ST7LITEU09 datasheet(40/115 Pages) STMICROELECTRONICS

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POWER SAVING MODES (Cont’d)

9.3 WAIT MODE

WAIT mode places the MCU in a low power con-

sumption mode by stopping the CPU.

This power saving mode is selected by calling the

‘WFI’ instruction.

All peripherals remain active. During WAIT mode,

the I bit of the CC register is cleared, to enable all

interrupts. All other registers and memory remain

unchanged. The MCU remains in WAIT mode until

an interrupt or RESET occurs, whereupon the Pro-

gram Counter branches to the starting address of

the interrupt or Reset service routine.

The MCU will remain in WAIT mode until a Reset

or an Interrupt occurs, causing it to wake up.

Refer to Figure 24.

Figure 24. WAIT Mode Flow-chart

Note:

1. Before servicing an interrupt, the CC register is

pushed on the stack. The I bit of the CC register is

set during the interrupt routine and cleared when

the CC register is popped.

WFI INSTRUCTION

RESET

INTERRUPT

CPU

OSCILLATOR

PERIPHERALS

IBIT

OFF

FETCH RESET VECTOR

OR SERVICE INTERRUPT

CPU

OSCILLATOR

PERIPHERALS

IBIT

OFF

CPU

OSCILLATOR

PERIPHERALS

IBIT

X 1)

256 OR 512 CPU CLOCK

DELAY

CYCLE

ST7LITEU09 Datasheet(PDF) 40 Page - STMicroelectronics

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