Description
The CDP1879 real-time clock supplies time and calendar information from seconds to months in BCD format. It consists of 5 separately addressable and programmable counters that divide down an oscillator input. The clock input can have any one of 4 possible frequencies, allowing flexibility in the choice of crystal or external clock sources. Using an external 32kHz clock source, timekeeping can be performed down to 2.5V (see Standby (Timekeeping) Voltage Operation).

FEATUREs
• CPU Interface for Use with General-Purpose Microprocessors
• Time Of Day/Calendar
• Reads Seconds, Minutes, Hours
• Reads Day of Month and Month
• Alarm Circuit With Seconds, Minutes or Hours Operation
• Power Down Mode
• Separate Clock Output Selects 1 of 15 Square Wave Signals
• Interrupt Output Activated By Clock Output and/or Alarm Circuit
• Date Integrity Sampling for Clock Rollover Eliminated
• On-Board Oscillator:
    - Crystal Operation CDP1879 at 10V. . . . . . . 4.19MHz, 2.09MHz or 1.048MHz
    - Crystal Operation CDP1879C-1 at 5V . . . . . 4.19MHz, 2.09MHz or 1.048MHz or 32kHz
    - External Clock Operation at 10V or 5V. . . . 4.19MHz, 2.09MHz, 1.048MHz or 32kHz
• Addressable in Memory Space or CDP1800 Series I/O Mode
• Low Standby (Timekeeping) Voltage with External Clock
• Related Literature
    - AN7275, Guide to the Use of CD1879 and CDP1879C1 Real Time Clock