DS12887A (RTC).pdf
(
181 KB
)
Pobierz
DS12887A
Real-Time Clock
www.maxim-ic.com
www.maxim-ic.com
FEATURES
PIN ASSIGNMENT (Top View)
Drop-in replacement for IBM AT computer
clock/calendar
MOT
1
2
3
4
5
6
7
8
9
10
11
12
24
V
CC
SQW
NC
Pin compatible with the MC146818B and
DS1287A
N.C.
23
N.C.
22
21
20
19
18
17
16
15
14
13
AD0
RCLR
Totally nonvolatile with over 10 years of
operation in the absence of power
AD1
N.C.
IRQ
RESET
DS
N.C.
R/W
AS
CS
AD2
Self-contained subsystem includes lithium,
quartz, and support circuitry
AD3
AD4
AD5
AD6
AD7
GND
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
DS12887A
24 PDIP Module (700mil)
12-hour or 24-hour clock with AM and PM
in 12-hour mode
Package Dimension Information
http://www.maxim-ic.com/TechSupport/DallasPackInfo.htm
Daylight Savings Time option
Selectable between Motorola and Intel bus
timing
PIN DESCRIPTION
AD0–AD7 -
Multiplex bus for pin efficiency
Multiplexed Address/Data Bus
Interfaced with software as 128 RAM
locations
– 14 bytes of clock and control registers
– 114 bytes of general-purpose RAM
N.C.
-
No Connect
M
OT
-
Bus Type Selection
-
RTC Chip-Select Input
CS
A
S
-
Address Strobe
Programmable square-wave output signal
R/ W
-
Read/Write Input
Bus-compatible interrupt signals (IRQ)
DS
-
Data Strobe
Three interrupts are separately software-
maskable and testable
– Time-of-day alarm once/second to
once/day
– Periodic rates from 122
-
Reset Input
RES
ET
-
Interrupt Request Output
IRQ
SQW
-
Square-Wave Output
V
CC
-
+5V Main Supply
s to 500ms
– End-of-clock update cycle
-
RAM Clear
RCLR
Underwriters Laboratory (UL) recognized
GND
-
Ground
ORDERING INFORMATION
PART
PIN-PACKAGE
TOP MARK
TEMP RANGE
DS12887A
24 PDIP Module
DS12887A
0°C to +70°C
Note:
Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device
may be simultaneously available through various sales channels. For information about device errata, click here:
http://www.maxim-ic.com/errata
.
1 of 2
073102
DS12887A
DESCRIPTION
The 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 sp
ace is
determined by the logic level presented on
AD6 during the address portion of an access cycle. The
RCLR
pin is used to clear (set to logic 1) all 114
bytes of general-pu
rpose
RAM but does not affect the RAM associated with the real-time clock. In order
to clear the RAM,
RCLR
must be
force
d to an input logic 0 (-0.3V to +0.8V) during battery-backup mode
when V
CC
is not applied. The
RCLR
function 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 descr
iption
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 continuity
path between the RAM clear pin and ground.
TYPICAL OPERATING CIRCUIT
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This datasheet has been download from:
www.datasheetcatalog.com
Datasheets for electronics components.
Plik z chomika:
AndyMaster
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