2-Wire™ RTC
X1202
Real Time Clock/Calendar/Alarms/CPU Supervisor
FEATURES
DESCRIPTION
• Selectable watchdog timer (0.25s, 0.75s, 1.75s, off)
• Power on reset (250ms)
• Programmable low voltage reset
• 2 polled alarms
The X1202 is a Real Time Clock with Clock/Calendar/
CPU Supervisor circuits and two polled alarms. The dual
port clock and alarm registers allow the clock to oper-
ate, without loss of accuracy, even during read and
write operations.
—Settable on the second, minute, hour, day,
month, or day of the week
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 and
automatic adjustment for months with less than 31
days.
• 2-wire interface interoperable with I2C
—400kHz data transfer rate
• Secondary power supply input with internal
switch-over circuitry
• Low power CMOS
—<1µA operating current
—<3mA active current during program
—<400µA active current during data read
• Single byte write capability
• Typical nonvolatile write cycle time: 5ms
• High reliability
The X1202 provides a watchdog timer with 3 selectable
time out periods and off. The watchdog activates a
RESET pin when it expires. The reset also goes active
when V
drops below a fixed trip point. There are two
CC
• Small package options
—8-lead SOIC package, 8-lead TSSOP package
alarms where a match is monitored by polling status bits.
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.
BLOCK DIAGRAM
X1
Timer
Calendar
Logic
Frequency
Divider
1Hz
32.768kHz
Oscillator
Time
X2
Keeping
Registers
(SRAM)
Control
Control
Status
Compare
Registers
Decode
Registers
Alarm
(EEPROM)
Logic
(SRAM)
Serial
Interface
Decoder
SCL
SDA
Alarm Regs
(EEPROM)
8
Interrupt Enable
Alarm
RESET
Characteristics subject to change without notice. 1 of 23
REV 1.1.8 5/17/01
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XICOR [ XICOR INC. ]
