x1205s8izt1 Intersil Corporation, x1205s8izt1 Datasheet - Page 7

• Manufacturer Part Number: x1205s8izt1
• Description: 2-wire? Rtc Real Time Clock/calendar
• Manufacturer: Intersil Corporation

DESCRIPTION (continued)
The powerful Dual Alarms can be set to any
Clock/Calendar value for a match. For instance, every
minute, every Tuesday, or 5:23 AM on March 21. The
alarms can be polled in the Status Register or provide
a hardware interrupt (IRQ Pin).
mode for the alarms allowing a periodic interrupt.
The device offers a backup power input pin. This
V
battery or SuperCap. The entire X1205 device is fully
operational
clock/calendar portion of the X1205 device remains
fully operational down to 1.8 volts (Standby Mode).
PIN DESCRIPTIONS
Serial Clock (SCL)
The SCL input is used to clock all data into and out of
the device. The input buffer on this pin is always active
(not gated).
Serial Data (SDA)
SDA is a bidirectional pin used to transfer data into and
out of the device. It has an open drain output and may
be wire ORed with other open drain or open collector
outputs. The input buffer is always active (not gated).
An open drain output requires the use of a pull-up
resistor. The output circuitry controls the fall time of
the output signal with the use of a slope controlled
pull-down. The circuit is designed for 400kHz 2-wire
interface speeds.
V
This input provides a backup supply voltage to the
device. V
event the V
to a battery, a Supercap or tied to ground if not used.
Interrupt Output – IRQ
This is an interrupt signal output. This signal notifies a
host processor that an alarm has occurred and
requests action. It is an open drain active low output.
NC = No internal connection
BACK
BACK
IRQ
V
X1
X2
SS
pin allows the device to be backed up by
BACK
8-Pin SOIC
1
2
3
4
CC
from
supply fails. This pin can be connected
supplies power to the device in the
8
7
6
5
2.7
V
V
SCL
SDA
CC
BACK
X1205
to
7
V
BACK
V
5.5
CC
X1
X2
There is a repeat
8-Pin TSSOP
volts
1
2
3
4
8
7
6
5
and
SCL
SDA
V
IRQ
SS
the
X1205
X1, X2
The X1 and X2 pins are the input and output,
respectively, of an inverting amplifier. An external
32.768kHz quartz crystal is used with the X1205 to
supply a timebase for the real time clock. The
recommended crystal is a Citizen CFS206-32.768KDZF.
Internal compensation circuitry is included to form a
complete oscillator circuit. Care should be taken in the
placement of the crystal and the layout of the circuit.
Plenty of ground plane around the device and short
traces to X1 and X2 are highly recommended. See
Application section for more recommendations.
Figure 2. Recommended Crystal connection
POWER CONTROL OPERATION
The power control circuit accepts a V
input. The power control circuit powers the clock from
V
power the device from V
Figure 3. Power Control
REAL TIME CLOCK OPERATION
The Real Time Clock (RTC) uses an external
32.768kHz quartz crystal to maintain an accurate
internal representation of second, minute, hour, day,
date, month, and year. The RTC has leap-year correc-
tion. The clock also corrects for months having fewer
than 31 days and has a bit that controls 24 hour or
AM/PM format. When the X1205 powers up after the
loss of both V
until at least one byte is written to the clock register.
Reading the Real Time Clock
The RTC is read by initiating a Read command and
specifying the address corresponding to the register of
the Real Time Clock. The RTC Registers can then be
read in a Sequential Read Mode. Since the clock runs
continuously and a read takes a finite amount of time,
there is the possibility that the clock could change during
the course of a read operation. In this device, the time is
latched by the read command (falling edge of the clock
BACK
V
BACK
when V
CC
CC
Off
and V
< V
V
BACK
CC
BACK
CC
- 0.2V. It will switch back to
when V
, the clock will not operate
X1
X2
Voltage
CC
exceeds V
CC
and a V
September 23, 2005
On
FN8097.2
BACK
BACK
In
.