STR750F datasheet(7/73 Pages) STMICROELECTRONICS

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STR750F

Introduction

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Low Power modes

The STR750F supports 5 low power modes, SLOW, PCG, WFI, STOP and STANDBY.

●

SLOW MODE: the system clock speed is reduced. Alternatively, the PLL and the main

oscillator can be stopped and the device is driven by a low power clock (fRTC). The

clock is either an external 32.768 kHz oscillator or the internal low power RC oscillator.

●

PCG MODE (Peripheral Clock Gating MODE): When the peripherals are not used, their

APB clocks are gated to optimize the power consumption.

●

WFI MODE (Wait For Interrupts): only the CPU clock is stopped, all peripherals

continue to work and can wake-up the CPU when IRQs occur.

●

STOP MODE: all clocks/peripherals are disabled. It is also possible to disable the

oscillators and the Main Voltage Regulator (In this case the VCORE is entirely powered

by V18_BKP). This mode is intended to achieve the lowest power consumption with

SRAM and registers contents retained. The system can be woken up by any of the

external interrupts / wake-up lines or by the RTC timer which can optionally be kept

running. The RTC can be clocked either by the 32.768 kHz Crystal or the Low Power

RC Oscillator.

Alternatively, STOP mode gives flexibility to keep the either main oscillator, or the Flash

or the Main Voltage Regulator enabled when a fast start after wake-up is preferred (at

the cost of some extra power consumption).

●

STANDBY MODE: This mode (only available in single supply power schemes) is

intended to achieve the lowest power consumption even when the temperature is

increasing. The digital power supply (VCORE) is completely removed (no leakage even

at high ambient temperature). SRAM and all register contents are lost. Only the RTC

remains powered by V18_BKP. The STR750F can be switched back from STANDBY to

RUN mode by a trigger event on the WKP_STDBY pin or an alarm timeout on the RTC

counter.

Caution:

It is important to bear in mind that it is forbidden to remove power from the VDD_IO power

supply in any of the Low Power Modes (even in STANDBY MODE).

DMA

The flexible 4-channel general-purpose DMA is able to manage memory to memory,

peripheral to memory and memory to peripheral transfers. The DMA controller supports

circular buffer management avoiding the generation of interrupts when the controller

reaches the end of the buffer.

The DMA can be used with the main peripherals: UART0, SSP0, Motor control PWM timer

(PWM), standard timer TIM0 and ADC.

RTC (Real Time Clock)

The real time clock provides a set of continuously running counters which can be used with

suitable software to provide a clock calendar function, and provides an alarm interrupt and a

periodic interrupt. It is clocked by an external 32.768 kHz oscillator or the internal low power

RC oscillator. The RC has a typical frequency of 300 kHz and can be calibrated.

WDG (Watchdog Timer)

The watchdog timer is based on a 16-bit downcounter and 8-bit prescaler. It can be used as

watchdog to reset the device when a problem occurs, or as free running timer for application

time out management.

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