RV5C339A Datasheet, PDF (46/51 Pages) RICOH electronics devices division – 3-WIRE SERIAL INTERFACE REAL-TIME CLOCK ICs WITH VOLTAGE MONITORING FUNCTION

8. Typical Software-based Operations
8.1 Initialization at Power-on
Start
*¹
Power-on
XSTP=1?
*^{2 NO}
YES
*⁴
Set Oscillation Adjustment Register
and Control Registers 1 and 2, etc.
RV5C339A
*³
NO
VDET=0?
YES
Warning of Backup Battery
Run-down
*1) After power-on from 0 volts, the start of oscillation and the process of internal initialization require a time span on the order of 1 to 2 seconds, so that
access should be done after the lapse of this time span or more.
*2) The XSTP bit setting of 0 in the control register 1 indicates power-on from backup battery and not from 0 volt. The XSTP bit may fail to be set to 1 in the
presence of any excessive chattering in power supply in such events as installing backup battery. Should there be any possibility of this failure occurring,
it is recommended to initialize the RV5C339A regardless of the current XSTP bit setting. For further details, see “3. Oscillation Halt Sensing and Supply
Voltage Monitoring”.
*^{3) This step is not required when the supply voltage monitoring circuit is not used.}
*^{4) This step involves ordinary initialization including the oscillation adjustment register and interrupt cycle settings.}
8.2 Writing of Time and Calendar Data
Wait for 31µs
*¹
Write to Time Counter
and Calendar Counter
*²
*1) This step of waiting is detailed in “1.5 Considerations in Reading
and Writing Time Data”.
*2) Any writing to the second counter will reset divider units lower than
the second digits.
The RV5C339A may also be initialized not at power-on but in the
process of writing time and calender data.
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