DESCRIPTION

The DS1285 Real Time Chip is a direct replacement for the MC146818A in IBM AT computer clock/calendar and other applications. For a complete description of operating conditions, electrical and mechanical charac

teristics, bus timing, and pin descriptions see the DS12885 data sheet.

FEATURES

• Drop-in replacement for IBM AT computer clock/calendar

• Pin configuration closely matches MC146818A

• Counts seconds, minutes, hours, day of the week,date, month, and year with leap year compensation

• Binary or BCD representation of time, calendar, and alarm

• 12- or 24-hour clock with AM and PM in 12-hour mode

• Daylight Savings Time option

• Selectable between Motorola and Intel bus timing

• Multiplex bus for pin efficiency

• Interfaced with software as 64 RAM locations

– 14 bytes of clock and control registers

– 50 bytes of general purpose RAM

• Programmable square wave output signal

• Bus compatible interrupt signals (IRQ)

• Three interrupts are separately software-maskable and testable

– Time-of-day alarm once/second to once/day

– Periodic rates from 122 µs to 500 ms

– End of clock update cycle

• Optional 28-pin PLCC surface mount package