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DAC8742H: SPI CLOCK SELECT BASED ON FRAME RATE.

Part Number: DAC8742H

hi Every one I am new in Hart Protocol 

1.IN above Data Sheet Says the  Frame Rate greater than 2242 Nano Seconds , here i got Confused how to select Spi Bus Clock Based on Frame rate . Weather I required 1Mbits , 4 Mbits  Etc

please let me if any relation Between Frame Rate and Bits per Second. how to Drive the Bits per Second by Using Frame Rate per Second and Frame Gap Time.

2. And There Is  frame Gap Error , Were I need To Set Frame Gap Time And How to check The Frame Time Clock Count .

Regards

Manukumar

  • Hello Manukumar,

    1. SPI frame-rate/ duration refers to the time period between successive SPI frames or CS edges. This time duration needs to be greater than 2442 ns for HART mode. The gap between frames is what I refer to as CS high time. For SPI communication with CRC disbled,

    (24/ SCLK frequency) + CS (high time) > 2442 ns

    2. The gap error referenced in a datasheet refers to an error that is reported when the period between successive HART frames is longer than 1 character. This is different from the 'frame gap time' or 'CS high time'. Gap error is defined in the data link layer spec for HART communication. To avoid HART gap errors, the HART master must ensure that the duration between HART characters is always less than 1 character length.

    Regards,

    Reza

  • Hello Manukumar,

    I wanted to follow up on your question to see if you now understand how to determine the SCLK frequency. Thanks

    Regards,

    Reza