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(3) The IC determines whether power has been lost based on whether there is an AC input to the 50/60 Hz INPUT pin.
• Determining that power has been lost
When the AC input falls under 1 Hz, the IC determines that power has been lost and stops display output.
However, this determination is performed by comparing that input with the frequency from the RC oscillator on
the CR OSC pin. If the CR OSC pin is not used, the IC will not check for power outages.
Note that a high level should be applied to the CR OSC pin if it is not used.
• Power outage operation
If a backup oscillator is connected to the CR OSC pin, at the point that a power outage is detected LED segment
output and RADIO OUTPUT pin output are stopped. Also, if an alarm has been interrupted by the snooze function,
the snooze function is cleared and the alarm output restarted. At this point the clock operation will continue using
the backup oscillator.
During a power outage, only the OFF input (a low level to the MANUAL & SLEEP pin) is valid, and all other
operation inputs are disabled.
During the backup state following a power outage detection, at the point that the AC input is restored to a
frequency over 1 Hz the IC switches from operation based on the RC oscillator to operation based on AC input.
The display indicates a power outage by displaying the current time flashing at 1 Hz. However, alarm indicators
for enabled alarms will be lit and not flashing. Apply a high or low level to the TIME SET INPUT pin to stop the
flashing and return to normal display.
Note that if the conditions for an alarm are fulfilled, that alarm will be output even during a power outage.
If a backup oscillator is not connected to the CR OSC pin, all operations will halt. That is, power outage detection
and backup operation are not performed. Also, the following operations will be performed after recovery from a
power outage.
— If the rated power supply voltage (4.0 to 6.0 V) was maintained:
Clock operation restarts from the point power was lost.
— If the power supply voltage fell below the rated voltage:
The IC returns to the initial start state.
• Current time during a power outage
The current time is maintained during a power outage using a clock signal generated by dividing the oscillation
frequency of the RC oscillator circuit. The standard oscillation frequency of the RC oscillator circuit is 4800 Hz.
When the mode is set to 50 Hz mode, the 4800 Hz signal is divided by 96 to form a 50 Hz signal, and when set to
60 Hz mode, the 4800 Hz signal is divided by 80 to form a 60 Hz signal.
Colon
(1) Remains lit during normal operation.
(2) Flashes at 1 Hz following a initial reset, following recovery from a power outage, and during time setting modes for
the current time, alarm A, and alarm B.
(3) Turns off during calendar display and the "On" and sleep time displays.
LC85632
No. 4659-29/34
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