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TMS320F28032: SCI baud rate upper limit with 60MHz SYSCLK

Howard Zou
Genius 12365 points

Part Number: TMS320F28032

Hi,

I wonder do we have suggested baud rate upper limit for SCI module.

Since increase baud rate will increase the %error, do you know what's fasted baud rate you see the customer is using?

Or could you please provide the %error vs. baud rate?

Since Table 12-3. Asynchronous Baud Register Values for Common SCI Bit Rates in TRM only offers 5 values. Do we have more?

  • 0
    TI__Genius 17315 points

    Howard,

    As you know, the SCI baud rate is determined by the Low-Speed Peripheral Clock (LSPCLK) and the baud select registers (SCIHBAUD and SCILBAUD - 16-bit value).  The maximum baud rate can be calculated by LSPCLK/16, so for a 60 MHz F2803x device, the maximum baud rate would be 3.75Mbps.  You are correct that as the "Ideal" baud rate values increase the error increases for the "Actual" value. We do not have other values calculated except for what is in the table.

    To calculate other values, the SCI baud rate would be LSPCLK/((BRR+1)x8).  The BRR must be an integer, so it needs to be rounded to the nearest integer number.  The reverse calculation with integer BRR gives real data rate, of which the % error can be calculated.

    There is some discussion about the maximum baud rate in the following thread:

    https://e2e.ti.com/support/microcontrollers/c2000/f/171/t/850683

    I hope this helps. If this answers your question, please click the green "Verified Answer" button. Thanks.

    - Ken

  • 0 in reply to Ken Schachter
    TI__Genius 12365 points

    Ken,

    thanks.

    Now the customer is trying to achieve baud rate of 112500 between 2 F28032.

    Since they need isolation, SCI will take only 2 channel isolator, SPI will take 4 channel isolator which cost more.

    So they wonder if it's applicable to achieve 112500 baud rate between 2 F28032, what special consideration need to be taken.

  • 0 in reply to Howard Zou
    TI__Genius 17315 points

    Howard,

    It is hard to give an exact answer.  For example each device family varies in terms of the baud rate configuration error (target baud compared to actual configured baud).  That is, 115200 might work well on the F28004x, but may not be as well on the F2833x or F2803x.  Perhaps a manual correction to the calculated value might help.  Please see the end of the following thread:

    https://e2e.ti.com/support/microcontrollers/c2000/f/171/t/894344

    I hope this helps. If this answers your question, please click the green "Verified Answer" button. Thanks.

    - Ken