CT, electrical performance, programming, key functions, etc. belong to functional testing. Functional testing refers to the necessary logic or signal state tests under specific working conditions (i.e., the normal use environment of the chip, usually at room temperature) and the normal operation of the chip. According to the original factory specifications and industry standards or specifications, this test designs a feasibility test vector or a special test circuit, applies the corresponding signal source input to the testing chip, analyzes the logical relationship of the signal and the change state of the output waveform through specific conditions such as adjustment and control of the peripheral circuit, signal amplification or conversion matching, and detects the functional characteristics of the chip.