ST6208LD3SLASHOTP datasheet(34/104 Pages) STMICROELECTRONICS

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6.3 STOP MODE

STOP mode is the lowest power consumption

mode of the MCU (see Figure 22).

The MCU goes into STOP mode as soon as the

STOP instruction is executed. This has the follow-

ing effects:

– Program execution is stopped, the microcontrol-

ler can be considered as being “frozen”.

– The contents of RAM and the peripheral regis-

ters are kept safely as long as the power supply

voltage is higher than the RAM retention voltage.

– The oscillator is stopped, so peripherals cannot

work except the those that can be driven by an

external clock.

Exit from STOP Mode

The MCU remains in STOP mode until one of the

following events occurs:

– RESET (Watchdog, LVD or RESET pin)

– A peripheral interrupt (assuming this peripheral

can be driven by an external clock)

– An external interrupt (I/O port, NMI)

In all cases a delay of 2048 clock cycles (f

INT) is

generated to make sure the oscillator has started

properly.

The Program Counter then points to the starting

address of the interrupt or RESET service routine

(see Figure 21).

STOP Mode and Watchdog

When the Watchdog is active (hardware or soft-

ware activation), the STOP instruction is disabled

and a WAIT instruction will be executed in its place

unless the EXCTNL option bit is set to 1 in the op-

tion bytes and a a high level is present on the NMI

pin. In this case, the STOP instruction will be exe-

cuted and the Watchdog will be frozen.

Figure 21. STOP Mode Timing Overview

STOP

RUN

2048

RESET

INTERRUPT

STOP

INSTRUCTION

FETCH

VECTOR

CYCLE

CLOCK

DELAY

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