The ADS8555 ADC uses SPI serial communication in mode 1 (CPOL = 0 and CPHA= 1). Because the serial clock (SCLK) frequency can be as fast as 36 MHz, the ADS8555EVM offers 47-Ω resistors between the controller and device to aid with signal integrity. Typically, in high-speed SPI communication, fast signal edges can cause overshoot; these 47-Ω resistors slow down the signal edges in order to minimize signal overshoot.