I found the problems come from other SPI devices on board, which should be disabled but I didn't.
"Ju, Jian" ?ÈëÏû?ÐÂÎÅ: snipped-for-privacy@nsserver1.polyu.edu.hk...
Hi all,
>
> I'm trying to run the ADC chip LTC1407a on the spartan 3e starter kit.
> Both the function and timing simulation is validated and the signal
> AD_CONV and SPI_SCK is just as wanted when I use an oscilloscope to
> observed the board signal. In other words, 34 SPI_SCK after 1 clock period
> of AD_CONV. However, the data output is always 0x3FFF when a 10kHz sine
> wave is applied on both channel.
>
> Firstly I used a 50M clock and as it can't work properly, I lower the
> clock using the internal DCM to 10MHz and use the chipscope to get the
> signals out. I found the signal SPI_MISO, which is the output serial data
> from the ADC, is always '1'. But the signal on board observed by
> oscilloscope keeps changing '0'/'1'.
>
> Any suggestions?
>
> Thanks,
> JJ
>