Cypress FM4 Series - Page 210

CHAPTER 6: Low Power Consumption Mode
210 FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E
Return from RTC Mode
The CPU returns from RTC mode in one of the following situations.
 Return due to reset
If a reset (INITX pin input reset or low voltage detection reset) occurs, the CPU switches to high speed
CR run mode regardless of the clock mode.
In RTC mode, since the software watchdog reset, the hardware watchdog reset, the clock supervisor
reset and the anomalous frequency detection reset are not available, these resets cannot be used to
make the CPU return from RTC mode.
 Return due to interrupt
On receiving a request for an effective interrupt, which can be an NMI interrupt, an external interrupt, a
USB wakeup interrupt, an RTC interrupt, a HDMI-CEC/Remote Control Reception interrupt or a low
voltage detection interrupt, in RTC mode, the CPU returns from RTC mode and transits to a Run mode
corresponding to the clock mode indicated in the RCM[2:0] bits in the System Clock Mode Status
Register (SCM_STR)
Table 3-7 Operation Mode after Return from RTC Mode due to Interrupt
Status of Master Clock before Transition to RTC Mode
RCM = 000
(High Speed CR
Oscillator)
RCM = 001
(Main Oscillator)
RCM = 010
(PLL Oscillator)
RCM = 100
(Low Speed CR
Oscillator)
RCM = 101
(Sub Oscillator)
Operation mode after
return due to interrupt
High speed CR
run mode
Main run mode
PLL run mode
Low speed CR run
mode
Sub run mode
 Oscillation stabilization wait at return
On returning from RTC mode due to a reset, the CPU waits for the stabilization of high speed CR clock
oscillation and that of low speed CR clock oscillation. If the CPU returns from RTC mode due to an
interrupt, the oscillation stabilization wait changes according to the master clock that had been used
before the CPU transited to RTC mode. Table 3-8 shows the relationship between the oscillation
stabilization wait and the master clock.
Table 3-8 Oscillation Stabilization Wait at Return from RTC Mode due to Interrupt
Status of Master Clock before Transition to RTC Mode
RCM = 000
(High Speed CR
Oscillator)
RCM = 001
(Main Oscillator)
RCM = 010
(PLL Oscillator)
RCM = 100
(Low Speed CR
Oscillator)
RCM = 101
(Sub Oscillator)
Oscillation stabilization wait at
return due to interrupt
High speed
CR clock
Yes
No
Main clock
MOSCE = 0 : No
MOSCE = 1 : Yes
Yes
PINC = 0 : Yes
PINC = 1 : No
No
Main PLL
clock
No
PLLE = 0 : No
PLLE = 1 : Yes
Yes
No
Low speed CR
clock
Yes
Yes
Yes
Yes
Yes
Sub clock
No
No
No
No
No