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This lesson is about the working conditions of the SIM card

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and the description of the SIM card in the circuit diagram

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First look at the working conditions of the SIM card

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The SIM card generally has the following working conditions

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First, the detection signal

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This detection signal is also called the card insertion detection signal

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It usually has a pull-up circuit externally, and the power supply is generally 1.8 volts

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Second, power supply

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This power supply usually comes from the NFC chip, usually 1.8 volts

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The third operating condition is the clock signal

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The clock signal is output to the SIM card by the baseband CPU or large CPU

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The fourth working condition is the reset signal

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The reset signal is sent to the SIM card by the baseband CPU or large CPU

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The fifth working condition is the data line, DATA or DA

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It is represented by IO in some drawings

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The data line is used for the baseband CPU or large CPU to read the information of the SIM card

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These are the working conditions of the SIM card

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Next, look at the description of the SIM card in the circuit drawing

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This is a dual card SIM card circuit

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In this circuit, J6300 is the SIM card seat

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NFC_SIMVCC1, NFC_SIMVCC2, they are power supply,

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one is the power supply of card 1, and the other is the power supply of card 2

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This is the reset signal of SIM card 1

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The following is the reset signal of SIM card 2

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Looking further down, CLK is the clock signal of the SIM card

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This is NFC_SWIO, also called VPP, it is also usually called programming power supply

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If this line is not short-circuited, we usually don't consider it

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Further down this is DATA, the data of the SIM card

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The following PRESENT is the card insertion detection signal

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We can see that no matter it is the reset signal, clock signal, power supply and data,

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including the card insertion detection signal,

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a 100-ohm resistor is connected in series to the card seat

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During maintenance, if the ground value cannot be measured at the left end of the resistor,

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but the ground value can be measured at the right end, it means that the resistor is damaged

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If the resistor is damaged, it can be replaced directly

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You can also short both ends of the pads if you can't find a resistor that has the same resistance

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This is the description of the SIM card in the circuit diagram

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That's all for this lesson