What is sleep mode in android? What will happen to CPU once screen (LCD) light goes off?
Sleep mode - is phone switched off. CPU will not work when LCD is turned off.
Sleep mode - means CPU will be sleeping. CPU will not work when LCD is turned off.
Sleep mode - means CPU will be sleeping. CPU will go to sleep mode with in fraction of seconds after LCD is turned off.
Sleep mode - means CPU will be sleeping and will not accept any command except from RIL(Radio Interface Layer) and alarms. CPU will go to sleep mode with in fraction of seconds after LCD is turned off.
There is small difference in power consumption when you compare a phone with laptops.
Laptops most of the times runs on direct power through charger. (Mostly we carry charge with laptop).
Mobiles mostly run on battery power. (Rarely we carry charger with us).
By keeping this in mind, android has designed in a such a way that, phone will not consume battery power if user is not interacting with the phone. This is to increase battery back up time for user.
Thats why when LCD screen power is off (that means user is not interacting with phone), with in fraction of seconds CPU will also go to a mode (sleep mode) where it does minimal work and saves battery power. When CPU is in sleep mode, it accepts commands only from RIL (radio interface layer) which is basically sms and call functions, and alarms. Other than this CPU will stop executing other applications functions.
Note : If any application wants CPU time for its emergency work when CPU is in sleep mode, then it can request CPU time by using WAKE LOCKS.
For eg : MP3 application has to keep playing songs in its service, even though user has turned off LCD screen. That means MP3 application's service has requested CPU time by using WAKE LOCKS.
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