DatasheetsPDF.com

X1240 Dataheets PDF



Part Number X1240
Manufacturers Xicor
Logo Xicor
Description Real Time Clock/Calendar with EEPROM
Datasheet X1240 DatasheetX1240 Datasheet (PDF)

Preliminary Information 16K X1240 Real Time Clock/Calendar with EEPROM DESCRIPTION 2-Wire RTC FEATURES • 2-Wire Interface interoperable with I2C. —400kHz data transfer rate • Secondary Power Supply Input with internal switch-over circuitry. • Year 2000 Compliant • 2K bytes of EEPROM —64 Byte Page Write Mode —3 bit Block Lock • Low Power CMOS —<1µA Operating Current —<3mA Active Current during Program —<400µA Active Current during Data Read • Single Byte Write Capability • Typical Nonvolatile .

  X1240   X1240


Document
Preliminary Information 16K X1240 Real Time Clock/Calendar with EEPROM DESCRIPTION 2-Wire RTC FEATURES • 2-Wire Interface interoperable with I2C. —400kHz data transfer rate • Secondary Power Supply Input with internal switch-over circuitry. • Year 2000 Compliant • 2K bytes of EEPROM —64 Byte Page Write Mode —3 bit Block Lock • 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 —1,000,000 Endurance Cycles —Guaranteed Data Retention: 100 Years • Small Package Options —8-Lead SOIC Package, 8L TSSOP Package The X1240 is a Real Time Clock with clock/calendar circuits. The dual port clock register allows the clock to operate, without loss of accuracy, even during read and write operations. The clock/calendar provides functionality that is controllable and readable through a set of registers. The clock, using a low cost 32.768kHz crystal input, accurately tracks the time in seconds, minutes, hours, date, day, month and years. It has leap year correction, automatic adjustment for the year 2000 and months with less than 31 days. The device offers a backup power input pin. This Vback pin allows the device to be backed up by a nonrechargeable battery. The RTC is fully operational from 1.8 to 5.5 volts. The X1240 provides a 2K byte EEPROM array, giving a safe, secure memory for critical user and configuration data. This memory is unaffected by complete failure of the main and backup supplies. BLOCK DIAGRAM 32.768kHz X1 Oscillator X2 Frequency Divider 1Hz Timer Calendar Logic Time Keeping Registers (SRAM) SCL SDA Serial Interface Decoder Control Decode Logic Control Registers (EEPROM) Status Register (SRAM) 16K EEPROM Array 8 ©Xicor, Inc. 1994, 1995, 1996, 1997, 1998, 1999 Patents Pending 9900-3003.5 12/6/99 CM 1 Characteristics subject to change without notice X1240 PIN CONFIGURATION X1240 8 pin SOIC X1 X2 NC VSS 1 2 3 4 8 7 6 5 VCC VBack SCL SDA 10M 220K X1 X2 Figure 1. Recommended Crystal connection 18pF 43pF VBack VCC X1 X2 X1240 8 pin TSSOP 1 8 2 7 3 6 4 5 SCL SDA VSS NC POWER CONTROL OPERATION The Power control circuit accepts a VCC and a VBACK input. The power control circuit will switch to VBACK when VCC < VBACK - 0.2V. It will switch back to VCC when VCC exceeds VBACK. Figure 2. Power Control VCC VBACK VCC = VBACK -0.2V 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. VBACK This input provides a backup supply voltage to the device. VBACK supplies power to the device in the event the VCC supply fails. X1, X2 The X1 and X2 pins are the input and output, respectively, of an inverting amplifier that can be configured for use as an on-chip oscillator. A 32.768kHz quartz crystal is used. Recommeded crystals are Sieko VT-200 or Epson C-002RX. The crystal supplies a timebase for a clock/oscillator. The internal clock can be driven by an external signal on X1, with X2 left unconnected. Internal Voltage REAL TIME CLOCK OPERATION The Real Time Clock (RTC) uses an external, 32.768KHz quartz crystal to maintain an accurate internal representation of the year, month, day, date, hour, minute, and seconds. The RTC has leap-year correction and a century byte. The clock will also correct for months having fewer than 31 days and will have a bit that controls 24 hour or AM/PM format. When the X1240 powers up after the loss of both VCC and VBACK, the clock will not increment 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 2 X1240 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. 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 seperate buffer at the falling edge of the .


X1228 X1240 X1243


@ 2014 :: Datasheetspdf.com :: Semiconductors datasheet search & download site.
(Privacy Policy & Contact)