In addition, for UL/IEC 60730-1/60335-1 certification, the ADC module usually needs to be self-tested. An external voltage reference chip like the TLV431 can be added to the peripheral of the C2000 MCU connected to the AD port. A single C2000 integrated circuit usually contains multiple ADC modules, and each ADC module needs to be verified. Therefore, the AD port connected to the voltage reference chip is usually able to be sampled by any ADC module. This signal is sampled during power-on self-checking and periodic self-checking, and is considered passed if the signal falls within a certain deviation range.