Idle mode vs Sleep mode

Hi
What is the diffrent between Idle mode and Sleep mode?

ex:
IDLEN: Idle Enable bit
1 = Device enters Idle mode on SLEEP instruction
0 = Device enters Sleep mode on SLEEP instruction

The difference would be the amount of power the chip uses. In idle mode, the IC is still on but is not executing any instructions. In sleep mode, the IC basicaly shuts itself down by turning off the clock as well as all instruction execution. It can only be brought out of sleep mode by a WDT interupt or another external interupt.

Many peripherals also have a bit to disable the peripheral in idle mode. For example, lets say that you want to conserve power but need to listen for incoming bytes on the UART. If your device is using a few timers, some PWM, and SPI, you would configure those peripherals to be disabled in idle mode but keep the UART running. Shutting down those peripherals would save power.

If you go to sleep, pretty much everything is shut down except for the watchdog timer and external interrupts.