DataSheet.es X1227 Hoja de datos PDF



PDF X1227 Datasheet ( Hoja de datos )

Número de pieza X1227
Descripción RTC Real TimeClock/Calendar/ CPU Supervisor
Fabricantes Intersil Corporation 
Logotipo Intersil Corporation Logotipo
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X1227 datasheet

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X1227 pdf
X1227
(9) VSDA =VSCL=VBACK, Others = GND or VBACK
(10)VSDA = GND or VCC, VSCL = GND or VCC, VRESET = GND or VCC
(11)IOL = 3.0mA at 5.5V, 1.5mA at 2.7V
(12) IOH = -1.0mA at 5.5V, -0.4mA at 2.7V
(13)Threshold voltages based on the higher of Vcc or Vback.
(14)Using recommended crystal and oscillator network applied to X1 and X2 (25°C).
(15)Typical values are for TA = 25°C
Capacitance TA = 25°C, f = 1.0 MHz, VCC = 5V
Symbol
Parameter
Max.
Units
Test Conditions
COUT(1)
CIN(1)
Output Capacitance (SDA, RESET)
Input Capacitance (SCL)
10 pF
10 pF
VOUT = 0V
VIN = 0V
Notes: (1) This parameter is not 100% tested.
(2) The input capacitance between x1 and x2 pins can be varied between 5pF and 19.75pF by using analog trimming registers
AC CHARACTERISTICS
AC Test Conditions
Input Pulse Levels
Input Rise and Fall Times
Input and Output Timing
Levels
Output Load
VCC x 0.1 to VCC x 0.9
10ns
VCC x 0.5
Standard Output Load
Figure 1. Standard Output Load for testing the device with VCC = 5.0V
Equivalent AC Output Load Circuit for VCC = 5V
5.0V
SDA
1533Ω
For VOL= 0.4V
and IOL = 3 mA
100pF
5 FN8099.2
May 8, 2006

5 Page

X1227 arduino
X1227
POWER CONTROL OPERATION
The power control circuit accepts a VCC and a VBACK
input. The power control circuit powers the device from
VBACK when VCC < VBACK - 0.2V. It will switch back to
power the device from VCC when VCC exceeds VBACK.
Figure 3. Power Control
VBACK
VCC
Off
Voltage
On
In
REAL TIME CLOCK OPERATION
The Real Time Clock (RTC) uses an external
32.768kHz quartz crystal to maintain an accurate inter-
nal representation of the 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 X1227 powers up after the
loss of both VCC and VBACK, the clock will not operate
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
on the ACK bit prior to RTC data output) into a separate
latch to avoid time changes during the read operation.
The clock continues to run. Alarms occurring during a
read are unaffected by the read operation.
Writing to the Real Time Clock
The time and date may be set by writing to the RTC
registers. To avoid changing the current time by an
uncompleted write operation, the current time value is
loaded into a separate buffer at the falling edge of the
clock on the ACK bit before the RTC data input bytes,
the clock continues to run. The new serial input data
replaces the values in the buffer. This new RTC value
is loaded back into the RTC Register by a stop bit at
the end of a valid write sequence. An invalid write
operation aborts the time update procedure and the
contents of the buffer are discarded. After a valid write
operation the RTC will reflect the newly loaded data
beginning with the next “one second” clock cycle after
the stop bit is written. The RTC continues to update
the time while an RTC register write is in progress and
the RTC continues to run during any nonvolatile write
sequences. A single byte may be written to the RTC
without affecting the other bytes.
Accuracy of the Real Time Clock
The accuracy of the Real Time Clock depends on the
frequency of the quartz crystal that is used as the time
base for the RTC. Since the resonant frequency of a
crystal is temperature dependent, the RTC perfor-
mance will also be dependent upon temperature. The
frequency deviation of the crystal is a fuction of the
turnover temperature of the crystal from the crystal’s
nominal frequency. For example, a >20ppm frequency
deviation translates into an accuracy of >1 minute per
month. These parameters are available from the
crystal manufacturer. Intersil’s RTC family provides
on-chip crystal compensation networks to adjust load-
capacitance to tune oscillator frequency from +116
ppm to -37 ppm when using a 12.5 pF load crystal. For
more detail information see the Application section.
CLOCK/CONTROL REGISTERS (CCR)
The Control/Clock Registers are located in an area
separate from the EEPROM array and are only
accessible following a slave byte of “1101111x” and
reads or writes to addresses [0000h:003Fh]. The
clock/control memory map has memory addresses
from 0000h to 003Fh. The defined addresses are
described in the Table 1. Writing to and reading from
the undefined addresses are not recommended.
CCR access
The contents of the CCR can be modified by perform-
ing a byte or a page write operation directly to any
address in the CCR. Prior to writing to the CCR
(except the status register), however, the WEL and
RWEL bits must be set using a two step process (See
section “Writing to the Clock/Control Registers.”)
The CCR is divided into 5 sections. These are:
1. Alarm 0 (8 bytes; non-volatile)
2. Alarm 1 (8 bytes; non-volatile)
3. Control (4 bytes; non-volatile)
4. Real Time Clock (8 bytes; volatile)
5. Status (1 byte; volatile)
Each register is read and written through buffers. The
non-volatile portion (or the counter portion of the RTC)
is updated only if RWEL is set and only after a valid
write operation and stop bit. A sequential read or page
write operation provides access to the contents of only
one section of the CCR per operation. Access to
another section requires a new operation. Continued
10 FN8099.2
May 8, 2006

10 Page





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