Preliminary Information
9900-3003.5 12/6/99 CM
Xicor, Inc. 1994, 1995, 1996, 1997, 1998, 1999 Patents Pending
1
Characteristics subject to change without notice
16K
2-Wire RTC
Real Time Clock/Calendar with EEPROM
FEATURES
2-Wire Interface interoperable with I
—400kHz data transfer rate
Secondary Power Supply Input with internal
switch-over circuitry.
Year 2000 Compliant
2K bytes of EEPROM
—64 Byte Page Write Mode
—3 bit Block Lock
Low Power CMOS
—<1
μ
A Operating Current
—<3mA Active Current during Program
—<400
μ
A Active Current during Data Read
Single Byte Write Capability
Typical Nonvolatile Write Cycle Time: 5ms
High Reliability
—1,000,000 Endurance Cycles
—Guaranteed Data Retention: 100 Years
Small Package Options
—8-Lead SOIC Package, 8L TSSOP Package
2
C.
DESCRIPTION
The X1240 is a Real Time Clock with clock/calendar
circuits. The dual port clock register allows the clock to
operate, without loss of accuracy, even during read and
write operations.
The clock/calendar provides functionality that is con-
trollable and readable through a set of registers. The
clock, using a low cost 32.768kHz crystal input, accu-
rately tracks the time in seconds, minutes, hours, date,
day, month and years. It has leap year correction,
automatic adjustment for the year 2000 and months
with less than 31 days.
The device offers a backup power input pin. This
Vback pin allows the device to be backed up by a non-
rechargeable battery. The RTC is fully operational
from 1.8 to 5.5 volts.
The X1240 provides a 2K byte EEPROM array, giving
a safe, secure memory for critical user and configura-
tion data. This memory is unaffected by complete fail-
ure of the main and backup supplies.
BLOCK DIAGRAM
X1
X2
Oscillator
Frequency
Divider
Timer
Calendar
Logic
8
32.768kHz
Control
Registers
1Hz
Time
Keeping
Registers
(SRAM)
Control
Decode
Logic
(EEPROM)
SCL
SDA
Serial
Interface
Decoder
16K
EEPROM
Array
Register
Status
(SRAM)
X1240