# DS1287 Real Time Clock

## Features

· Drop-in replacement for IBM AT computer clock/calendar, and MC146818A
· Nonvolatile operation (over 10 years without power)
· Self-contained subsystem including lithium battery, quartz, and support circuitry
· Time and calendar functions: seconds, minutes, hours, day of the week, date, month, year (with leap year compensation)
· Binary or BCD representation of time, calendar, and alarm
· 12/24 hour clock format
· Daylight Savings Time option
· Selectable Motorola/Intel bus timing
· Multiplexed bus
· 64 RAM locations for software interface (14 clock/control registers, 50 general-purpose RAM)
· Programmable square wave output
· Bus-compatible interrupt signals (IRQ)
· Three software-maskable and testable interrupts:
- Time-of-day alarm (once/second to once/day)
- Periodic rates (122 µs to 500 ms)
- End of clock update cycle

## Pin Description

· AD0-AD7: Multiplexed address/data bus
· MOT: Bus type selection
· CS: Chip Select
· AS: Address Strobe
· R/W: Read/Write Input
· DS: Data Strobe
· RESET: Reset Input
· IRQ: Interrupt Request Output
· SQW: Square Wave Output
· VCC: +5 volt supply
· GND: Ground

## Description

· Designed as a direct replacement for the MC146818A.