AN4635 datasheet(17/34 Pages) STMICROELECTRONICS

Part #	AN4635

Description	Minimization of power consumption using LPUART in microcontrollers of the STM32L0 series

PDF	34 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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DocID027290 Rev 1

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AN4635

Power consumption comparison

6.3

Interrupt operation overhead

The interrupt mechanism on the ARM cortex core is very efficient, but still represents an

additional effort. This fact is best illustrated by comparison on the very minimum core clock

suitable for interrupt driven operation of our example code, 250 kHz.

As shown in Figure 4, the IT code (black line) actually spends almost no time in Sleep mode

(waiting for interrupt) and the power consumption is comparatively high. Blocking operation

represented by the red line saves some energy in waiting for event (Tx buffer empty or Rx

buffer full).

This comparison cannot be absolutely fair, as a different code is executed, nevertheless it

holds significance of code optimization too.

Figure 4. Interrupt operation overhead

ULP/FWU

+/+

Baud rate

9600

SW used

Blocking operation (Com Polling)

with define RXSLEEP

Also TXSLEEP defined

Table 5. Configurations - Sleep mode vs. LPRUN (continued)

Curve in Figure 3

Black

Green

Red

AN4635 Datasheet(PDF) 17 Page - STMicroelectronics