DP8573A Datasheet, PDF (1/16 Pages) National Semiconductor (TI) – Real Time Clock (RTC)

May 1993
DP8573A Real Time Clock (RTC)
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 tech-
nology to provide low standby power in battery back-up en-
vironments 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 integrat-
ed 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 V_BB ^l
V_CC Additionally two supply pins are provided When V_BB
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
Y _{Full function real time clock calendar}
12 24 hour mode timekeeping
Day of week counter
Parallel resonant oscillator
Y _{Power fail features}
Internal power supply switch to external battery
Power Supply Bus glitch protection
Automatic log of time into RAM at power failure
Y _{On-chip interrupt structure}
Periodic alarm and power fail interrupts
Block Diagram
FIGURE 1
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