A method of testing pll stability of hdmi through soc

Abstract

The present invention proposes a method for testing the PLL stability of HDMI through the SOC, and the SOC controls the HDMI signal output, including the following steps: S1: obtaining the nominal frequency value of the reference clock crystal of the SOC is A Hz; S2: measuring the reference clock of the SOC The actual frequency value of the crystal is B Hz; S3: Calculate the frequency offset of the SOC reference clock crystal by [(B‑A) / A] to be C PPM; S4: Measure the HDMI signal output by the SOC reference clock crystal after passing through the PLL The actual frequency value of is D Hz; S5: Obtain the nominal output frequency value of the HDMI signal set by the SOC is E Hz; S6: Calculate the frequency offset of the HDMI signal by [(D‑E) / E] to be F PPM; The PLL stability of HDMI can be judged according to the absolute value of the difference between F PPM and C PPM.

Description

technical field [0001] The invention relates to the field of HDMI video, in particular to a method for testing the PLL stability of HDMI through SOC. Background technique [0002] Phase Locked Loop (PLL: Phase Locked Loop) plays a pivotal role in SOC (System On Chip), especially whether the PLL of HDMI (High Definition Multimedia Interface) is stable or not, determines whether the HDMI signal in SOC can be Normal output; the existing technology uses an oscilloscope to measure the jitter of the HDMI output signal. According to the jitter of the HDMI output signal, the PLL stability of the HDMI is obtained. The measurement by the oscilloscope also requires an active probe, the price of the oscilloscope and the active probe Expensive; therefore, there is an urgent need for a simple and low-cost HDMI PLL stability testing method. Contents of the invention [0003] In order to solve the above problems, the present invention proposes a method for testing the stability of PLL of...

AI Technical Summary

Problems solved by technology

[0002] Phase Locked Loop (PLL: Phase Locked Loop) plays a pivotal role in SOC (System On Chip), especially whether the PLL of HDMI (High Definition Multimedia Interface) is stable or not, determines whether the HDMI signal in SOC can be Normal output; the existing technology uses an oscilloscope to measure the jitter of the HDMI output signal. According to the jitter of the HDMI output signal, the PLL stability of the HDMI is obtained. The measurement by the oscilloscope also requires an active probe, the price of the oscilloscope and the active probe Expensive; therefore, there is an urgent need for a simple, low-cost HDMI PLL stability test method

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