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TMS320F28379D: Difference between SPI low-speed and high-speed mode

Thuan Duong
Intellectual 455 points

Part Number: TMS320F28379D

Dear TI officer,

May I ask you the difference between SPI high-speed and low-speed mode, as well as the SPI high-speed capable pins ? Because I did an experiment where I tried transferring a string of 64 words from one TMS320F28379D Delfino board to another, using high-speed mode with SPI high-speed pins and then low-speed mode with normal SPI pins. In both cases, I set the SPI baud rate to be at maximum speed 12.5 Mbps ( where LSPCLK = 50 MHz, SPI_BRR register value is 0). The execution time is measured for both cases, and I see there is no much difference. The high-speed mode is only a little bit faster than low-speed mode, around some 30 to 40 ns. Conclusively, it is not any faster, isn't it ? 

Regards,
An.

  • 0
    Genius 5885 points

    When setting the SPI CLK to 12.5 MHz, the only difference between normal and high speed mode is the rise time on CLK and MOSI signals.

    For using high speed mode, you will have to change LSPCLK to run at 200 MHz. This way you can have SPI CLK rate at 50 MHz in high speed mode as the rise time of CLK and MOSI signals is high enough to support this.