ST72104G datasheet(28/135 Pages) STMICROELECTRONICS

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ST72104G, ST72215G, ST72216G, ST72254G

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POWER SAVING MODES (Cont’d)

8.3 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” ST7 software instruction.

All peripherals remain active. During WAIT mode,

the I bit of the CC register is forced to 0, to enable

all interrupts. All other registers and memory re-

main unchanged. The MCU remains in WAIT

mode until an interrupt or Reset occurs, whereup-

on the Program 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 18.

Figure 18. 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

I BIT

X 1)

4096 CPU CLOCK CYCLE

DELAY

ST72104G Datasheet(PDF) 28 Page - STMicroelectronics

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