_direction[port]);
const uint8_t output = output_[port] | (~data_direction_[port]);
port_handler_.set_port_output(Port(port), output);
}
template <typename BusHandlerT, Personality personality>
template <int port> uint8_t MOS6526<BusHandlerT, personality>::get_port_input() {
const uint8_t input = port_handler_.get_port_input(Port(port));
return (input & ~registers_.data_direction[port]) | (registers_.output[port] & registers_.data_direction[port]);
return (input & ~data_direction_[port]) | (output_[port] & data_direction_[port]);
}
template <typename BusHandlerT, Personality personality>
@@ -37,40 +37,85 @@ void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
switch(address) {
// Port output.
case 0:
registers_.output[0] = value;
output_[0] = value;
set_port_output<0>();
break;
case 1:
registers_.output[1] = value;
output_[1] = value;
set_port_output<1>();
break;
// Port direction.
case 2:
registers_.data_direction[0] = value;
data_direction_[0] = value;
set_port_output<0>();
break;
case 3:
registers_.data_direction[1] = value;
data_direction_[1] = value;
set_port_output<1>();
break;
// Counters; writes set the reload values.
case 4: counters_[0].reload = (counters_[0].reload & 0xff00) | uint16_t(value << 0); break;
case 5: counters_[0].reload = (counters_[0].reload & 0x00ff) | uint16_t(value << 8); break;
case 6: counters_[1].reload = (counters_[1].reload & 0xff00) | uint16_t(value << 0); break;
case 7: counters_[1].reload = (counters_[1].reload & 0x00ff) | uint16_t(value << 8); break;
// Time-of-day clock.
//
// 8520: a binary counter; stopped on any write, restarted
// upon a write to the LSB.
case 8:
if constexpr (personality == Personality::P8250) {
tod_ = (tod_ & 0xffff00) | uint32_t(value);
tod_increment_mask_ = uint32_t(~0);
} else {
printf("6526 TOD clock not implemented\n");
assert(false);
}
break;
case 9:
if constexpr (personality == Personality::P8250) {
tod_ = (tod_ & 0xff00ff) | uint32_t(value << 8);
tod_increment_mask_ = 0;
} else {
printf("6526 TOD clock not implemented\n");
assert(false);
}
break;
case 10:
if constexpr (personality == Personality::P8250) {
tod_ = (tod_ & 0x00ffff) | uint32_t(value << 16);
tod_increment_mask_ = 0;
} else {
printf("6526 TOD clock not implemented\n");
assert(false);
}
break;
case 11:
if constexpr (personality != Personality::P8250) {
printf("6526 TOD clock not implemented\n");
assert(false);
}
break;
// Interrupt control.
case 13:
registers_.interrupt_control_ = value;
interrupt_control_ = value;
update_interrupts();
break;
// Control.
case 14:
case 15:
registers_.control[address - 14] = value;
control_[address - 14] = value;
printf("Ignoring control write: %02x to %d\n", value, address);
break;
default:
printf("Unhandled 6526 write: %02x to %d\n", value, address);
// assert(false);
assert(false);
break;
}
}
@@ -81,17 +126,72 @@ uint8_t MOS6526<BusHandlerT, personality>::read(int address) {
switch(address) {
case 0: return get_port_input<0>();
case 1: return get_port_input<1>();
case 13: return registers_.interrupt_control_;
case 13: return interrupt_control_;
case 2: case 3:
return registers_.data_direction[address - 2];
return data_direction_[address - 2];
// Counters; reads obtain the current values.
case 4: return uint8_t(counters_[0].value >> 0);
case 5: return uint8_t(counters_[0].value >> 8);
case 6: return uint8_t(counters_[1].value >> 0);
case 7: return uint8_t(counters_[1].value >> 0);
case 14: case 15:
return registers_.control[address - 14];
return control_[address - 14];
// Time-of-day clock.
//
// 8250: Latch on MSB. Unlatch on LSB. Read raw if not latched.
case 8:
if constexpr (personality == Personality::P8250) {
if(tod_latch_) {
const uint8_t result = tod_latch_ & 0xff;
tod_latch_ = 0;
return result;
} else {
return tod_ & 0xff;
}
} else {
printf("6526 TOD clock not implemented\n");
assert(false);
}
break;
case 9:
if constexpr (personality == Personality::P8250) {
if(tod_latch_) {
return (tod_latch_ >> 8) & 0xff;
} else {
return (tod_ >> 8) & 0xff;
}
} else {
printf("6526 TOD clock not implemented\n");
assert(false);
}
break;
case 10:
if constexpr (personality == Personality::P8250) {
tod_latch_ = tod_ | 0xff00'0000;
return (tod_ >> 16) & 0xff;
} else {
printf("6526 TOD clock not implemented\n");
assert(false);
}
break;
case 11:
if constexpr (personality == Personality::P8250) {
return 0x00; // Assumed. Just a guss.
} else {
printf("6526 TOD clock not implemented\n");
assert(false);
}
break;
default:
printf("Unhandled 6526 read from %d\n", address);
// assert(false);
assert(false);
break;
}
return 0xff;
@@ -99,9 +199,26 @@ uint8_t MOS6526<BusHandlerT, personality>::read(int address) {
template <typename BusHandlerT, Personality personality>
void MOS6526<BusHandlerT, personality>::run_for(const HalfCycles half_cycles) {
(void)half_cycles;
half_divider_ += half_cycles;
const int sub = half_divider_.divide_cycles().template as<int>();
// TODO: apply to timers, depending on mode.
(void)sub;
}
template <typename BusHandlerT, Personality personality>
void MOS6526<BusHandlerT, personality>::advance_tod(int count) {
if constexpr(personality == Personality::P8250) {
// The 8250 uses a simple binary counter to replace the
// 6526's time-of-day clock. So this is easy.
tod_ += uint32_t(count) & tod_increment_mask_;
} else {
// The 6526 uses a time-of-day clock. This may or may not
// be accurate.
}
}
}
}