DS1678

Real Time Clock Overview

The DS1678 is a real-time clock (RTC) event recorder that logs the time and date of asynchronous events triggered by the INT pin. It records seconds, minutes, hours, date, day of the week, month, year, and century in BCD format with leap-year compensation. The device features a 16-bit elapsed time counter (ETC) and logs up to 1025 consecutive events in read-only battery-backed memory. It includes 32 bytes of general-purpose NV RAM and an I2C serial interface. Operating from VCC or VBAT, it supports power-supply voltages from 4.5V to 5.5V and functions within an industrial temperature range of -40°C to +85°C.

Real Time Clock Feature Summary

• Logs up to 1025 consecutive events in read-only battery-backed memory using a 16-bit elapsed time counter.
• Real-time clock/calendar in BCD format with leap-year compensation and Year 2000 compliance.
• User-programmable event trigger selectable for falling edge, rising edge, or both edges of the INT pin.
• Includes 32-byte battery-backed general-purpose NV RAM and programmable RTC alarm.

Real Time Clock Applications

• Recording timestamps for nonperiodic, asynchronous system events.
• Monitoring equipment uptime and failure intervals via elapsed time logging.
• Industrial data acquisition where event timing accuracy is critical.

Real Time Clock Procurement Notes

Verify the specific package variant required, such as Plastic DIP (DS1678), SO (DS1678S), or Tape and Reel (DS1678S+T&R). Confirm lead-free status if indicated by the '+' suffix. Ensure the design accounts for the 4.5V to 5.5V VCC operating range and the -40°C to +85°C industrial temperature specifications during component sourcing.

Real Time Clock Selection Notes

Select the DS1678 when event logging capacity exceeds standard RTC capabilities. Choose the seconds resolution for high-frequency events (up to 18.2 hours between events) or hours resolution for low-frequency monitoring (up to 7.5 years between events). Ensure the application provides a stable 32.768kHz crystal with a 12.5pF load capacitance for optimal clock accuracy.

Real Time Clock Part Context

The DS1678 belongs to the Maxim Integrated/Analog Devices DS1678 series of real-time clocks. It is distinct from standard RTCs by its dedicated event-logging architecture, which automatically captures elapsed time durations upon INT pin activation. The series includes variants like the DS1678K evaluation board and different packaging options to suit various assembly requirements.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation. Verify compatibility with existing I2C bus protocols and interrupt handling logic if considering alternative RTC event loggers.

Real Time Clock FAQ

How does the DS1678 handle memory rollover?

The device can be configured to enable or disable rollover. If enabled, new data overwrites old data starting from the Start Time Stamp Register after 1025 events. If disabled, recording stops after 1025 events, though the event counter continues to increment.

What triggers an event log entry?

An event is logged when the INT pin is activated. The trigger can be programmed to respond to the falling edge, rising edge, or both rising and falling edges via the TRx bits in the Control Register.

What is the function of the MEM CLR bit?

The MEM CLR bit must be set to one to start an event-log mission. This action clears the Event-Log Memory, Event Count, ETC, Address Pointer, and Start Time Stamp registers to ensure a fresh logging session.