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LMH2832: Avoid SPI write while performing an SPI read

Prodigy 60 points

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Part Number: LMH2832

Dear TI Support, Please refer to the LMH2832 specification page 22, "Programming (continued)", Figures 45. SPI Write Bus Cycle Timing Diagram and Figure 46.SPI Read Bus Cycle Timing Diagram. How can writing to an SPI register be avoided when doing an SPI read shown in Figure 46., whatever the SDI (data in) signal has for its last 8 (data) bits, whether tri-stated or not, will be written into the addressed register targeted for a read on the 16th rising edge of SCLK, there is no protocol or signal to indicate a read rather than a write is in progress? In the Figure 46.SPI Read Bus Cycle Timing Diagram, what does the arrow from SCLK 2 to 1 mean? And what does the arrow from SCLK to SDI mean? How can an LMH2832 SPI register be read without being written?

Thank You Chris Raynolds

  • Hello Chris,

    The difference in configuring to the SPI write bus cycle vs the read cycle is based off the data latched from the SDI pin during the first rising edge of SCLK. In the timing diagrams, SDI first sends a low bit in figure 45 to configure to a write bus cycle and sends a high bit in figure 46 to configure to the read bus cycle.

    Best,
    Hasan Babiker
  • In reply to Hasan Babiker31:

    Thank You Hasan for taking the time to direct me in what I should have recognized.

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