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324 lines
8.1 KiB
C++
324 lines
8.1 KiB
C++
//
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// RP5C01.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 14/01/2023.
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// Copyright © 2023 Thomas Harte. All rights reserved.
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//
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#include "RP5C01.hpp"
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#include "../../Numeric/NumericCoder.hpp"
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#include <ctime>
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using namespace Ricoh::RP5C01;
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RP5C01::RP5C01(HalfCycles clock_rate) : clock_rate_(clock_rate) {
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// Seed internal clock.
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std::time_t now = std::time(NULL);
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std::tm *time_date = std::localtime(&now);
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seconds_ =
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time_date->tm_sec +
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time_date->tm_min * 60 +
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time_date->tm_hour * 60 * 60;
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day_of_the_week_ = time_date->tm_wday;
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day_ = time_date->tm_mday;
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month_ = time_date->tm_mon;
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year_ = (time_date->tm_year + 20) % 100; // This is probably MSX specific; rethink if/when other machines use this chip.
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leap_year_ = time_date->tm_year % 4;
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}
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void RP5C01::run_for(HalfCycles cycles) {
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sub_seconds_ += cycles;
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// Guess: this happens so rarely (i.e. once a second, ordinarily) that
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// it's not worth worrying about the branch prediction consequences.
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//
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// ... and ditto all the conditionals below, which will be very rarely reached.
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if(sub_seconds_ < clock_rate_) {
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return;
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}
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const auto elapsed_seconds = int(sub_seconds_.as_integral() / clock_rate_.as_integral());
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sub_seconds_ %= clock_rate_;
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// Update time within day.
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seconds_ += elapsed_seconds;
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constexpr int day_length = 60 * 60 * 24;
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if(seconds_ < day_length) {
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return;
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}
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const int elapsed_days = seconds_ / day_length;
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seconds_ %= day_length;
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// Day of the week doesn't aggregate upwards.
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day_of_the_week_ = (day_of_the_week_ + elapsed_days) % 7;
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// Assumed for now: day and month run from 0.
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// A leap year count of 0 implies a leap year.
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// TODO: verify.
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day_ += elapsed_days;
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while(true) {
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int month_length = 1;
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switch(month_) {
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default:
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case 0: month_length = 31; break;
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case 1: month_length = 28 + !leap_year_; break;
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case 2: month_length = 31; break;
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case 3: month_length = 30; break;
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case 4: month_length = 31; break;
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case 5: month_length = 30; break;
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case 6: month_length = 31; break;
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case 7: month_length = 31; break;
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case 8: month_length = 30; break;
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case 9: month_length = 31; break;
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case 10: month_length = 30; break;
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case 11: month_length = 31; break;
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}
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if(day_ < month_length) {
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return;
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}
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day_ -= month_length;
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++month_;
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if(month_ == 12) {
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month_ = 0;
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year_ = (year_ + 1) % 100;
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leap_year_ = (leap_year_ + 1) & 3;
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}
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}
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}
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namespace {
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constexpr int Reg(int mode, int address) {
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return address | mode << 4;
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}
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constexpr int PM = 1 << 4;
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constexpr int twenty_four_to_twelve(int hours) {
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switch(hours) {
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default: return (hours % 12) + (hours > 12 ? PM : 0);
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case 0: return 12;
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case 12: return 12 | PM;
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}
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}
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constexpr int twelve_to_twenty_four(int hours) {
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hours = (hours & 0xf) + (hours & PM ? 12 : 0);
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switch(hours) {
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default: break;
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case 24: return 12;
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case 12: return 0;
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}
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return hours;
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}
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using SecondEncoder = Numeric::NumericCoder<
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10, 6, // Seconds.
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10, 6, // Minutes.
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24 // Hours
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>;
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using TwoDigitEncoder = Numeric::NumericCoder<10, 10>;
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}
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/// Performs a write of @c value to @c address.
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void RP5C01::write(int address, uint8_t value) {
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address &= 0xf;
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value &= 0xf;
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// Handle potential RAM accesses.
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if(address < 0xd && mode_ >= 2) {
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address += mode_ == 3 ? 13 : 0;
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ram_[size_t(address)] = value & 0xf;
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return;
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}
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switch(Reg(mode_, address)) {
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default: break;
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// Seconds.
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case Reg(0, 0x00): SecondEncoder::encode<0>(seconds_, value); break;
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case Reg(0, 0x01): SecondEncoder::encode<1>(seconds_, value); break;
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// Minutes.
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case Reg(0, 0x02): SecondEncoder::encode<2>(seconds_, value); break;
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case Reg(0, 0x03): SecondEncoder::encode<3>(seconds_, value); break;
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// Hours.
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case Reg(0, 0x04):
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case Reg(0, 0x05): {
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int hours = SecondEncoder::decode<4>(seconds_);
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if(!twentyfour_hour_clock_) {
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hours = twenty_four_to_twelve(hours);
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}
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if(address == 0x4) {
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TwoDigitEncoder::encode<0>(hours, value);
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} else {
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TwoDigitEncoder::encode<1>(hours, value & 3);
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}
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if(!twentyfour_hour_clock_) {
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hours = twelve_to_twenty_four(hours);
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}
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SecondEncoder::encode<4>(seconds_, hours);
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} break;
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// Day of the week.
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case Reg(0, 0x06): day_of_the_week_ = value % 7; break;
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// Day.
