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X1240S8 Scheda tecnica(PDF) 2 Page - Xicor Inc. |
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X1240S8 Scheda tecnica(HTML) 2 Page - Xicor Inc. |
2 / 19 page X1240 2 PIN CONFIGURATION 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 col- lector 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, respec- tively, 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. Figure 1. Recommended Crystal connection 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 REAL TIME CLOCK OPERATION The Real Time Clock (RTC) uses an external, 32.768KHz quartz crystal to maintain an accurate internal repre- sentation 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 hav- ing 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 dur- ing the course of a read operation. In this device, the time is latched by the read command (falling edge of X1240 X1 X2 VBack VCC NC SCL SDA VSS 1 2 3 4 7 8 6 5 8 pin TSSOP X1240 X1 X2 VBack VCC NC SCL SDA VSS 1 2 3 4 7 8 6 5 8 pin SOIC X1 X2 43pF 18pF 220K 10M VBACK VCC = VBACK -0.2V Internal Voltage VCC |
Codice articolo simile - X1240S8 |
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Descrizione simile - X1240S8 |
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