RV-8523 Datasheet, PDF (29/57 Pages) MICORO CRYSTAL SWITZERLAND – Real Time Clock

Micro Crystal
Real Time Clock / Calendar Module
9.5. ALARM FLAG
Alarm function block diagram:
RV-8523
1) _{Only when all enabled alarm settings are matching. It’s only on increment to a matched case that the alarm flag is set.}
When one or several alarm registers are loaded with a valid minute, hour, day, or weekday value and its
corresponding alarm enable bit (AE_x) is logic 0, then that information is compared with the current minute, hour,
day, and weekday value. When all enabled comparisons first match, the alarm flag, AF (register Control 2), is set
logic 1.
The generation of interrupts from the alarm function is controlled via bit AIE (register Control 1). If bit AIE is
enabled, then the INT_1 pin follows the condition of bit AF. AF remains set until cleared by the interface. Once AF
has been cleared, it will only be set again when the time increments to match the alarm condition once more. Alarm
registers, which have their AE_x bit logic 1 are ignored. The generation of interrupts from the alarm function is
described more detailed in section 9.1.
Next page tables show an example for clearing bit AF. Clearing the flag is made by a write command, therefore bits
2, 1, and 0 must be re-written with their previous values. Repeatedly re-writing these bits has no influence on the
functional behavior.
Alarm flag timing:
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