47K pull-up resistor is required on pin 38 of EZ-Host

Question: Why is a pull-up resistor required on EZ-Host's A15 (pin 38)?

 

Answer:

EZ-Host requires a 47K pull-up resistor tied to VCC on pin 38. Pin 38 is used as a CLKSEL (clock select) pin sampled after reset to determine whether to enable the internal PLL (required for normal operation). Pin 38 has an alternate function as A15 for the external memory interface.