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