DS12C887

DS12C887 is a Real-Time Clock/Calendar (RTC) with battery-backed nonvolatile RAM from Dallas Semiconductor (now Maxim). It provides timekeeping registers for seconds, minutes, hours, day of week, date, month, and year, plus alarm and periodic interrupt features. It includes nonvolatile RAM to store user data/settings that persists when power is removed. The device is designed as a drop-in RTC replacement for older DS1287 designs and is used to drive system clocks in PCs and embedded systems, as well as for time-stamping and scheduling. It operates from a single supply (typical 5V) with a battery-backup input to preserve time during power loss. It offers a programmable square-wave output and interrupt signaling, and is accessed via a simple register interface (address/data bus). Typical applications include BIOS/RTC timekeeping, embedded timekeeping with nonvolatile storage, and event logging where accurate time reference is needed.

Equivalent products (Dallas/Maxim PC RTCs) include:
- DS1287
- DS1287A
- DS1387
These RTCs with NVRAM are functionally compatible and often drop-in replacements for the DS12C887 in PC/AT-compatible designs.

Key features of the DS12C887 Real-Time Clock/Calendar:
- Real-time clock/calendar with seconds, minutes, hours, day of week, date, month, year (leap-year aware; supports century bit).
- 32.768 kHz crystal input for timekeeping accuracy.
- I2C-like two-wire serial interface with address pins (A0–A2) for multiple devices on the bus.
- Two independent alarms (Alarm 1 and Alarm 2) with flexible masking options.
- Programmable square-wave (SQW/OUT) output with selectable frequencies.
- Battery-backed operation with automatic power-fail switching to preserve time and, typically, RAM.
- Trickle-charge capability to maintain the backup source (external resistor/diode network).
- On-chip RAM/NVRAM for user data (backup memory accessible on the serial bus).
- Interrupt outputs to CPU (IRQ) triggered by alarms or periodic events.
- Low-power operation suitable for battery backup applications.
- Available in small packages (e.g., DIP8/SOIC) for embedded use.
Note: exact RAM size and register formats are vendor-documented; consult the datasheet for precise register map and programming details.

- Pin count: 28-pin DIP (DIP-28).
- Function: CMOS Real-Time Clock/Calendar with nonvolatile RAM (CMOS RAM) for BIOS settings. Provides timekeeping (seconds/minutes/hours/date/day/month/year) and a bank of NVRAM accessible via CMOS/RTC interface (PC CMOS 0x70/0x71 style).

- Manufacturer: Dallas Semiconductor (Dallas Semiconductor Corp.).
- What kind of company: A semiconductor company that designs and manufactures integrated circuits (memory, timing/RTC ICs, analog ICs). Dallas Semiconductor is now part of Maxim Integrated, which is part of Analog Devices.

DS12C887 is a real-time clock/calendar with battery-backed nonvolatile RAM. Typical applications:
- Personal computers and PC-compatible systems (system clock, BIOS time)
- Embedded microcontroller-based designs needing calendar/timebase
- Data loggers and measurement instrumentation for timestamping
- Industrial automation and process control
- Telecommunications, networking equipment, and POS terminals
- Automotive/avionics timekeeping and event stamping
It’s used wherever accurate timekeeping, calendars, and optional alarms with nonvolatile storage are required during power loss.

DS12C887 is an 8-pin RTC. It comes in standard 8-pin packages: PDIP-8 and SO-8 (and other 8-pin SMT variants).