DocID17035 Rev 3

15/25

AN3147

Run and low power modes

24

Figure 2. STM8L and STM8AL architecture

4.6

Wait mode

The STM8L and STM8AL devices support two different Wait modes: WFI (Wait for interrupt)

and WFE (Wait for event). Both modes are designed to reduce STM8L and STM8AL device

power consumption by switching off the core when it is not used. Wait mode is mainly used

when the STM8L/STM8AL is waiting for an external or internal event so that the program

execution can continue.

The device can be switched to Wait mode instead of waiting for an Event in Run mode with:

While( ! Event );

This mode can be used with PCG and with a low speed clock source to further reduce the

power consumption of the device.

This mode offers the lowest wakeup time.

4.6.1

Entering Wait mode

Wait mode is entered by executing the WFI or WFE assembly instruction. This stops the

CPU, but other peripherals and the interrupt controller can continue to run. When entering

Wait mode, the global interrupts are automatically enabled.



Before entering WFI mode, at least one interrupt must be enabled.



Before entering WFE mode, at least one event source must be enabled.

D-Bus

Memory

Controller

Instruction

Memory

&

Data E

2

RAM

ITC

Debug

SWIM

STM8

CORE

32-bit

Peripherals

Interrupt

DMA

SWIM protocol

I-Bus

ai17845

8-bit

8-bit

8-bit

Interrupt control