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ADS7865: CS and CONVST Inputs

James Thrasher
Prodigy 30 points
Part Number: ADS7865

Tool/software:

The datasheet indicates "Chip select. When low, the parallel interface of the device is active; when high, input signals are ignored and output signals are 3-state"

Does this statement include the CONVST input? If I have a falling edge on CONVST and CS is high, does the ADS7865 ignore the CONVST input?

Figure 32 seems to show CONVST falling edge starting a conversion when CS is high.

  • 0
    TI__Intellectual 920 points

    Hello James, 

    Thanks for the question.

    The description for Chip Select (CS) is correct, but it refers to device & host communication.  The CONVST pin is used to control the internal processes of the ADC related to the analog inputs. CONVST, and the subsequent rising edge of the clock (explained in Figure 2), initiate the conversion cycle, and along with BUSY the conversion and acquisition time are defined.

    Although the device can be read from or written to during this conversion cycle (please see Figure 1 and Timing requirements for more information on this), it is not needed to communicate with the device. A conversion can be started without reading/writing to the device or the device can be read from or written to without starting a conversion cycle.

    So CONVST does not fall into the ignored pins on the CS description in the Terminal Functions table.

     

    Best regards,

    Yolanda

  • 0 in reply to Yolanda Gonzalez
    Prodigy 30 points

    In summary, the CONVST pin is not ignored when CS is high. Thanks.