Switch reference clock input of AD9549


I am trying to switch the reference clock input from REF_B to REF_A, but the chip continues locking with the REFA Clock.

The registers have been set with these values below.

Reg : Value

0100 : 30 -- enable single tone, close loop off

01C0 : 04 --automatic control on

01C1 : 00 --disable auto switch-over, select REF A

0100 : 11 --disable single tone and close loop on

The REFSELECT (Pin 56) is not used.

Is there any other register to be configured?

Kind regards,