I am using AD9552 with 20MHz crystal and i see it gets lock to desired frequency when i program it through SPI. Now since i have to use 40MHz crystal, i see that ad9552 is locked to the desired freq when i use 40MHz clock. datasheet says crystal spec up to 52MHz. if i use 40MHz how should i set A0-A1 pins? is it possible to use 40MHz crystal?