RX8111CE
Page
−
12
ETM61E-01
10.2. The behavior and operation restriction at power-ON in RTC
Because most of the RTC registers are synchronized with the oscillation clock of the built-in crystal oscillator, the RTC does not
work normally without the integrated oscillator stabilized. Please initialize the RTC at the time the power supply voltage returns
(VLF = 1) after the oscillation is stabilized (after oscillation start time t
STA
).
If intending to access the RTC after the main supply voltage returns, please note the following points:
1) Please begin to read VLFbit first.
2) When VLF
returns “1”, please initialize all registers. Please perform initial setting only t
STA
(Oscillation start time), when the built-
in oscillation is stable.
3) Access is prohibited within 40 ms the supply voltage exceeds min. V
CLK
(Clock supply voltage (V
DD
> 1.6 V)).
VDD
VDD detect voltage.
+V
DET1
Internal oscillation
Illustration.
t
STA
Oscillation start time.
0.3 s Typ.
•
Access is enabled
•
Normal operation start
Minimum voltage of keeping time and date.
V
CLK
.
During power-on initialization or power supply
voltage recovery after drop in clock maintenance
voltage
40
ms
After 40 ms progress, Confirm a state by VLF-bit
At the time of VLF=1: After a t
STA
wait, initial setting is necessary.
At the time of VLF=0: Register access is possible.
VOUT
FOUT
Figure 15 Oscillation start time chart (Power initial supply)
•
Recovery from Backup
V
OUT
V
DD
V
DD
detect vV
DET1
Minimum voltage of keeping time and date.
V
CLK
.
Recovery from Backup
After 40 ms progress, access is enabled.
After VLF confirmation, it is similar
to initial power ON.
FOUT
40 ms
Figure 16 Oscillation start time chart (Backup resume)
