ST7LITE49K2 datasheet(66/245 Pages) STMICROELECTRONICS

66 / 245 page

Power saving modes

ST7LITE49K2

66/245

9.4.1

Active-halt mode

Active-Halt mode is the lowest power consumption mode of the MCU with a real-time clock

available. It is entered by executing the ‘HALT’ instruction when Active-halt mode is enabled.

The MCU can exit Active-Halt mode on reception of a Lite timer/ AT timer interrupt or a

Reset.

●

When exiting Active-Halt mode by means of a Reset, a 256 CPU cycle delay occurs.

After the start up delay, the CPU resumes operation by fetching the Reset vector which

woke it up (see Figure 28).

●

When exiting Active-Halt mode by means of an interrupt, the CPU immediately

resumes operation by servicing the interrupt vector which woke it up (see Figure 28).

When entering Active-Halt mode, the I bit in the CC register is cleared to enable interrupts.

Therefore, if an interrupt is pending, the MCU wakes up immediately.

In Active-Halt mode, only the main oscillator and the selected timer counter (LT/AT) are

running to keep a wakeup time base. All other peripherals are not clocked except those

which get their clock supply from another clock generator (such as external or auxiliary

oscillator).

Caution:

As soon as Active-Halt is enabled, executing a HALT instruction while the Watchdog is

active does not generate a Reset if the WDGHALT bit is reset.

This means that the device cannot spend more than a defined delay in this power saving

mode.

Figure 27.

Active-halt timing overview

This delay occurs only if the MCU exits Active-Halt mode by means of a RESET.

HALT

RUN

256 CPU

CYCLE DELAY 1)

RESET

INTERRUPT

HALT

INSTRUCTION

FETCH

VECTOR

ACTIVE

[Active-halt Enabled]

ST7LITE49K2 数据表(PDF) 66 Page - STMicroelectronics

ST7LITE49K2 数据表(HTML) 66 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