ST72E331 datasheet(25/107 Pages) STMICROELECTRONICS

25 / 107 page

25/107

ST72E331 ST72T331

POWER SAVING MODES (Cont’d)

4.4.4 Halt Mode

The Halt mode is the MCU lowest power con-

sumption mode. The Halt mode is entered by exe-

cuting the HALT instruction. The internal oscillator

is then turned off, causing all internal processing to

be stopped, including the operation of the on-chip

peripherals. The Halt mode cannot be used when

the watchdog is enabled, if the HALT instruction is

executed while the watchdog system is enabled, a

watchdog reset is generated thus resetting the en-

tire MCU.

When entering Halt mode, the I bit in the CC Reg-

ister is cleared so as to enable External Interrupts.

If an interrupt occurs, the CPU becomes active.

The MCU can exit the Halt mode upon reception of

an interrupt or a reset. Refer to the Interrupt Map-

ping Table. The oscillator is then turned on and a

stabilization time is provided before releasing CPU

operation. The stabilization time is 4096 CPU clock

cycles.

After the start up delay, the CPU continues oper-

ation by servicing the interrupt which wakes it up or

by fetching the reset vector if a reset wakes it up.

Figure 19. HALT Flow Chart

EXTERNAL

INTERRUPT1)

RESET

HALT INSTRUCTION

4096 CPU CLOCK

FETCH RESET VECTOR

OR SERVICE INTERRUPT

CYCLES DELAY

CPU CLOCK

OSCILLATOR

PERIPH. CLOCK2)

I-BIT

OFF

SET

CPU CLOCK

OSCILLATOR

PERIPH. CLOCK

I-BIT

OFF

CLEARED

OFF

WDG

ENABLED?

RESET

WATCHDOG

1) or some specific interrupts

Note: Before servicing an interrupt, the CC register is

pushed on the stack. The I-Bit is set during the inter-

rupt routine and cleared when the CC register is

popped.

CPU CLOCK

OSCILLATOR

PERIPH. CLOCK

I-BIT

SET

2) if reset PERIPH. CLOCK = ON ; if interrupt

PERIPH. CLOCK = OFF

ST72E331 数据表(PDF) 25 Page - STMicroelectronics

ST72E331 数据表(HTML) 25 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载

链接网址

ST72E331 数据表(PDF) 25 Page - STMicroelectronics

ST72E331 数据表(HTML) 25 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表 下载

链接网址

数据表下载