AN968

2/4

Doc ID 6255 Rev 2

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General timekeeping (i.e. seconds, hour, date, year,...)

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Time stamping (data collection correlated against time)

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Event sequencing during the manufacturing process

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Watchdog (to monitor for processes in the system that are out of control)

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RST: reset signal available for the CPU

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Non-volatile RAM (to store startup parameters, ethernet address, etc.)

Most of the members of the TIMEKEEPER family (M48T02, M48T18, M48T58, M48T58Y,

M48T35, M48T35AV, M48T35Y, M48T37V, and M48T37Y) are already being used by

manufacturers of VME (Versa Module Eurocard) boards. However, the ones that are best

suited for new ‘design-in’ boards are the M48T58 and the M48T37Y/V. These have the

following features:

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Automatic chip deselect and write protect when the power fails (as described in

application note AN1012)

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BCD-coded year, month, day, date, hours, minutes, and seconds (as described in

application note AN923)

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Software calibration for increased clock accuracy (as described in application note

AN934)

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8K x 8 non-volatile static RAM (as described in application note AN1012)

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Microprocessor power-on reset (devices with 16-byte register maps, only)

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Battery-low warning software bit (devices with 16-byte register maps, only)

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WDF interrupt function (devices with 16-byte register maps, only)

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Periodic alarms (devices with 16-byte register maps, only)

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Industry’s first fully surface mountable TIMEKEEPER solution (as described in

application note AN1019)

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Industry’s smallest non-volatile TIMEKEEPER footprint (as shown in application note

AN1019)

package: a standard SOIC that is surface mounted in the conventional way, and then is fitted

with a SNAPHAT top, as shown in Figure 2, containing the battery and crystal.

Figure 2.

SOIC and SNAPHAT package

AI02493