DS1558

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CER

the RTC outputs data on DQ0–DQ7.

OE

– Output-enable input that is used to access the RTC and the external SRAM.

OER

also low, the RTC outputs data on DQ0–DQ7.

WE

– Write-enable input that is used to write data to the RTC registers.

for the 3.3V version) is applied within normal limits, the device is fully accessible and data can be written

N.C. – No internal connection.

X1, X2 – Connections for a standard 32.768kHz quartz crystal. The internal oscillator circuitry is

information about crystal selection and crystal layout considerations, refer to Application Note 58

“Crystal Considerations with Dallas Real-Time Clocks.” The DS1558 can also be driven by an external

32.768kHz oscillator. In this configuration, the X1 pin is connected to the external oscillator signal and

the X2 pin is floated.

must be held between 2.5V and 3.7V for proper operation. UL recognized to ensure against reverse

charging current when used with a lithium battery. If only one battery is used, it should be attached to

See “Conditions of Acceptability” at http://www.maxim-ic.com/TechSupport/QA/ntrl.htm.