DS12887A ,Real time clockFEATURES PIN ASSIGNMENT (Top View) Drop-in replacement for IBM AT computerclock/calendarMOT1 24 VC ..
DS12887A ,Real time clockDS12887AReal-Time Clock
DS12887A ,Real time clockDS12887AReal-Time Clock
DS12887A ,Real time clockPIN DESCRIPTION Multiplex bus for pin efficiency AD0–AD7 - Multiplexed Address/Data Bus Interface ..
DS12887A ,Real time clockPIN DESCRIPTION Multiplex bus for pin efficiency AD0–AD7 - Multiplexed Address/Data Bus Interface ..
DS12887A ,Real time clockFEATURES PIN ASSIGNMENT (Top View) Drop-in replacement for IBM AT computerclock/calendarMOT1 24 VC ..
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DS12887A
Real time clock
FEATURESDrop-in replacement for IBM AT computer
clock/calendarPin compatible with the MC146818B and
DS1287ATotally nonvolatile with over 10 years ofoperation in the absence of powerSelf-contained subsystem includes lithium,
quartz, and support circuitryCounts seconds, minutes, hours, days, day of
the week, date, month, and year with leap-year compensation valid up to 2100Binary or BCD representation of time,
calendar, and alarm12-hour or 24-hour clock with AM and PM
in 12-hour modeDaylight Savings Time optionSelectable between Motorola and Intel bus
timingMultiplex bus for pin efficiencyInterfaced with software as 128 RAMlocations
– 14 bytes of clock and control registers
– 114 bytes of general-purpose RAMProgrammable square-wave output signalBus-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�s to 500ms
– End-of-clock update cycleUnderwriters Laboratory (UL) recognized
PIN ASSIGNMENT (Top View)
Package Dimension Informationhttp:///TechSupport/DallasPackInfo.htm
PIN DESCRIPTIONAD0–AD7-Multiplexed Address/Data Bus
N.C.-No ConnectMOT-Bus Type Selection-RTC Chip-Select Input-Address StrobeW-Read/Write Input-Data Strobe
RESET-Reset Input
IRQ-Interrupt Request Output
SQW-Square-Wave Output
VCC-+5V Main Supply
RCLR-RAM ClearGND-Ground
ORDERING INFORMATIONMOT
DS12887A24 PDIP Module (700mil)
N.C.
AD1
AD3
AD4
AD5
AD6
AD7
GND
VCC
SQW
N.C.
IRQ
RESET
N.C.
R/W
N.C.
AD0
AD2
RCLR
DS12887A
Real-Time Clock
DS12887A
DESCRIPTIONThe DS12887A real-time clock plus RAM is designed to be a direct replacement for the DS1287A. The
DS12887A is identical in form, fit, and function to the DS1287A, and includes additional 64 bytes of
general-purpose RAM. Access to this additional RAM space is determined by the logic level presented on
AD6 during the address portion of an access cycle. The RCLRpin is used to clear (set to logic 1) all 114
bytes of general-purpose RAM but does not affect the RAM associated with the real-time clock. In order
to clear the RAM, RCLRmust be forced to an input logic 0 (-0.3V to +0.8V) during battery-backup mode
when VCC is not applied. The RCLRfunction is designed to be used by human interface (shorting to
ground manually or by switch) and not to be driven with external buffers.
For a complete description of operating conditions, electrical characteristics, bus timing and pin
descriptions other than RCLR, refer to the DS12887 data sheet.
Note: Pins 2, 3, 16, 20, and 22 are missing by design. This device cannot be stored or shipped in conductive material that will give a continuitypath between the RAM clear pin and ground.
TYPICAL OPERATING CIRCUIT
:
www.ic-phoenix.com
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