I want to change the FTW register(Address 0x07) through SPI writing operation
to control the output frequency. I send the register data several times and can
make it but change many times, for example, 80 times, the output frequency is
not able to controlled by the sent data.
From the AD9910’s datasheet, we can see that the data source of frequency is
parallel data port and FTW register when parallel data port enabled and data
destination is frequency. Whether FTW register and parallel data both influence
the output frequency, since the parallel data is only 16 bits.
You use address 0x07 register for the FTW when RAM is enabled and data
destination is phase, amplitude, or polar.
Otherwise, use the single tone profile registers to change frequency. Make sure
to set the profile pins accordingly too.
For example, to change the output frequency use address 0x0E and set the three
profile pins to logic zero.
Sorry for any confusion in the data sheet.