DS12C887

DS12C887 is Dallas/Maxim’s Real-Time Clock/Calendar with nonvolatile RAM (RTC/NVRAM). It provides a PC-compatible timekeeper with battery-backed memory for system data, suitable for embedded controllers and motherboard use.
Key features:
- Timekeeping: tracks seconds, minutes, hours, day of week, date, month, year; uses a 32.768 kHz crystal.
- Battery-backed RAM: nonvolatile memory to store config/data that is retained when main power is off.
- Alarms and interrupts: programmable alarm(s), periodic interrupt, and a square-wave output.
- PC-compatible interface: register-based I/O interface with an address/data bus, typically decoded in I/O space for compatibility with CMOS/RTC routines.
- Powering: main supply (roughly 4.5–5.5 V) with a separate backup supply (3 V) to keep RTC running during power-down.
- Package options: common in DIP-28 or surface-mount packages.
Typical use: replace or supplement DS1287-era RTCs in PCs and embedded systems to provide reliable timekeeping and persistent configuration data across power cycles.

DS12C887 is a Dallas/Maxim 8042‑compatible keyboard controller (KBC) for IBM PC/AT PS/2 keyboards. Direct equivalents are scarce; closest cross‑refs are other 8042‑compatible KBCs such as Intel 8042 and NEC μPD8042 (and clones). Modern designs often replace the KBC with a microcontroller with PS/2 support or a Super I/O that includes a PS/2 interface. For cross‑reference, compare 8042 compatibility and timing specs in the datasheets.

Here are the common features of the DS12C887 Real-Time Clock/Calendar (Dallas/Maxim):
- Real-time clock and calendar: tracks seconds, minutes, hours, day of week, date, month, year; supports 12/24-hour mode and leap-year handling.
- Time source: uses a 32.768 kHz crystal oscillator for accurate timekeeping.
- Battery-backed operation: maintains time (and often RAM) during power loss via VBAT.
- Battery-backed RAM: non-volatile/user RAM (typical tens of bytes, used for data storage).
- Serial interface: accessible via a simple serial interface for register read/write (addressable time, date, RAM, and control registers).
- Alarm and interrupt: configurable alarm functions with interrupt outputs for timing events.
- Programmable square-wave output: selectable frequencies for clock-output signaling.
- Power-fail detect and safe switching between power rails.
- Operating conditions: designed for low power with a broad supply range and typical industrial temperature range.
Note: exact RAM size, voltage range, and available features can vary by revision; consult the datasheet for precise specifications.

- Pin count: 28-pin package (DIP; also available in other packages).
- Function: Real-Time Clock/Calendar with battery-backed non-volatile RAM (NVRAM); provides time/date registers (seconds, minutes, hours, day, date, month, year), optional alarm/interrupts, and a small NVRAM for BIOS data—PC RTC application.

- Manufacturer: Dallas Semiconductor (DS12C887).
- What kind of company: A semiconductor company that designs and manufactures integrated circuits and microelectronics (RTCs, memory, etc.). Dallas Semiconductor is now part of Maxim Integrated (acquired in 2001).

DS12C887 is a real-time clock/calendar with battery backup used to provide accurate timekeeping when power is removed. Common applications include:
- Embedded controllers/microprocessors in consumer electronics, automotive, and industrial automation
- Computer/firmware RTC for BIOS time, event logging, and time-stamping
- Data loggers, metering, and utility equipment
- Telecommunications and networking hardware for scheduling and time-stamping
- Any portable or low-power device needing a robust, persistent clock/calendar

DS12C887 comes in a 28-pin package (DIP-28). It is also available in surface-mount variants such as PLCC-28 and SOIC-28.