Hack in read-only versions of the main registers.

Machines/PCCompatible/RTC.hpp

@@ -9,6 +9,8 @@
 #ifndef RTC_h
 #define RTC_h
 
+#include <ctime>
+
 namespace PCCompatible {
 
 class RTC {
@@ -22,17 +24,68 @@ class RTC {
 					// NMI not yet supported.
 				break;
 				case 1:
-					// TODO.
+					write_register(value);
 				break;
 			}
 		}
 
 		uint8_t read() {
-			return 0x00;
+			std::time_t now = std::time(NULL);
+			std::tm *time_date = std::localtime(&now);
+
+			switch(selected_) {
+				default:
+				return 0xff;
+
+				case 0x00:	return bcd(time_date->tm_sec);			// Seconds [0-59]
+				case 0x01:	return 0;	// Seconds alarm
+				case 0x02:	return bcd(time_date->tm_min);			// Minutes [0-59]
+				case 0x03:	return 0;	// Minutes alarm
+				case 0x04:
+					// Hours [1-12 or 0-23]
+					if(statusB_ & 2) {
+						return bcd(time_date->tm_hour);
+					}
+					return bcd(1 + (time_date->tm_hour + 11)%12);
+				break;
+				case 0x05:	return 0;	// Hours alarm
+				case 0x06:	return bcd(time_date->tm_wday + 1);		// Day of the week [Sunday = 1]
+				case 0x07:	return bcd(time_date->tm_mon);			// Date of the Month [1-31]
+				case 0x08:	return bcd(time_date->tm_mon + 1);		// Month [1-12]
+				case 0x09:	return bcd(time_date->tm_year % 100);	// Year [0-99]
+				case 0x32:	return bcd(19 + time_date->tm_year / 100);	// Century
+
+				case 0x0a:	return statusA_;
+				case 0x0b:	return statusB_;
+			}
 		}
 
 	private:
 		int selected_;
+
+		uint8_t statusA_ = 0x00;
+		uint8_t statusB_ = 0x00;
+
+		template <typename IntT>
+		uint8_t bcd(IntT input) {
+			// If calendar is in binary format, don't convert.
+			if(statusB_ & 4) {
+				return uint8_t(input);
+			}
+
+			// Convert a one or two digit number to BCD.
+			return uint8_t(
+				(input % 10) +
+				((input / 10) * 16)
+			);
+		}
+
+		void write_register(uint8_t value) {
+			switch(selected_) {
+				default: break;
+				case 0x0a:	statusA_ = value;	break;
+			}
+		}
 };
 
 }