Power-save mode, Standby mode, Extended standby mode – Rainbow Electronics ATmega162V User Manual

Page 43: Atmega162/v

ATmega162/V

2513E–AVR–09/03

Power-save Mode

When the SM2..0 bits are written to 011, the SLEEP instruction makes the MCU enter
Power-save mode. This mode is identical to Power-down, with one exception:

If Timer/Counter2 is clocked asynchronously, i.e., the AS2 bit in ASSR is set,
Timer/Counter2 will run during sleep. The device can wake up from either Timer Over-
fl o w o r O u t p u t C o m p a re e v e n t fr o m T i m e r /C o u n t e r 2 if t h e c o r r e s p o n d i n g
Timer/Counter2 interrupt enable bits are set in TIMSK, and the Global Interrupt Enable
bit in SREG is set.

If the Asynchronous Timer is NOT clocked asynchronously, Power-down mode is rec-
ommended instead of Power-save mode because the contents of the registers in the
Asynchronous Timer should be considered undefined after wake-up in Power-save
mode if AS2 is 0.

This sleep mode basically halts all clocks except clk

ASY

, allowing operation only of asyn-

chronous modules, including Timer/Counter 2 if clocked asynchronously.

Standby Mode

When the SM2..0 bits are 110 and an external crystal/resonator clock option is selected,
the SLEEP instruction makes the MCU enter Standby mode. This mode is identical to
Power-down with the exception that the main Oscillator is kept running. From Standby
mode, the device wakes up in six clock cycles.

Extended Standby Mode

When the SM2..0 bits are 111 and an external crystal/resonator clock option is selected,
the SLEEP instruction makes the MCU enter Extended Standby mode. This mode is
identical to Power-save mode with the exception that the main Oscillator is kept running.
From Extended Standby mode, the device wakes up in six clock cycles.

Notes:

1. External Crystal or resonator selected as clock source
2. If AS

bit in ASSR is set

3. For INT1 and INT0, only level interrupt

Table 17. Active Clock domains and Wake up sources in the different sleep modes

Active Clock domains

Oscillators

Wake-up Sources

Sleep Mode

clk

CPU

clk