Datasheet

ATtiny13

2535E–AVR–10/04

Power Management

and Sleep Modes

The high performance and industry leading code efficiency makes the AVR microcon-

trollers an ideal choice for low power applications.

Sleep modes enable the application to shut down unused modules in the MCU, thereby

saving power. The AVR provides various sleep modes allowing the user to tailor the

power consumption to the application’s requirements.

To enter any of the three sleep modes, the SE bit in MCUCR must be written to logic

one and a SLEEP instruction must be executed. The SM1..0 bits in the MCUCR Regis-

ter select which sleep mode (Idle, ADC Noise Reduction, or Power-down) will be

activated by the SLEEP instruction. See Table 10 for a summary. If an enabled interrupt

occurs while the MCU is in a sleep mode, the MCU wakes up. The MCU is then halted

for four cycles in addition to the start-up time, executes the interrupt routine, and

resumes execution from the instruction following SLEEP. The contents of the Register

File and SRAM are unaltered when the device wakes up from sleep. If a reset occurs

during sleep mode, the MCU wakes up and executes from the Reset Vector.

Figure 11 on page 21 presents the different clock systems in the ATtiny13, and their dis-

tribution. The figure is helpful in selecting an appropriate sleep mode.

MCU Control Register –

MCUCR

The MCU Control Register contains control bits for power management.

• Bit 5 – SE: Sleep Enable

The SE bit must be written to logic one to make the MCU enter the sleep mode when the

SLEEP instruction is executed. To avoid the MCU entering the sleep mode unless it is

the programmer’s purpose, it is recommended to write the Sleep Enable (SE) bit to one

just before the execution of the SLEEP instruction and to clear it immediately after wak-

ing up.

• Bits 4, 3 – SM1..0: Sleep Mode Select Bits 2..0

These bits select between the three available sleep modes as shown in Table 10.

• Bit 2 – Res: Reserved Bit

This bit is a reserved bit in the ATtiny13 and will always read as zero.

Bit 76543210

– PUD SE SM1 SM0 — ISC01 ISC00 MCUCR

Read/Write R R/W R/W R/W R/W R R/W R/W

Initial Value00000000

Table 10. Sleep Mode Select

SM1 SM0 Sleep Mode

00Idle

0 1 ADC Noise Reduction

1 0 Power-down

11Reserved