General Description

The DP8573A is intended for use in microprocessor based

systems where information is required for multi-tasking, data

logging or general time of day/date information. This device

is implemented in low voltage silicon gate microCMOS technology

to provide low standby power in battery back-up environments.

The circuit's architecture is such that it looks

like a contiguous block of memory or I/O ports organized as

one block of 32 bytes. This includes the Control Registers,

the Clock Counters, the Alarm Compare RAM, and the Time

Save RAM.

Time and date are maintained from 1/100 of a second to

year and leap year in a BCD format, 12 or 24 hour modes.

Day of week and day of month counters are provided. Time

is controlled by an on-chip crystal oscillator requiring only

the addition of the 32.768 kHz crystal and two capacitors.

Power failure logic and control functions have been integrated

on chip. This logic is used by the RTC to issue a power

fail interrupt, and lock out the mP interface. The time power

fails may be logged into RAM automatically when VBB l

VCC. Additionally, two supply pins are provided. When VBB

l VCC, internal circuitry will automatically switch from the

main supply to the battery supply.

The DP8573A's interrupt structure provides three basic

types of interrupts: Periodic, Alarm/Compare, and Power

Fail. Interrupt mask and status registers enable the masking

and easy determination of each interrupt.

Features

Full function real time clock/calendar

12/24 hour mode timekeeping

Day of week counter

Parallel resonant oscillator

Power fail features

Internal power supply switch to external battery

Power Supply Bus glitch protection

Automatic log of time into RAM at power failure

On-chip interrupt structure

Periodic, alarm, and power fail interrupts