This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM71 interface question

Other Parts Discussed in Thread: LM71


I currently have an LM71 temperature sensor interfaced with an fpga on my pcb.  In looking at the datasheet for the LM71  I was not sure if I should have the fpga drive the SC, spi clk to the temp sensor, for 16 clocks or 32 clocks.  At present here's a brief description of what I do after a board reset has been initiated and de-asserted:

1) Write the shutdown control to the temp sensor (32 clks)

2) Write the continuous conversion command to the sensor (32 clks).

3) Drive out 16 clks on the SC expecting timing as in fig 7b. 

This seems to be working.  However, as I read in the first paragraph of the Serial Bus Interface  in Section 1.2 of the datasheet I see that "A complete transmit/receive communication will consist of 32 serial clocks."  Then, does that mean I need to provide 32 serial clocks to the sensor all the time?  Then, I see Figure 7b and I'm led to believe that once the sensor is in continuous conversion it will always send data out on every 16 clocks.



  • Hi Peter,

    Thank you for your inquiry. Should you provide 16 clocks or 32 clocks? It depends on what you want to do. Normally, reading the temperature data is only required 16 clocks, but when you want to place the device into shutdown mode or conversion mode. You must provide 32 clocks in order to write into the LM71 device. That’s what the phrase is referring to. We normally recommended customer providing the clock no more than 32 clocks. Doing so might place the device into a weird mode.

    I hope this helps. Please let me know if you have further question.