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Hello, everyone, today we're going to learn the chip selection signal

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CS can be understood as chip selection

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When many chips are connected to the same bus,

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a signal is needed to distinguish which chip processes the data and address on the bus

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In this case, a chip selection signal is needed

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The common names of chip selection signals are CS#, CE#

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The chip selection signal usually appears on the SPI bus and is used to read the BIOS

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For example, this U6001, which is a FLASH chip

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The 1st pin of this FLASH ROM is CE#,

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which is the chip selection signal

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When the CPU or EC is reading the data in the FLASH ROM,

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it can measure the chip selection waveform on this first pin

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This waveform is the waveform of the chip selection signal

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There are countless times of pulling down as the waveform

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The EC or CPU is reading the data in the FLASH ROM when we detect this type of chip waveform

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Okay, that's the chip selection signal