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In this lesson, we will talk about the framework of the startup operation process,

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that is, the structure of the startup operation process

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Let's take a look

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The power supply outputs power to the hard disk

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For example,

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the hard disk has a 3V power supply and a 1.8V power supply

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Then the power supply outputs power to the CPU,

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the temporary storage on the CPU circuit, or to the CPU baseband

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Some CPUs have a baseband integrated in them

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BB is the code name here

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VCORE is the core power supply of the CPU,

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VGPU refers to the power supply for the GPU,

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VMODEM refers to the power supply for the baseband

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At the same time,

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it will also supply power to the application circuit and other chips, usually 1-3V

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After the power supply is supplied to the hard disk,

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CPU, and the temporary storage,

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then, the clock circuit composed of the crystal oscillator and the power supply chip

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will provide a clock signal to the CPU circuit,

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which is originally working on standby

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The CPU will also send a clock signal to the hard disk at this time

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And then the power supply will send a reset signal to the CPU

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The CPU will also reset the font library

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At this time, the CPU works,

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reads the boot program in the hard disk through data communication to perform self-test,

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and the CPU performs self-test on itself, temporary storage, and hard disk

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After the self-test is OK,

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it continues to load the boot program

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The CPU needs to output a hold signal to the power supply,

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PS_HOLD is the hold signal

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The power supply will continue to output power and maintain a normal power-on state

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Well, this is the complete startup process of the phone

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We will use this process when repairing the no-booting failure

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As a whole, this process is sequential

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For example, the first step is the battery,

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and the second step is the charging chip

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If there is no problem, it will output the main power supply

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The third step, the clock circuit is running in standby mode,

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The power supply gives a voltage of 1.8V to the power-on signal line

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Next, let's pull down the power-on signal

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It outputs the power supply of the hard disk,

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the power supply of the CPU,

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and the power supply of the temporary storage

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The power chip sends the clock signal to the CPU,

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and then to the hard disk

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Then, the power supply sends a reset signal to the CPU,

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and the CPU resets the hard disk

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After the reset is obtained, the CPU will start a self-test

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What does it read the boot program through?

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It reads the boot program by sending and receiving data

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If there is no problem with the self-test,

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it will output a hold signal, PS_HOLD

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At this point, its loading and booting program is basically completed

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This is the framework of the startup operation

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Okay, that's it for this lesson