Backup And Recovery - Epson RA8804 CE Applications Manual

RA8804 CE

8.11. Backup and Recovery


This circuit is sensitive to power supply noise and supply voltage should be stabilized to avoid negative
impact on the accuracy.

tR1 is needed for a proper power-on reset. If this power-on condition cannot be kept, it is necessary to
send an initialization routine to the RTC by software.

In case of repeated ON/OFF of the power supply within short term, it is possible that the power-on reset
becomes unstable.

After power-OFF, keep VDD = GND for more than 10 seconds for a proper power-on reset.
When it is impossible, please initialize the RTC by the software.

As for the communication of I2C, completion of less than 1 second is recommended.

If such communication requires 2 seconds (Max.) or longer, the I2C bus interface is reset by the internal
bus timeout function.

When bus-time-out occur, SDA turns to Hi-Z input mode.

But readout data of a clock is stable anytime, and there isn't contradiction.
And it does not occur that data of a clock delay even if access time is prolonged.
tR1
VDET
0V
I2C-BUS Communication state
Non-Communication
Item
Power supply rise time1
Access wait time
(After initial power on)
Power supply fall time
Power supply rise time2
Setup time from
Finish of I2C.
*：tR2 is specifications for an oscillation not to stop. Some clocks are not output by an FOUT terminal.
VDD
tCL
Communication
Symbol Condition
tR1 VDD = VSS to 5.5 V
tCL After VDD = VDET
tF VDD = 5.5 V to VDET
 VDD = VDET to 5.5 V
tR2
Before VDD = VDET 
tCD
tF
tCD
Back-up operation
Non-Communication
Min. Typ.
1
30
100
15
0
Page - 35
*
tR2
Max. Unit.
- 10 ms/V
- - ms
- - µs/V
- - µs/V
- - µs
ETM60E-02