REAL-TIME CLOCK PLUS RAM(RTC) The MC146818AP is a real-time clock (RTC) and CMOS RAM chip manufactured by Motorola (now part of NXP Semiconductors). Below are the factual specifications, descriptions, and features from Ic-phoenix technical data files:
### **Manufacturer:**
Motorola (now NXP Semiconductors)
### **Specifications:**
- **Type:** Real-Time Clock (RTC) with CMOS RAM
- **Technology:** CMOS
- **Package:** 24-pin DIP (Dual In-line Package)
- **Supply Voltage:** 4.5V to 5.5V
- **Operating Temperature Range:** 0°C to 70°C
- **Clock Frequency:** 32.768 kHz (standard crystal frequency)
- **RAM Capacity:** 64 bytes (50 bytes general-purpose, 14 bytes for clock/control)
- **Timekeeping Functions:** Seconds, minutes, hours, day of week, date, month, year (with leap year correction)
- **Interrupt Output:** Programmable alarm and periodic interrupt
- **Battery Backup Support:** Operates from a backup battery (typically 3V) when main power is off
### **Descriptions:**
- The MC146818AP is a widely used RTC chip in early personal computers (e.g., IBM AT-compatible systems).
- It integrates a real-time clock, calendar, and a small amount of battery-backed RAM for system configuration storage.
- The chip uses an external 32.768 kHz crystal oscillator for accurate timekeeping.
- It includes programmable alarms and periodic interrupts for system wake-up functions.
### **Features:**
- **Battery-Backed Operation:** Maintains time and RAM contents during power loss.
- **Programmable Square-Wave Output:** Can generate clock signals for external use.
- **Binary or BCD Time Representation:** Supports both formats for time/date registers.
- **Three Interrupt Sources:** Time-of-day alarm, periodic rate, and update-ended interrupt.
- **Low Power Consumption:** Optimized for battery-backed applications.
This information is based on the manufacturer's datasheet and historical documentation.
