isl12022m Intersil Corporation, isl12022m Datasheet - Page 10

• Manufacturer Part Number: isl12022m
• Description: Real Time Clock With Embedded Crystal, ??5ppm Accuracy
• Manufacturer: Intersil Corporation

The device Time Stamps the switchover from V
and V
registers respectively. If multiple V
occur before the status is read, the earliest V
power-down time is stored and the most recent V
time is stored.
Temperature conversion and compensation can be enabled
in battery backup mode. Bit BTSE in the BETA register
controls this operation, as described in “BETA Register
(BETA)” on page 17.
Power Failure Detection
The ISL12022M provides a Real Time Clock Failure Bit
(RTCF) to detect total power failure. It allows users to
determine if the device has powered up after having lost all
power to the device (both V
Brownout Detection
The ISL12022M monitors the V
provides warning if the V
levels. There are six (6) levels that can be selected for the
trip level. These values are 85% below popular V
The LVDD bit in the Status Register will be set to “1” when
brownout is detected. Note that the I
active unless the Battery V
Battery Level Monitor
The ISL12022M has a built-in warning feature once the
backup battery level drops first to 85% and then to 75% of
the battery’s nominal V
drops to between 85% and 75%, the LBAT85 bit is set in the
status register. When the level drops below 75%, both
LBAT85 and LBAT75 bits are set in the status register.
There is a Battery Time Stamp Function available. Once the
V
RTC time/date are written into the TSV2B register. This
information can be read from the TSV2B registers to discover
the point in time of the V
power-down cycles before reading these registers, the first
values stored in these registers will be retained. These
registers will hold the original power-down value until they are
cleared by setting CLRTS = 1 to clear the registers.
The normal power switching of the ISL12022M is designed
to switch into battery backup mode only if the V
lost. This will ensure that the device can accept a wide range
of backup voltages from many types of sources while reliably
switching into backup mode.
Note that the ISL12022M is not guaranteed to operate with
V
than this minimum, correct operation of the device, (especially
after a V
DD
BAT
is low enough to enable switchover to the battery, the
BAT
< 1.8V. If the battery voltage is expected to drop lower
DD
to V
power-down cycle) is not guaranteed.
DD
, and the time is stored in t
BAT
DD
DD
TRIP
level. When the battery voltage
power-down. If there are multiple
DD
level drops below prescribed
10
and V
DD
levels are reached.
DD
level continuously and
2
power-down sequences
BAT
C serial bus remains
).
SV2B
DD
DD
DD
to V
BAT
and t
DD
to V
power is
BAT
to V
levels.
SB2V
BAT
DD
ISL12022M
Real Time Clock Operation
The Real Time Clock (RTC) uses an integrated 32.768kHz
quartz crystal to maintain an accurate internal representation
of second, minute, hour, day of week, date, month, and year.
The RTC also has leap-year correction. 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
ISL12022M powers up after the loss of both V
the clock will not begin incrementing until at least one byte is
written to the clock register.
Single Event and Interrupt
The alarm mode is enabled via the MSB bit. Choosing single
event or interrupt alarm mode is selected via the IM bit. Note
that when the frequency output function is enabled, the
alarm function is disabled.
The standard alarm allows for alarms of time, date, day of
the week, month, and year. When a time alarm occurs in
single event mode, the IRQ/F
the alarm status bit (ALM) will be set to “1”.
The pulsed interrupt mode allows for repetitive or recurring
alarm functionality. Hence, once the alarm is set, the device
will continue to alarm for each occurring match of the alarm
and present time. Thus, it will alarm as often as every minute
(if only the nth second is set) or as infrequently as once a
year (if at least the nth month is set). During pulsed interrupt
mode, the IRQ/F
the alarm status bit (ALM) will be set to “1”.
The ALM bit can be reset by the user or cleared automatically
using the auto reset mode (see ARST bit). The alarm function
can be enabled/disabled during battery backup mode using
the FOBATB bit. For more information on the alarm, please
see “ALARM Registers (10h to 15h)” on page 18.
Frequency Output Mode
The ISL12022M has the option to provide a clock output
signal using the IRQ/F
frequency output mode is set by using the FO bits to select
15 possible output frequency values from 1/32Hz to 32kHz.
The frequency output can be enabled/disabled during
Battery Backup mode using the FOBATB bit.
General Purpose User SRAM
The ISL12022M provides 128 bytes of user SRAM. The
SRAM will continue to operate in battery backup mode.
However, it should be noted that the I
battery backup mode.
I
The ISL12022M has an I
access to the control and status registers and the user
SRAM. The I
industry I
signal (SDA) and a clock signal (SCL).
2
C Serial Interface
2
C serial bus protocols using a bi-directional data
2
C serial interface is compatible with other
OUT
pin will be pulled low for 250ms and
OUT
2
C serial bus interface that provides
open drain output pin. The
OUT
pin will be pulled low and
2
C bus is disabled in
DD
December 18, 2008
and V
FN6668.4
BAT
,