I am attempting to write and read the internal RAM in the AD9957. It is not working. Here is my procedure:
1. Set RAM Enable = 0.
2. Drive RT pin low, then high.
3. Write to RAM Segment Register 0: RAM Address Step Rate = 1; RAM End Address = 3; RAM Start Address = 0; RAM Playback Mode = 4
4. Set RT pin low, then high.
5. Write 4 values, one a time, to address 0x16.
6. Set RT pin low, then high.
7. Read back 4 values, one a time, from address 0x16.
The four values that I read back in step 7 are all identical. They match the last value that I attempted to write in step 5.
What could cause this behavior?