AD7765 SPI Compatible?

Hey All!

We have an AD7765EDZ board which we want to connect to our FPGA. We want to use the SPI instead of SPORT, is that possible? To work without EVAL-CED1Z we changed the 0 Ohm resistor from R11 to R29 position. Can you suggest us some connection schem to make that board fully compatible with SPI?

Thanks in advance.

Ronaldo

  • 0
    •  Analog Employees 
    on Mar 30, 2012 5:30 PM

    Hi Ronaldo,

    Changing the clock source to come from the crystal oscillator takes care of the MCLK signal source.

    This MCLK is the core clock to run the ADC conversions and also times the output data rate signal FSO and the data clock SCO.

    The interface as you know is set up in Master Mode - i.e. the ADC is the master - using sport the AD7765 is fully synchronised interface giving the Frame (FSO), Clock (SCO) and data (SDO) all synchronously transferred.

    The SCO is a continuous clock which clocks data out from the ADC.

    When you say you want to use SPI on the FPGA - does this mean that you have some standard instantiated SPI block on the FPGA?

    SPI as a "standard" has many forms. The serial clock is a burst clock so you would need to frame our SCO and ensure the correct polarity with the SPI scheme being used and also ensure that the SPI port can handle 32-bit transfers - the "standard" allows only for 8 & I think 16 bits.

    Can you send any details of the SPI port you are going to use?

    Can see then what the most efficient way to implement it is.

    Do you need to write to the AD7765? i.e. are you changing the power mode or decimation modes by using the internal registers?