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PDF ( 数据手册 , 数据表 ) X1205

零件编号 X1205
描述 Real Time Clock/Calendar
制造商 Xicor
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X1205 数据手册, 描述, 功能
Preliminary Information
New Features
Repetitive Alarms &
Temperature Compensation
X1205
Real Time Clock/Calendar
2-WireRTC
FEATURES
• Real Time Clock/Calendar
—Tracks time in Hours, Minutes, and Seconds
—Day of the Week, Day, Month, and Year
• 2 Polled Alarms (Non-volatile)
—Settable on the Second, Minute, Hour, Day of
the Week, Day, or Month
—Repeat Mode (periodic interrupts)
• Oscillator Compensation on chip
—Internal feedback resistor and compensation
capacitors
—64 position Digitally Controlled Trim Capacitor
—6 digital frequency adjustment settings to
±30ppm
• Battery Switch or Super Cap Input
• 2-Wire™ Interface interoperable with I2C*
—400kHz data transfer rate
• Low Power CMOS
—1.25µA Operating Current (Typical)
• Small Package Options
—8-Lead SOIC and 8-Lead TSSOP
APPLICATIONS
• Utility Meters
• HVAC Equipment
• Audio / Video Components
• Set Top Box / Television
• Modems
• Network Routers, Hubs, Switches, Bridges
• Cellular Infrastructure Equipment
• Fixed Broadband Wireless Equipment
• Pagers / PDA
• POS Equipment
• Test Meters / Fixtures
• Office Automation (Copiers, Fax)
• Home Appliances
• Computer Products
• Other Industrial / Medical / Automotive
DESCRIPTION
The X1205 device is a Real Time Clock with clock/
calendar, two polled alarms, oscillator compensation,
and battery backup switch.
The oscillator uses an external, low-cost 32.768kHz
crystal. All compensation and trim components are
integrated on the chip. This eliminates several external
discrete components and a trim capacitor, saving
board area and component cost.
The Real-Time Clock keeps track of time with separate
registers for Hours, Minutes, and Seconds. The
Calendar has separate registers for Date, Month, Year
and Day-of-week. The calendar is correct through
2099, with automatic leap year correction.
BLOCK DIAGRAM
OSC
Compensation
32.768kHz
X1
X2
Oscillator
Frequency 1Hz
Divider
Timer
Calendar
Logic
Time
Keeping
Registers
(SRAM)
SCL
SDA
Serial
Interface
Decoder
IRQ
Control
Decode
Logic
8
*I2C is a Trademark of Philips.
REV 1.0.9 8/29/02
Control
Registers
(EEPROM)
Status
Registers
(SRAM)
Interrupt Enable
Alarm
www.xicor.com
Alarm
Compare
Alarm Regs
(EEPROM)
Characteristics subject to change without notice. 1 of 22







X1205 pdf, 数据表
X1205 – Preliminary Information
Figure 3. Valid Data Changes on the SDA Bus
SCL
SDA
Data Stable
Data Change
Data Stable
Figure 4. Valid Start and Stop Conditions
SCL
SDA
Start
Figure 5. Acknowledge Response From Receiver
SCL from
Master
Data Output
from Transmitter
1
Data Output
from Receiver
Start
Stop
89
Acknowledge
In the read mode, the device will transmit eight bits of
data, release the SDA line, then monitor the line for an
acknowledge. If an acknowledge is detected and no
stop condition is generated by the master, the device
will continue to transmit data. The device will terminate
further data transmissions if an acknowledge is not
detected. The master must then issue a stop condition
to return the device to Standby mode and place the
device into a known state.
DEVICE ADDRESSING
Following a start condition, the master must output a
Slave Address Byte. Slave bits ‘1101’ access the CCR.
Bit 3 through Bit 1 of the slave byte specify the device
select bits. These are set to ‘111’.
The last bit of the Slave Address Byte defines the oper-
ation to be performed. When this R/W bit is a one, then
a read operation is selected. A zero selects a write
operation. Refer to Figure 6.
After loading the entire Slave Address Byte from the
SDA bus, the X1205 compares the device identifier
and device select bits with ‘1101111’. Upon a correct
compare, the device outputs an acknowledge on the
SDA line.
REV 1.0.9 8/29/02
www.xicor.com
Characteristics subject to change without notice. 8 of 22







