Start sketching out an RP5C01.

Components/RP5C01/RP5C01.cpp

@@ -0,0 +1,100 @@
+//
+//  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;
+	}
+}

Components/RP5C01/RP5C01.hpp

@@ -0,0 +1,62 @@
+//
+//  RP5C01.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 14/01/2023.
+//  Copyright © 2023 Thomas Harte. All rights reserved.
+//
+
+#ifndef RP5C01_hpp
+#define RP5C01_hpp
+
+#include "../../ClockReceiver/ClockReceiver.hpp"
+
+#include <array>
+#include <cstdint>
+
+namespace Ricoh {
+namespace RP5C01 {
+
+class RP5C01 {
+	public:
+		RP5C01(HalfCycles clock_rate);
+
+		/// @returns the result of a read from @c address.
+		uint8_t read(int address);
+
+		/// Performs a write of @c value to @c address.
+		void write(int address, uint8_t value);
+
+		/// Advances time.
+		void run_for(HalfCycles);
+
+	private:
+		std::array<uint8_t, 26> ram_;
+
+		HalfCycles sub_seconds_;
+		const HalfCycles clock_rate_;
+
+		// Contains the seconds, minutes and hours fields.
+		int seconds_ = 0;
+
+		// Calendar entries.
+		int day_of_the_week_ = 0;
+		int day_ = 0;
+		int month_ = 0;
+		int year_ = 1988;
+		int leap_year_ = 0;
+
+		// Other flags.
+		bool timer_enabled_ = false;
+		bool alarm_enabled_ = false;
+		int mode_ = 0;
+		bool one_hz_on_ = false;
+		bool sixteen_hz_on_ = false;
+};
+
+}
+}
+
+#include <stdio.h>
+
+#endif /* RP5C01_hpp */

OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj

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+		4BF0BC702973318E00CCA2B5 /* RP5C01.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = RP5C01.hpp; sourceTree = "<group>"; };
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@@ -4579,6 +4583,7 @@
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 				4B4B1A39200198C900A0F866 /* KonamiSCC */,
 				4BC23A212467600E001A6030 /* OPx */,
+				4BF0BC6E2973318E00CCA2B5 /* RP5C01 */,
 				4B0ACBFF237756EC008902D0 /* Serial */,
 				4BB0A6582044FD3000FB3688 /* SN76489 */,
 			);
@@ -4948,6 +4953,15 @@
 			path = Formats;
 			sourceTree = "<group>";
 		};
+		4BF0BC6E2973318E00CCA2B5 /* RP5C01 */ = {
+			isa = PBXGroup;
+			children = (
+				4BF0BC6F2973318E00CCA2B5 /* RP5C01.cpp */,
+				4BF0BC702973318E00CCA2B5 /* RP5C01.hpp */,
+			);
+			path = RP5C01;
+			sourceTree = "<group>";
+		};
 		4BF660691F281573002CB053 /* ClockReceiver */ = {
 			isa = PBXGroup;
 			children = (
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 				4B894519201967B4007DE474 /* ConfidenceCounter.cpp in Sources */,
 				4B055AEE1FAE9BBF0060FFFF /* Keyboard.cpp in Sources */,
+				4BF0BC722973318E00CCA2B5 /* RP5C01.cpp in Sources */,
 				4B055AED1FAE9BA20060FFFF /* Z80Storage.cpp in Sources */,
 				4B1B88BC202E2EC100B67DFF /* MultiKeyboardMachine.cpp in Sources */,
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 				4B8DD3862634D37E00B3C866 /* SNA.cpp in Sources */,
 				4B4DEC06252BFA56004583AC /* 65816Base.cpp in Sources */,
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