AD5271 does not update the resistor value


Before create this thread I tried different SPI command sequence in order to update the resistor of the AD5271.

Currently I am doing the following:

    AD5271 connected to a FPGA.

    CPOL => '0'
    CPHA => '1'

    SCLK frequency 200kHz

System boot.

1. 0x2400 = device is removed from shutdown mode

2. 0x1C02 = allow update of wiper position through digital interface

3. 0x0400 = write zero-scale

After the step 3, dport value is updated sendidng the command (0000 01XX XXXX XX00) at 100 hz frequency (SCLK still 200Khz). 

Resistor value never changes. 

Do you have any hint about what is happening?