CHAPTER 7-2: VBAT Domain(A)
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 275
5. Procedure for Setting 32 kHz Clock
This section explains recommended sequences of setting the 32 kHz oscillation circuit when using the
RTC.
Features of 32 kHz Oscillation Circuit in VBAT Domain
With the 32 kHz oscillation circuit incorporated in the VBAT Domain, even when the CPU Domain and the
Always-on Domain are turned off, the 32 kHz oscillation circuit can continue operating and the RTC can
continue counting the time.
Linking with Clock Control Circuit
If the 32 kHz oscillation circuit in the VBAT Domain is linked with the clock control circuit is executed, the
VBAT Domain becomes compatible with the FM3 Family.
In addition, with the 32 kHz oscillation circuit in the VBAT Domain linked with the clock control circuit and
the VCC power supply turned off, if the CPU transits to deep standby mode or deep standby stop mode
as the VCC power supply is turned on, the 32 kHz oscillation automatically stops.
If the 32 kHz clock is only used as the clock for subrun mode, power consumption of the backup power
supply can be reduced by linking the 32 kHz oscillation circuit with the clock control circuit.
Example of setting procedure
(1) Set VBAT I/O Port to use the 32k oscillation circuit.
(2) Set an appropriate current value for the current that is to flow to the oscillation amplifier circuit.
(3) Set the oscillation boost time.
(4) Enable the cooperative operation with the clock control circuit.
In addition, enable the oscillation.
To Next Page
Loading...
