Managing the Power Consumption of End Devices
In situations where battery power is insufficient for operating an end device continuously, we need to save power at the expense of operational functionality (that is, we need to put the device to sleep). There are different types of sleep modes. For example, in an idle state, the device is operating, but not reading sensors, sending data, or conducting any other activity. In deep sleep, most of the device functions are disabled, which allows it to save the most energy possible–without actually shutting down.
An example of a computer in an idle state can be as simple as a laptop display turning off after a configurable amount of time. Before the display can be used again, an interrupt must be performed by pressing a key, opening the lid, or clicking the mouse before the processor sends a “wake-up” command to the display. Chances are, the processor itself was also in a sleep mode to increase energy savings and component lifetime.
In contrast, if your computer goes into deep sleep mode, it may also switch off the random access memory (RAM). To prevent data loss, it is necessary to store the most recent RAM state to non-volatile memory, such as flash memory, before the computer goes to sleep.