Advantage of using AD9637 in downgrade mode

Hello,

What is the benefit/usage of AD9637 in downgrade mode by setting register values (0x100) in register map?

"Resolution/Sample Rate Override (Register 0x100)

This register is designed to allow the user to downgrade the device. Any attempt to upgrade the default speed grade results in a chip power-down. Settings in this register are not initialized until Bit 0 of the transfer register (Register 0xFF) is written high."@

Secondly,

What is the difference between

- just using the AD9637 with a 17MHz input clock

and

- using a AD9637, downgraded to 20Msps, with a 17MHz input clock

?

Best Regards

SIqbal