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RX − 8564 LC
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ETM12E-01
13.1.3. Clock counter ( Reg − 02 [h] to 04 [h] )
Address [h]
Function bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
02 Seconds VL 40 20 10 8 4 2 1
03 Minutes
×
40 20 10 8 4 2 1
04 Hours
× ×
20 10 8 4 2 1
• The clock counter counts seconds, minutes, and hours.
• The data format is BCD format
.
For example, when the "seconds" register value is "0101 1001" it indicates 59
seconds.
∗ When overwriting time data, we recommend setting "1" to the STOP bit to stop the clock before overwriting. (This
prevents unintentional carry operations from occurring while overwriting data.)
∗ Note with caution that writing non-existent time data may interfere with normal operation of the clock counter.
1) [
Seconds
] register ( Reg − 02 [h] )
This counter counts seconds.
Count values are updated as: 00 seconds, 01 second, 02 to 59 seconds, 00 seconds, 01 second, etc. in
that order.
2) [
Minutes
] register ( Reg − 03 [h] )
This counter counts minutes.
Count values are updated as: 00 minutes, 01 minute, 02 to 59 minutes, 00 minutes, 01 minute, etc. in that
order.
3) [
Hours
] register ( Reg − 04 [h] )
The [Hours] counter uses a 24-hour clock.
Count values are updated as: 00 hours, 01 hour, 02 to 23 hours, 00 hours, 01 hour, etc. in that order.
4) VL bit ( Voltage Low Flag )
This is a flag bit that retains the result when detecting low voltage.
When the power source's voltage drops below VLOW[V]*, this flag is set to 1.
If this bit's value is "1" when read, this RTC's data is ignored, in which case all registers should be initialized
before being used.
(1) A "1" is set to this VL flag during initial power-on (from 0 V).
Since the value of other registers is undefined at this time, be sure to reset all registers before using
them.
(2) When recovering from backup mode, read this VL flag, and if its value is "1" be sure to initialize the
registers before using them.
(3) When initializing, be sure to clear this VL flag to zero to prepare for the next voltage detection.
(4) This VL flag was designed to provide a voltage drop warning after the voltage of the backup battery or
other devices has gradually dropped, and it is not designed to respond to sharp fluctuations in voltage
due to power supply chatter, etc.
V
LOW
GND
V
DD
(1) VL= ” 1 ” (2) VL= ” 0 ” (3) VL= ” 1 ”
(1) VL="1" as result of initial supply of power
(2) When the power supply is low but voltage not dropping to V
LOW
, VL remains at "0"
with no change
(3) When the power supply is low and voltage dropping below V
LOW
, VL becomes "1".
∗
The value of the VL bit in (2) and (3) need to be zero cleared in (1).
GND=0 V
(5) This VL flag is cleared via a write operation regardless of data.
Be sure to read this flag's value before writing to this register.