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Visitor
Visitor
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Registered: ‎01-03-2019

Re: AXI Quad SPI FIFOs with Multiple Discrete 8-bit Transfers

To reframe the question. In the section titled: "SPI Master and Slave Devices where Registers/FIFOs are Filled Before the SPI Transfer Begins and Multiple Discrete 8-bit Transfers are Performed (Optional Mode)"

Does "Discrete 8-bit transfers" mean that chip select will toggle every 8 bits?

Like in a spidev example, you'd be able to maybe setup your struct to have a time delay on each toggle using the delay_us parameter. ex)

 

    /* Transmitted Control Message */
    struct spi_ioc_transfer spidev_message = {
        .tx_buf = (unsigned long)tx_buffer,
        .rx_buf = (unsigned long)rx_buffer,
        .len = 3,
        .delay_usecs = 7,
        .bits_per_word = 8,
    };

 

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Scholar
Scholar
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Registered: ‎02-01-2013

 

I can't speak to the code snippet, but the documentation section you reference describes a scenario where a single 8-bit transfer is performed in a single transaction. A transaction is defined as what happens (inclusively) between a SPI chip select asserting, and that chip select de-asserting.

-Joe G.

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