Datasheet

35
ATmega8A [DATASHEET]
8159E–AVR–02/2013
details on which pins are enabled. If the input buffer is enabled and the input signal is left floating or have an analog
signal level close to V
CC
/2, the input buffer will use excessive power.
10.8 Register Description
10.8.1 MCUCR – MCU Control Register
The MCU Control Register contains control bits for power management.
• Bit 7 – 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 exe-
cuted. To avoid the MCU entering the sleep mode unless it is the programmer’s purpose, it is recommended to set
the Sleep Enable (SE) bit just before the execution of the SLEEP instruction.
• Bits 6:4 – SM2:0: Sleep Mode Select Bits 2, 1, and 0
These bits select between the five available sleep modes as shown in Table 10-2.
Note: 1. Standby mode is only available with external crystals or resonators.
Bit 76543210
SE SM2 SM1 SM0
ISC11 ISC10 ISC01 ISC00 MCUCR
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000
Table 10-2. Sleep Mode Select
SM2 SM1 SM0 Sleep Mode
000Idle
0 0 1 ADC Noise Reduction
010Power-down
011Power-save
100Reserved
101Reserved
110Standby
(1)