[Discuss-gnuradio] USRP1, FPGA and ADC clock

[Przemyslaw Dmochowski]

Hi,

I was wonder how the RX and TX data from/to ADC is read by Altera FPGA.

I see from the schematics that FPGA and ADC take the clock from the same

output of AD9513.

>From Ad9862 I read that the ADC data is latched using CLKOUT1, but this output is not connected

to FPGA, so at which moment is the data from ADC sampled by FPGA, with which clock?

And the same question about latching the DAC data in AD9862 send from FPGA.

I looked at the clock and it looks distorted and I wanted

to separate the ADC and FPGA clocks.

Is it possible to drive the FPGA and ADC from different clock sources? Are

different frequencies for FPGA and ADC allowed?

Do the clocks have to be synchronized? If not how much phase shift between

ADC clock and FPGA clock is allowed?

Thanks,

Przemek