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AM6421: SPI slave count per SPI channels

Part Number: AM6421

Hi,

In one of our variant (platform based on AM64xx) we need to have up to 6 SPI slaves per MCSPI channel. Is there any hardware limitation for MCSPI to use 6 slaves per channel? I have seen 4 CS per MCSPI. Does that mean a single MCSPI can support up to  4 slave channels?

Also we need to use GPIOs as CS as many of the CS are multiplexed for some other functions. Is there any limitations to use GPIOs instead of defined CS pins?

Thank you

  • Hello Chris, 

    Thank you for the query.

    What type of SPI devices are you looking to connect using the McSPI interface?

    In general, using GPIO as chip select should not be an issue provided the interface plus the chip select logic meet the data rate requirement.

    Regards,

    Sreenivasa

  • Thanks 

    What type of SPI devices are you looking to connect using the McSPI interface?

    We need to use Threshold configurable Digital inputs using SPI interfaces . Please Refer ADE1201

    In one of our variant (platform based on AM64xx) we need to have up to 6 SPI slaves per MCSPI channel. Is there any hardware limitation for MCSPI to use 6 slaves per channel? I have seen 4 CS per MCSPI. Does that mean a single MCSPI can support up to  4 slave channels?

    Do we have any practical limitation for the number of slave device per SPI interface?

  • Hello Chris, 

    Do we have any practical limitation for the number of slave device per SPI interface?

     The SPI  device is selected based on chip select enable and not address. If you are looking a  interfacing X 6 of these devices, other than the chip select pins i do not see any other limitation. 

    I have seen 4 CS per MCSPI. Does that mean a single MCSPI can support up to  4 slave channels?

    I will have to check on the use case for providing 4 CS per MCSPI. For you applications, any of the GPIO could be used for CS.

    Regards,

    Sreenivasa

  • Thanks Srinivasava,

    I got the point that we can use GPIOs instead CS.

    My other query was related to the number of slaves that can be connected to a single MCSPI port.

    In some slave device datasheets, they may define the maximum allowed number of devices in an SPI channel for proper working. I know theoretically no number defined as such, but in practical scenario do we face any driving issues or clock capacitance issues or any such hardware limitations  if we use 6  or more slave devices under a SPI master channel?

    Thank you

  • Hello Chris, 

    Thank you for the query.

    I am not aware of any limitation on The number of slaves. The limitation comes from the system design and there could be ways to resolve including buffering or daisy chaining.

    Regards,

    Sreenivasa

  • Hello Chris, 

    I have not heard from you and closing the thread.

    Regards,

    Sreenivasa