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Hello everyone, today we will learn about the bridge chip and IO standby conditions

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of the domestic computer Loongson mainboard

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Mainly introduces the standby power supply of the bridge chip and the standby conditions of the IO

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This is the mainboard with Loongson CPU

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Its bridge chip standby power supply mainly has two power supplies

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One is called ACPI_3V3, this is its 3.3V main standby power supply

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The measurement point is usually measured at the B10 pin of the PCIE slot

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VDD_RSM is 1.1V main standby power supply,

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this power supply needs to refer to the circuit diagram to measure

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The 1V standby of this mainboard is on the back of the mainboard, which is generated by two voltage regulators.

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Ok, these are the two main and standby power supplies of the Godson bridge

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Next, let's take a look at its IO standby power supply

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The standby power supply of IO usually has this insurance inductor next to the IO

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For example, this FB24, which is an inductor

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We actually measured a 3.269V standby power supply on this inductor

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This is the main power supply for the IO

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With the power supply, its crystal oscillator will start to vibrate

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This is also its standby clock

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Usually there is a 32.768KHz crystal oscillator next to the IO

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Our measured frequency is also about 32.77KHz

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Of course, although the frequencies of the IO and the RTC circuit are the same, their peak values are different.

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The peak value of the RTC circuit is about 600mV,

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but the 32.768KHz peak value of the IO can reach about 3.2V

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They have the same frequency, but different peaks

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Under such working conditions, the measurement point can be found without a circuit diagram

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Part of the IO built-in clock

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The third condition is that its standby reset

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In the absence of a circuit diagram, there is no way to find its measurement point

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After the IO satisfies the standby power supply, clock, and reset,

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the IO needs to read the program to configure its own pins

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Its program is usually placed in a Flash ROM chip next to the EC

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We usually judge whether it reads the program by measuring its SPI bus waveform

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This waveform can be measured during the reading process

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This is the chip select signal waveform measured at its pin 1

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When we measure this waveform, it means that the IO is reading its program

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Ok, this is the bridge chip and IO standby condition