ST7232A datasheet(36/154 Pages) STMICROELECTRONICS

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ST7232A

36/154

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’ instruction.

All peripherals remain active. During WAIT mode,

the I[1:0] bits of the CC register are forced to ‘10’,

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 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 21.

Figure 21. WAIT Mode Flow-chart

Note:

1. Before servicing an interrupt, the CC register is

pushed on the stack. The I[1:0] bits of the CC reg-

ister are set to the current software priority level of

the interrupt routine and recovered when the CC

WFI INSTRUCTION

RESET

INTERRUPT

CPU

OSCILLATOR

PERIPHERALS

I[1:0] BITS

OFF

FETCH RESET VECTOR

OR SERVICE INTERRUPT

CPU

OSCILLATOR

PERIPHERALS

I[1:0] BITS

OFF

CPU

OSCILLATOR

PERIPHERALS

I[1:0] BITS

XX 1)

256 OR 4096 CPU CLOCK

CYCLE DELAY

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