National Semiconductor DP8573A Real Time Clock Manual

About this manual

This manual describes the DP8573A real‑time clock (RTC) intended for microprocessor‑based systems. It covers the device architecture, including control registers, clock counters, alarm compare RAM, and time‑save RAM, and explains how the on‑chip crystal oscillator and power‑fail logic operate.

Detailed sections include absolute maximum ratings, electrical characteristics, timing waveforms, pin descriptions, functional operation (reading, writing, and interrupt handling), and power‑failure circuitry. The document also provides connection diagrams and programming guidelines for reliable integration of the RTC into hardware designs.

What's inside

• General Description
• Absolute Maximum Ratings
• Electrical Characteristics
• Timing Waveforms
• Pin Description
• Functional Description
• Reading the Clock
• Initializing and Writing to the Calendar‑Clock
• Interrupt Logic
• Power‑Fail Circuitry

Specifications

Frequently asked questions

What crystal frequency is required for the DP8573A RTC?

The DP8573A uses a 32.768 kHz crystal connected to the OSC IN/OUT pins.

How does the DP8573A handle a power failure?

When VCC falls below VBB, the device switches to the backup battery, logs the time into RAM, and can generate a power‑fail interrupt.

What are the three basic interrupt types provided by the DP8573A?

The device provides Periodic, Alarm/Compare, and Power‑Fail interrupts.

Which pins are used for the crystal oscillator?

OSC IN (input) and OSC OUT (output) connect the external crystal to the internal parallel resonant oscillator.