Power consumption and wakeup time measurements and results

AN2857

20/31

Doc ID 15241 Rev 3

Figure 6.

External clock setup

Selection between the external clock and the crystal oscillator is made by the external clock

selection (EXTCLK) option bit. Refer to the option byte sections of the STM8S and STM8A

datasheets for more details.

Firmware description for run mode measurements

Power consumption in run mode depends on several factors which are linked more to the

application than to the mode itself. Therefore, it is difficult to give some typical values. For

example, consumption in run mode depends on the code executed and the code placement

in the memory (the latter because of the pipeline and prefetch buffer).

Section 5.1.2: Power consumption results in run mode gives an overview of consumption in

run mode with the code executed from Flash and RAM memory. The code starts with the

MCU configuration (GPIO, PCG, ...). The MCU then enters an endless loop, executing a

sequence of various instructions one hundred times. This is to benefit from the prefetch

buffer.

Note:

The same code is executed from Flash and from RAM memory.

Firmware description for low-power modes measurements

The code starts with the MCU configuration (GPIO, PCG, Flash mode, and regulator used

during the low-power mode). The low-power mode entering instruction is then executed and

the microcontroller switches to the corresponding low-power mode. The measurement is

taken when the MCU is actually in low-power mode.

For more details about firmware configurations please refer to the zip file which contains the

source codes related to this application note.

STM8

OSCIN

ai15049

OSCIN

5 V or 3.3 V

t

0 V