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TCAN4550: whether TCAN4550 could support 8/16 bit SPI

Zhihao Su
Prodigy 490 points
Part Number: TCAN4550


Tool/software:

Hi Team,

My customer use TCAN4550 + RK3568 for SPI transfer to CAN. But RK3568 only support 8/16 bit SPI, and i noticed that out TCAN4550 request 32 bit, does TCAN4550 could support 8/16 bit SPI? If Yes, do you have any instruction for this kind of application? Customer told me according to their testing, the driver must write as SPI->bits_per_word=32 to read whole information.

  • 0
    TI__Mastermind 34500 points

    Hello Zhihao,

    The TCAN4550 registers and Memory RAM (MRAM) communication is all based on 32-bit words and the formatting is shown in the datasheet.  Many MCU's don't support 32-bit words and it is ok for the MCU to write the bits in 8 or 16 bit increments as long as the Chip Select signal remains low for the entire SPI read/write transaction.

    If the chip select pulls High between each 8/16 bit increments, then this will result in a SPI error.  So as long as the chip select remains low for 64-bits (or the two 32-bit words) needed for a single-register read/write transaction, then the MCU can write the bits in increments of 8 or 16.

    Some MCU's have SPI driver functions that want to automatically pull the chip select line high after every 8 or 16 bits and some modifications to the SPI driver may be required to control the chip select signal so that it matches the TCAN4550 requirements.

    Regards,

    Jonathan