ST72F324J2TCRE View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

ST72F324J2TCRE

8-bit MCU for automotive, 3.8 to 5.5V operating range with 8 to 32 Kbyte Flash, 10-bit ADC, 4 timers, SPI, SCI

STMicroelectronics 

ST72324xx-Auto

8

Power saving modes

Power saving modes

8.1

Introduction

To give a large measure of flexibility to the application in terms of power consumption, four

main power saving modes are implemented in the ST7 (see Figure 21): Slow, Wait (Slow

Wait), Active Halt and Halt.

After a reset the normal operating mode is selected by default (Run mode). This mode

drives the device (CPU and embedded peripherals) by means of a master clock which is

based on the main oscillator frequency divided or multiplied by 2 (fOSC2).

Obsolete Product(s) - Obsolete Product(s) 8.2

From Run mode, the different power saving modes may be selected by setting the relevant

register bits or by calling the specific ST7 software instruction whose action depends on the

oscillator status.

Figure 21. Power saving mode transitions

High

Run

Slow

Wait

Slow Wait

Active Halt

Halt

Low

Power consumption

Slow mode

This mode has two targets:

● To reduce power consumption by decreasing the internal clock speed in the device

● To adapt the internal clock frequency (fCPU) to the available supply voltage

Slow mode is controlled by three bits in the MCCSR register: the SMS bit which enables or

disables Slow mode and two CPx bits which select the internal slow frequency (fCPU).

In this mode, the master clock frequency (fOSC2) can be divided by 2, 4, 8 or 16. The CPU

and peripherals are clocked at this lower frequency (fCPU).

Note:

Slow Wait mode is activated when entering the Wait mode while the device is already in

Slow mode.

Doc ID 13841 Rev 1

53/193

Share Link: