Answer:
The ADC typically requires a sampling clock to function correctly, as it determines when the ADC takes measurements. However, the ability to configure the ADC over SPI without a sampling clock depends on the specific ADC model and its features. Some ADCs may allow you to configure registers and perform setup tasks without a clock, but the ADC won't perform conversions or output valid data until a clock signal is provided. In some cases, the ADC might have internal clock generation (e.g., an internal oscillator), or the clock could be external. While you may be able to configure the ADC before the clock is active, data conversion will be invalid without the clock. As a best practice, it’s advisable to check for the sampling clock output at the clock-out pin of the ADC using an appropriate instrument.