mirror of
https://github.com/TomHarte/CLK.git
synced 2024-09-06 20:54:31 +00:00
101 lines
2.4 KiB
C++
101 lines
2.4 KiB
C++
//
|
||
// RP5C01.cpp
|
||
// Clock Signal
|
||
//
|
||
// Created by Thomas Harte on 14/01/2023.
|
||
// Copyright © 2023 Thomas Harte. All rights reserved.
|
||
//
|
||
|
||
#include "RP5C01.hpp"
|
||
|
||
using namespace Ricoh::RP5C01;
|
||
|
||
RP5C01::RP5C01(HalfCycles clock_rate) : clock_rate_(clock_rate) {}
|
||
|
||
void RP5C01::run_for(HalfCycles cycles) {
|
||
sub_seconds_ += cycles;
|
||
|
||
// Guess: this happens so rarely (i.e. once a second, ordinarily) that
|
||
// it's not worth worrying about the branch prediction consequences.
|
||
//
|
||
// ... and ditto all the conditionals below, which will be very rarely reached.
|
||
if(sub_seconds_ < clock_rate_) {
|
||
return;
|
||
}
|
||
const auto elapsed_seconds = int(sub_seconds_.as_integral() / clock_rate_.as_integral());
|
||
sub_seconds_ %= clock_rate_;
|
||
|
||
// Update time within day.
|
||
seconds_ += elapsed_seconds;
|
||
|
||
constexpr int day_length = 60 * 60 * 24;
|
||
if(seconds_ < day_length) {
|
||
return;
|
||
}
|
||
const int elapsed_days = seconds_ / day_length;
|
||
seconds_ %= day_length;
|
||
|
||
// Day of the week doesn't aggregate upwards.
|
||
day_of_the_week_ = (day_of_the_week_ + elapsed_days) % 7;
|
||
|
||
// Assumed for now: day and month run from 0.
|
||
// A leap year count of 0 implies a leap year.
|
||
// TODO: verify.
|
||
day_ += elapsed_days;
|
||
while(true) {
|
||
int month_length = 1;
|
||
switch(month_) {
|
||
case 0: month_length = 31; break;
|
||
case 1: month_length = 28 + !leap_year_; break;
|
||
case 2: month_length = 31; break;
|
||
case 3: month_length = 30; break;
|
||
case 4: month_length = 31; break;
|
||
case 5: month_length = 30; break;
|
||
case 6: month_length = 31; break;
|
||
case 7: month_length = 31; break;
|
||
case 8: month_length = 30; break;
|
||
case 9: month_length = 31; break;
|
||
case 10: month_length = 30; break;
|
||
case 11: month_length = 31; break;
|
||
}
|
||
|
||
if(day_ < month_length) {
|
||
return;
|
||
}
|
||
|
||
day_ -= month_length;
|
||
++month_;
|
||
|
||
if(month_ == 12) {
|
||
month_ = 0;
|
||
++year_;
|
||
leap_year_ = (leap_year_ + 1) & 3;
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Performs a write of @c value to @c address.
|
||
void RP5C01::write(int address, uint8_t value) {
|
||
// Registers D–F don't depend on the mode.
|
||
if(address >= 0xd) {
|
||
switch(address) {
|
||
default: break;
|
||
case 0xd:
|
||
timer_enabled_ = value & 0x8;
|
||
alarm_enabled_ = value & 0x4;
|
||
mode_ = value & 0x3;
|
||
break;
|
||
case 0xe:
|
||
// Test register; unclear what is supposed to happen.
|
||
break;
|
||
case 0xf:
|
||
one_hz_on_ = !(value & 0x8);
|
||
sixteen_hz_on_ = !(value & 0x4);
|
||
// TODO: timer reset on bit 1, alarm reset on bit 0
|
||
break;
|
||
}
|
||
|
||
return;
|
||
}
|
||
}
|