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case Reg(0, 0x07): TwoDigitEncoder::encode<0>(day_, value); break;
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case Reg(0, 0x08): TwoDigitEncoder::encode<1>(day_, value & 3); break;
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// Month.
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case Reg(0, 0x09): TwoDigitEncoder::encode<0>(month_, (value - 1)); break;
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case Reg(0, 0x0a): TwoDigitEncoder::encode<1>(month_, (value - 1) & 1); break;
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// Year.
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case Reg(0, 0x0b): TwoDigitEncoder::encode<0>(year_, value); break;
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case Reg(0, 0x0c): TwoDigitEncoder::encode<1>(year_, value); break;
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// TODO: alarm minutes.
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case Reg(1, 0x02):
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case Reg(1, 0x03): break;
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// TODO: alarm hours.
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case Reg(1, 0x04):
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case Reg(1, 0x05): break;
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// TODO: alarm day-of-the-week.
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case Reg(1, 0x06): break;
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// TODO: alarm day.
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case Reg(1, 0x07):
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case Reg(1, 0x08): break;
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// 24/12-hour clock.
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case Reg(1, 0x0a):
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twentyfour_hour_clock_ = value & 1;
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break;
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// Lead-year counter.
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case Reg(1, 0x0b):
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leap_year_ = value & 3;
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break;
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//
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// Registers D–F don't depend on the mode.
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//
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case Reg(0, 0xd): case Reg(1, 0xd): case Reg(2, 0xd): case Reg(3, 0xd):
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timer_enabled_ = value & 0x8;
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alarm_enabled_ = value & 0x4;
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mode_ = value & 0x3;
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break;
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case Reg(0, 0xe): case Reg(1, 0xe): case Reg(2, 0xe): case Reg(3, 0xe):
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// Test register; unclear what is supposed to happen.
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break;
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case Reg(0, 0xf): case Reg(1, 0xf): case Reg(2, 0xf): case Reg(3, 0xf):
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one_hz_on_ = !(value & 0x8);
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sixteen_hz_on_ = !(value & 0x4);
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// TODO: b0 = alarm reset; b1 = timer reset.
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break;
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}
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}
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uint8_t RP5C01::read(int address) {
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address &= 0xf;
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if(address < 0xd && mode_ >= 2) {
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address += mode_ == 3 ? 13 : 0;
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return 0xf0 | ram_[size_t(address)];
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}
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int value = 0xf;
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switch(Reg(mode_, address)) {
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// Second.
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case Reg(0, 0x00): value = SecondEncoder::decode<0>(seconds_); break;
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case Reg(0, 0x01): value = SecondEncoder::decode<1>(seconds_); break;
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// Minute.
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case Reg(0, 0x02): value = SecondEncoder::decode<2>(seconds_); break;
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case Reg(0, 0x03): value = SecondEncoder::decode<3>(seconds_); break;
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// Hour.
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case Reg(0, 0x04):
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case Reg(0, 0x05): {
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int hours = SecondEncoder::decode<4>(seconds_);
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if(!twentyfour_hour_clock_) {
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hours = twenty_four_to_twelve(hours);
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}
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if(address == 0x4) {
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value = TwoDigitEncoder::decode<0>(hours);
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} else {
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value = TwoDigitEncoder::decode<1>(hours);
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}
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} break;
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// Day-of-the-week.
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case Reg(0, 0x06): value = day_of_the_week_; break;
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// Day.
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case Reg(0, 0x07): value = TwoDigitEncoder::decode<0>(day_); break;
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case Reg(0, 0x08): value = TwoDigitEncoder::decode<1>(day_); break;
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// Month.
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case Reg(0, 0x09): value = TwoDigitEncoder::decode<0>(month_ + 1); break;
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case Reg(0, 0x0a): value = TwoDigitEncoder::decode<1>(month_ + 1); break;
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// Year.
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case Reg(0, 0x0b): value = TwoDigitEncoder::decode<0>(year_); break;
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case Reg(0, 0x0c): value = TwoDigitEncoder::decode<1>(year_); break;
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// TODO: alarm minutes.
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case Reg(1, 0x02):
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case Reg(1, 0x03): break;
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// TODO: alarm hours.
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case Reg(1, 0x04):
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case Reg(1, 0x05): break;
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// TODO: alarm day-of-the-week.
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case Reg(1, 0x06): break;
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// TODO: alarm day.
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case Reg(1, 0x07):
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case Reg(1, 0x08): break;
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// 12/24-hour clock.
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case Reg(1, 0x0a): value = twentyfour_hour_clock_; break;
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// Leap year.
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case Reg(1, 0x0b): value = leap_year_; break;
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//
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// Registers D–F don't depend on the mode.
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//
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case Reg(0, 0xd): case Reg(1, 0xd): case Reg(2, 0xd): case Reg(3, 0xd):
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value =
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(timer_enabled_ ? 0x8 : 0x0) |
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(alarm_enabled_ ? 0x4 : 0x0) |
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mode_;
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break;
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case Reg(0, 0xe): case Reg(1, 0xe): case Reg(2, 0xe): case Reg(3, 0xe):
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// Test register; unclear what is supposed to happen.
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break;
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case Reg(0, 0xf): case Reg(1, 0xf): case Reg(2, 0xf): case Reg(3, 0xf):
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value =
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(one_hz_on_ ? 0x0 : 0x8) |
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(sixteen_hz_on_ ? 0x0 : 0x4);
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break;
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}
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return uint8_t(0xf0 | value);
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}
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