12C887 Datasheet: DS12C887





12C887 DS12C887 Datasheet

Part Number 12C887
Description DS12C887
Manufacture Dallas Semiconductor
Total Page 19 Pages
PDF Download Download 12C887 Datasheet PDF

Features: DS12C887 Real Time Clock www.dalsemi.com FEATURES Drop-in replacement for IBM AT computer clock/calendar Pin compatib le with the MC146818B and DS1287 www.Da taSheet4U.com Totally nonvolatile with over 10 years of operation in the absen ce of power Self-contained subsystem in cludes lithium, quartz, and support cir cuitry. Counts seconds, minutes, hours, days, day of the week, date, month, an d year with leap year compensation vali d up to 2100 Binary or BCD representati on of time, calendar, and alarm 12– o r 24–hour clock with AM and PM in 12 hour mode Daylight Savings Time optio n Selectable between Motorola and Intel bus timing Multiplex bus for pin effic iency Interfaced with software as 128 R AM locations – 15 bytes of clock and control registers – 113 bytes of gene ral purpose RAM Programmable square wav e output signal Bus–compatible interr upt signals (IRQ) Three interrupts are separately software maskable and testab le – Time–of–day alarm once/second to once/day – Periodic rates from 122 ms.

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DS12C887
Real Time Clock
www.dalsemi.com
FEATURES
Drop-in replacement for IBM AT computer
clock/calendar
Pin compatible with the MC146818B and
DS1287
www.DataSheet4TUo.ctoamlly nonvolatile with over 10 years of
operation in the absence of power
Self-contained subsystem includes lithium,
quartz, and support circuitry.
Counts seconds, minutes, hours, days, day of
the week, date, month, and year with leap
year compensation valid up to 2100
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 128 RAM
locations
– 15 bytes of clock and control registers
– 113 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 ms to 500 ms
– End of clock update cycle
Century register
PIN ASSIGNMENT
MOT
NC
NC
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
GND
1
2
3
4
5
6
7
8
9
10
11
12
24 VCC
23 SQW
22 NC
21 NC
20 NC
19 IRQ
18 RESET
17 DS
16 NC
15 R/W
14 AS
13 CS
DS12C887 24-Pin
ENCAPSULATED PACKAGE
PIN DESCRIPTION
AD0-AD7 - Multiplexed Address/Data Bus
NC - No Connect
MOT
- Bus Type Selection
CS - RTC Chip Select Input
AS - Address Strobe
R/W - Read/Write Input
DS - Data Strobe
RESET - Reset Input
IRQ
SQW
VCC
GND
- Interrupt Request Output
- Square Wave Output
- +5 Volt Main Supply
- Ground
DESCRIPTION
The DS12C887 Real Time Clock plus RAM is designed as a direct upgrade replacement for the DS12887
in existing IBM compatible personal computers to add hardware year 2000 compliance. A century byte
was added to memory location 50, 32h, as called out by the PC AT specification. A lithium energy
source, quartz crystal, and write-protection circuitry are contained within a 24–pin dual in-line package.
As such, the DS12C887 is a complete subsystem replacing 16 components in a typical application. The
functions include a nonvolatile time-of-day clock, an alarm, a one-hundred-year calendar, programmable
interrupt, square wave generator, and 113 bytes of nonvolatile static RAM. The real time clock is
distinctive in that time-of-day and memory are maintained even in the absence of power.
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