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TLC6C5712-Q1: SPI Bus Sharing Options

stomp
Genius 4625 points
Part Number: TLC6C5712-Q1

Hi,

We have a TLC6C5712 device sharing the SPI bus with other devices (port expanders, etc.)

For some reason there is no dedicated chip select line on the TLC6C5712 and therefore there is no clear methods for the device to release the SDO pin.

I'd like to know what possibilities we have to use other devices on the same SPI.  Do we need to put a gate at the SDO output of the TLC6C5712?

Thanks

Stomp!.

  • 0
    TI__Prodigy 220 points
    Hi Stomp,

    The TLC6C5712-Q1 supports multiple devices in cascaded daisy-chain mode. The serial input data is available at SDO. You can refer to Figure 106 in page 55 for the application schematic. You may connect all the other devices with the TLC6C5712 in this mode.

    Thanks and best regards,
    Felix
  • 0 in reply to Felix Wang
    Genius 4625 points
    Thanks Felix,

    I can't understand how the TLC6C5712 device releases the SDO pin. It looks like as soon as I send the first SCK data is available at the SDO pin, this means its 100% not compatible with other SPI devices, unless the TLC6C5712 device supports a chip enable and can release the SDO line.

    Maybe we need to add an external tristate buffer?

    Thanks
    Stomp!.
  • 0 in reply to stomp
    TI__Prodigy 220 points

    Hi Stomp,

    Your understanding is correct, the TLC6C5712 will not release the SDO pin, but it doesn't mean it's 100% not compatible with other SPI devices.

    It depends on whether the other devices support dasiy-chain mode. If so, you could still set them in dasiy-chain connection, for example, if there are a number, N, of daisy-chained devices, a communication cycle comprises 16*N SCK cycles with corrsponding data transferred to corresponding shift registers on the rising edge of LATCH (for different devices, this signal may called different name).

    Please let me know if you have any questions.

    Thanks and best regards,

    Felix