How to write successfully user data to RAM in AD9957

I don't see any impact of the N-divider on the functioning of the whole system in the interpolating DAC mode, although that impact should be expected. Anyway, I have changed CFR3 to 0x123f0142 (N = 33). These settings allow generating single tone at 280 MHz (or any other) successfully, so I hope I don't need to change them. By the way, my PLL operates correctly. I have confirmed that in two ways:

1. using single tone

2. reading back the content of several registers (it proofs that my reading algorithm works ok)

However, when I try to write anything to RAM (e.g. 128 32-bit words), the read from RAM consists of 32-bit words of 0xFFFFFFFF. For technical reasons, I can't copy that data at the moment as I communicate with my DDS chip via STM32 microcontroller.

There is for sure something wrong with my RAM load procedure, which looks as follows:

short y = 0x0000;

short Q = 1;

spi_send_register(0x16); //send RAM Register address

for (int k = 0; k < 128; k++)
{

y = round(32767*cos(Q*2*3.14159*k/128));

RAMdata.bits31_16 = y;
RAMdata.bits15_0 = 0x0000;

spi_send_register(RAMdata); //send consecutive 32-bit words

}

I/O_UPDATE = 0
I/O_UPDATE = 1
I/O_UPDATE = 0

/CS = 1

I don't see any impact of the N-divider on the functioning of the whole system in the interpolating DAC mode, although that impact should be expected. Anyway, I have changed CFR3 to 0x123f0142 (N = 33). These settings allow generating single tone at 280 MHz (or any other) successfully, so I hope I don't need to change them. By the way, my PLL operates correctly. I have confirmed that in two ways:

1. using single tone

2. reading back the content of several registers (it proofs that my reading algorithm works ok)

However, when I try to write anything to RAM (e.g. 128 32-bit words), the read from RAM consists of 32-bit words of 0xFFFFFFFF. For technical reasons, I can't copy that data at the moment as I communicate with my DDS chip via STM32 microcontroller.

There is for sure something wrong with my RAM load procedure, which looks as follows:

short y = 0x0000;

short Q = 1;

spi_send_register(0x16); //send RAM Register address

for (int k = 0; k < 128; k++)
{

y = round(32767*cos(Q*2*3.14159*k/128));

RAMdata.bits31_16 = y;
RAMdata.bits15_0 = 0x0000;

spi_send_register(RAMdata); //send consecutive 32-bit words

}

I/O_UPDATE = 0
I/O_UPDATE = 1
I/O_UPDATE = 0

/CS = 1