# Basic Low Power Project 1.4

## Purpose

Demonstrates the several low-power modes available on the AT91SAM7L chip family from Atmel.

## Hardware Requirements

This example requires an AT91SAM7L-EK board.

## Description

This example enables the user to select between the different operating modes available on the SAM7L. The SLCD displays the current mode (only briefly in most modes, since the SLCD is disabled to reduce power consumption).

Pressing any key from the first row of the keyboard changes the current mode. Here are the modes from left to right:

- 37 MHz mode: SLCD enabled, SRAM backup disabled, RTC disabled, BOD disabled, PIO interrupt on keyboard pins.
- Backup mode: SLCD disabled, SRAM backup disabled, RTC disabled, BOD disabled, Voltage regulator disabled, wake-up on keyboard pins or FWUP.
- Off mode: chip is shut down entirely, wake-up on FWUP.
- Backup mode 2: SLCD disabled, SRAM backup enabled, RTC enabled, BOD disabled, Voltage regulator disabled, wake-up on keyboard pins, FWUP and automatic wake-up on RTC after 5 seconds.
- Backup mode 3: SLCD enabled, SRAM backup enabled, RTC disabled, BOD enabled (sampling every 32 slow clock ticks), Voltage regulator disabled, wake-up on keyboard pins or FWUP.
- Wait mode: SLCD disabled, SRAM backup disabled, RTC disabled, BOD disabled, PLL & main oscillator disabled, Voltage regulator in deep mode at 1.55V, fast wake-up on keyboard pins.
- Idle mode: SLCD disabled, SRAM backup disabled, RTC disabled, BOD disabled, core runs on slow clock with PLL and main oscillator disabled, voltage regulator in deep mode at 1.55V, processor clock is stopped wake-up on keyboard pins.

## Usage

1. Build the program and download it inside the evaluation board. Please refer to the SAM-BA User Guide, the GNU-Based Software Development application note or to the IAR EWARM User Guide, depending on your chosen solution.
2. Start the application.
3. The SLCD should display the startup mode, which is 37 MHz.
4. Pressing any keys from the first rows will change the mode as described above.

###### Atmel Corporation ©2008