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Hello everyone, today let's learn about the SPI bus

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SPI bus is a bus consisting of four lines

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Usually used for EC or PCH to read the program in Flash ROM

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These four lines are chip select signal, serial data output, serial data input and serial clock

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These four lines are respectively on the 1st, 2nd, 5th and 6th pin of this 8-pin Flash chip

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Take a look at this pin definition

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The first pin is CS#, which is the chip select signal of the SPI bus

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The second pin is DO, which is the serial data output of the SPI bus

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Pin 5 is the serial data input of the SPI bus

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The 6th pin CLK refers to the serial clock of the SPI bus

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This is the SPI bus

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The other pins of this Flash chip are: Pin 3 WP#, which is the write protection pin of the chip

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Pin 4 GND, this is the ground pin of the chip

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Pin 7 HOLD#, this is the pause and interrupt signal of the chip

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The 8th pin VCC, this is the power supply pin of the chip, the power supply voltage is usually 3.3V or 1.8V

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With the increasing capacity of Flash chips

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Higher and higher requirements for SPI bus transmission speed

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So now there is a SPI bus called 4x speed

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Like this UO2

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It retains the 1st pin CS# (chip select signal) and the 6th pin CLK (serial clock)

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Then redefine the original 5th pin SI (serial data input) signal as IO0

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Redefine pin 2 SO (serial data output) as IO1

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Then define pin 3 WP# (write protection) as IO2

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Redefine pin 7 HOLD# (pause, interrupt) as IO3

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Input and output composed of four lines of IO0, IO1, IO2, and IO3, plus chip select signal and clock

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This is the quad-speed SPI bus

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Its transfer speed is faster than the traditional four-wire SPI bus

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Mainly used to meet large-capacity Flash ROM data transmission

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Whether it's EC or PCH

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It can measure the SPI bus waveform on any line of the SPI bus when reading the Flash ROM

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OK,this is the SPI bus