X1205 equivalent, schematic
X1205 – Preliminary Information
APPLICATION SECTION
CRYSTAL OSCILLATOR AND TEMPERATURE
COMPENSATION
Xicor has now integrated the oscillator compensation
circuity on-chip, to eliminate the need for external com-
ponents and adjust for crystal drift over temperature
and enable very high accuracy timekeeping (<5ppm
drift).
The Xicor RTC family uses an oscillator circuit with on-
chip crystal compensation network, including adjust-
able load-capacitance. The only external component
required is the crystal. The compensation network is
optimized for operation with certain crystal parameters
which are common in many of the surface mount or
tuning-fork crystals available today. Table 6 summa-
rizes these parameters.
Table 7 contains some crystal manufacturers and part
numbers that meet the requirements for the Xicor RTC
products.
The turnover temperature in Table 6 describes the
temperature where the apex of the of the drift vs. tem-
perature curve occurs. This curve is parabolic with the
drift increasing as (T-T0)2. For an Epson MC-405
device, for example, the turnover temperature is typi-
cally 25 deg C, and a peak drift of >110ppm occurs at
the temperature extremes of –40 and +85 deg C. It is
possible to address this variable drift by adjusting the
load capacitance of the crystal, which will result in pre-
dictable change to the crystal frequency. The Xicor
RTC family allows this adjustment over temperature
since the devices include on-chip load capacitor trim-
ming. This control is handled by the Analog Trimming
Register, or ATR, which has 6 bits of control . The load
capacitance range covered by the ATR circuit is
approximately 3.25pF to 18.75pF, in 0.25pf incre-
ments. Note that actual capacitance would also
include about 2pF of package related capacitance. In-
circuit tests with commercially available crystals dem-
onstrate that this range of capacitance allows fre-
quency control from +116ppm to –37ppm, using a
12.5pF load crystal.
In addition to the analog compensation afforded by the
adjustable load capacitance, a digital compensation
feature is available for the Xicor RTC family. There are
three bits known as the Digital Trimming Register or
DTR, and they operate by adding or skipping pulses in
the clock signal. The range provided is ±30ppm in
increments of 10ppm. The default setting is 0ppm. The
DTR control can be used for coarse adjustments of
frequency drift over temperature or for crystal initial
accuracy correction.
Table 6. Crystal Parameters Required for Xicor RTC’s
Parameter
Min Typ Max
Frequency
32.768
Freq. Tolerance
±100
Turnover Temperature
20 25 30
Operating Temperature Range
Parallel Load Capacitance
Equivalent Series Resistance
-40
12.5
85
50
Units
kHz
ppm
°C
°C
pF
k
Notes
Down to 20ppm if desired
Typically the value used for most
crystals
For best oscillator performance
Table 7. Crystal Manufacturers
Manufacturer
Part Number
Citizen
Epson
CM201, CM202, CM200S
MC-405, MC-406
Raltron
RSM-200S-A or B
SaRonix
Ecliptek
32S12A or B
ECPSM29T-32.768K
ECS
ECX-306/ECX-306I
Fox FSM-327
Temp Range
-40 to +85°C
-40 to +85°C
-40 to +85°C
-40 to +85°C
-10 to +60°C
-10 to +60°C
-40 to +85°C
+25°C Freq Toler.
±20ppm
±20ppm
±20ppm
±20ppm
±20ppm
±20ppm
±20ppm
REV 1.0.9 8/29/02
www.xicor.com
Characteristics subject to change without notice. 16 of 22










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