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ADC124S021: timing and SPI reference code

Amelie Zheng
Genius 10865 points

Part Number: ADC124S021

Hi Team.

It seems quite different between these two timing but both of them come from datasheet.

May I ask the following question?

Which timing should customer follow?

What are Z3-Z0 in picture2?

Could you please help to provide the reference code about how to read the ADC data?

  • 0
    TI__Mastermind 25040 points

    Hello,

    The timing diagram above are the same, except that the last two signals are switched. 

    Note that the first image it is SDI above SDO, and in the second image, it is SDO above SDI. [DOUT=SDO, and DIN=SDI)

    On SDO, In the second image, Z3 through Z0 are the leading four zeros. In the first image, they are simply shown as low or a zero. 

    Conversion data is based on the reference voltage used, in this device that is Va. note that the device output data in binary, but the equations is based on decimal code equivalent.

    ADC output code (dec) = input voltage (V) / LSB (V)

    LSB (V) = Va / 2^12 = Va / 4096

    Regards

    Cynthia

  • 0 in reply to Cynthia
    TI__Genius 10865 points

    Hi Cynthia,

    Are SDO and SDA triggered at the same time?

  • 0 in reply to Amelie Zheng
    TI__Mastermind 25040 points

    I understand the confusion now, below is a snippet of the datasheet that explains SDI and SDO. 

    SDI changes state on the falling edge of sclk . the device reads SDI on the rising edge, which means it will be easiest for SDI to change state on the falling edge of SCLK as well.