Application Note
7 of 38
001-86233 Rev. *I
2021-11-04
PSoC™ 4 MCU low
-power modes and power reduction techniques
Low-power mode details
3.1.2
Sleep mode transitions
ModusToolbox™
and
PSoC™
Creator supply API functions to enter sleep. These functions configure the device
for sleep. No other API calls are necessary.
ModusToolbox
™ software
–
Sets the system into deep sleep power mode and
calls the registered callback functions. This is a CPU-centric power mode. It means that the CPU has indicated
that it is in sleep mode and its main clock can be removed.
Returns the current sleep status
.
PSoC™
Creator:
CySysPmSleep()
–
Sets the system into deep sleep power mode and calls the registered
callback functions. This is a CPU-centric power mode. It means that the CPU has indicated that it is in sleep
mode and its main clock can be removed.
No return value
.
Exit from sleep mode occurs when an interrupt is triggered. Upon exiting sleep mode, the device re-enters
active mode. The configuration of sleep wakeup sources requires only that their interrupts be enabled.
3.1.3
Sleep mode use cases
Sleep mode should be used when peripherals such as the ADC, CAPSENSE
™
, digital communication, or others
must remain active, but CPU activity is not required. This can reduce current consumption between events
such as ADC conversions and digital communication transactions.
3.2
Deep sleep mode
In deep sleep mode, the high-frequency clocks and peripherals that require high-frequency clocks are disabled.
The high-frequency clocks include the internal main oscillator (IMO), external crystal oscillator (ECO), and
phase-locked loops (PLLs). Note that the ECO and PLLs are not available in all
PSoC™
4 MCU devices.
The internal low-speed oscillator (ILO) clock remains active and can be used to clock the watchdog timer
(WDT), which can be used as a sleep timer to wake the system from deep sleep. Some
PSoC™
4 MCU devices
also include a watch crystal oscillator (WCO) that can operate during deep sleep.
The I
2
C block can continue operating in slave mode to monitor the I
2
C bus, allowing wakeup upon I
2
C address
match.
3.2.1
Deep sleep mode wakeup sources
An I
2
C address match, the WDT, GPIO interrupts, CTB/CTBm comparator interrupts, and low-power comparator
interrupts can wake the device from deep sleep. The WDT block contains multiple counters that can be
configured independently to generate interrupts, resets, or both. This allows the WDT to function as a sleep
timer as well.
3.2.2
Deep sleep mode transitions
ModusToolbox™
software and
PSoC™
Creator supply API functions to enter deep sleep. These functions
configure the device for deep sleep. No other API calls are necessary.
ModusToolbox
™ software
–
Sets the system into deep sleep power mode.
If firmware attempts to enter this mode before the system is ready, the device will go into sleep mode instead
and automatically enter the originally intended mode when the hold-off expires.
Returns the current sleep
status
.
