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Edges towards working counters.

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This commit is contained in:
Thomas Harte 2021-07-23 22:43:47 -04:00
parent c733a4dbf8
commit 77a8ddb95c
2 changed files with 76 additions and 19 deletions
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65
Components/6526/Implementation/6526Implementation.hpp
View File

@ -68,10 +68,10 @@ void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
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;
case 4: counter_[0].reload = (counter_[0].reload & 0xff00) | uint16_t(value << 0); break;
case 5: counter_[0].reload = (counter_[0].reload & 0x00ff) | uint16_t(value << 8); break;
case 6: counter_[1].reload = (counter_[1].reload & 0xff00) | uint16_t(value << 0); break;
case 7: counter_[1].reload = (counter_[1].reload & 0x00ff) | uint16_t(value << 8); break;
// Time-of-day clock.
//
@ -79,7 +79,7 @@ void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
// upon a write to the LSB.
case 8:
if constexpr (personality == Personality::P8250) {
if(control_[1] & 0x80) {
if(counter_[1].control & 0x80) {
tod_alarm_ = (tod_alarm_ & 0xffff00) | uint32_t(value);
} else {
tod_ = (tod_ & 0xffff00) | uint32_t(value);
@ -92,7 +92,7 @@ void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
break;
case 9:
if constexpr (personality == Personality::P8250) {
if(control_[1] & 0x80) {
if(counter_[1].control & 0x80) {
tod_alarm_ = (tod_alarm_ & 0xff00ff) | uint32_t(value << 8);
} else {
tod_ = (tod_ & 0xff00ff) | uint32_t(value << 8);
@ -105,7 +105,7 @@ void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
break;
case 10:
if constexpr (personality == Personality::P8250) {
if(control_[1] & 0x80) {
if(counter_[1].control & 0x80) {
tod_alarm_ = (tod_alarm_ & 0x00ffff) | uint32_t(value << 16);
} else {
tod_ = (tod_ & 0x00ffff) | uint32_t(value << 16);
@ -136,9 +136,19 @@ void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
// Control.
case 14:
if(value & 0x10) {
counter_[0].value = counter_[0].reload;
}
counter_[0].control = value & 0xef;
printf("Ignoring control A write: %02x\n", value);
break;
case 15:
control_[address - 14] = value;
printf("Ignoring control write: %02x to %d\n", value, address);
if(value & 0x10) {
counter_[1].value = counter_[1].reload;
}
counter_[1].control = value;
printf("Ignoring control B write: %02x\n", value);
break;
default:
@ -159,10 +169,10 @@ uint8_t MOS6526<BusHandlerT, personality>::read(int address) {
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 4: return uint8_t(counter_[0].value >> 0);
case 5: return uint8_t(counter_[0].value >> 8);
case 6: return uint8_t(counter_[1].value >> 0);
case 7: return uint8_t(counter_[1].value >> 0);
// Interrupt state.
case 13: {
@ -173,7 +183,7 @@ uint8_t MOS6526<BusHandlerT, personality>::read(int address) {
} break;
case 14: case 15:
return control_[address - 14];
return counter_[address - 14].control;
// Time-of-day clock.
//
@ -237,8 +247,31 @@ void MOS6526<BusHandlerT, personality>::run_for(const HalfCycles 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;
// Is counter A running and linked to the clock input?
int counter_a_underflows = 0;
if((counter_[0].control & 0x21) == 0x01) {
counter_a_underflows = counter_[0].subtract(sub);
}
// Update counter B.
int counter_b_underflows = 0;
switch(counter_[1].control & 0x61) {
case 0x01:
counter_b_underflows = counter_[1].subtract(sub);
break;
case 0x41:
counter_b_underflows = counter_[1].subtract(counter_a_underflows);
break;
default:
if(counter_[1].control & 1) {
printf("Unimplemented 6526 CNT input\n");
assert(false);
}
break;
}
// Apply interrupts.
posit_interrupt((counter_a_underflows ? 0x01 : 0x00) | (counter_b_underflows ? 0x02 : 0x00));
}
template <typename BusHandlerT, Personality personality>

30
Components/6526/Implementation/6526Storage.hpp
View File

@ -21,8 +21,6 @@ struct MOS6526Storage {
uint8_t interrupt_control_ = 0;
uint8_t interrupt_state_ = 0;
uint8_t control_[2] = {0, 0};
uint32_t tod_increment_mask_ = uint32_t(~0);
uint32_t tod_latch_ = 0;
uint32_t tod_ = 0;
@ -31,7 +29,33 @@ struct MOS6526Storage {
struct Counter {
uint16_t reload = 0;
uint16_t value = 0;
} counters_[2];
uint8_t control = 0;
// int one_shot_mask = 0;
int subtract(int count) {
if(control & 8) {
// One-shot.
// value -= count;
// if(value < 0) {
// const int underflows = one_shot_mask;
// value = 0;
// one_shot_mask = 0;
// return underflows;
// }
return 0;
} else {
// Continuous.
value -= count;
value -= (reload + 1);
const int underflows = -value / (reload + 1);
value %= (reload + 1);
value += (reload + 1);
return underflows;
}
}
} counter_[2];
};
}