Preliminary Information
16K
X1241
2-Wire
™
RTC
Real Time Clock/Calendar/CPU Supervisor with EEPROM
FEATURES
• Programmable low voltage reset
• Selectable watchdog timer (1.75s, 750ms,
250ms, off)
• 2-wire interface interoperable with I
2
C
—400kHz data transfer rate
• Secondary power supply input with internal
switch-over circuitry
• 2Kbytes 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
• Small package options
—8-lead SOIC package, 8-lead TSSOP package
DESCRIPTION
The X1241 is a Real Time Clock with clock/calendar
circuits and a selectable watchdog timer. 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
V
BACK
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 X1241 provides a 2Kbyte EEPROM array, giving a
safe, secure memory for critical user and configuration
data. This memory is unaffected by complete failure of
the main and backup supplies.
BLOCK DIAGRAM
32.768kHz
X1
Oscillator
X2
Frequency
Divider
1Hz
Timer
Calendar
Logic
Time
Keeping
Registers
(SRAM)
SCL
SDA
Control
Decode
Logic
Serial
Interface
Decoder
8
Control
Registers
(EEPROM)
Status
Register
(SRAM)
16Kbit
EEPROM
Array
Watchdog
Timer
Low Voltage
Reset
RESET
REV 1.1.3 2/13/01
www.xicor.com
Characteristics subject to change without notice.
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XICOR [ XICOR INC. ]
