I am using two AD9271 chips to construct a 16 channels DAQ device. The ADC chips were controlled through FPGA. Recently I found that I can read the memory map register value from either of the chips, but the writing commands to the chips were just ignored. Any idea what might be the cause to it?
The fact that I can read the default register value from the chips shall demonstrate that the SPI configuration channels are working properly. However, when i try to write to the register, by sending the sequence shown in the first diagram of the attached ppt file. It should trigger output test mode to send one bit high test data but nothing happens.
After writing to the register, I then read from the same register but it still stays at the default value. As can be seen from the 2nd and the 3rd diagram of the file.
The datasheet does mention that when connecting multiple chips, the Voh shall be sufficiently high. So I have also tried configuring one of the two chips at a time but it still does not work like what i expect.
Please could anyone has experience on this give me some advices?