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TMS320F28035: tms320f28035

yoonseok shim
Intellectual 800 points
Part Number: TMS320F28035


Hi all,

I am using TMS320F28035 which uses an external crystal for SYSCLKOUT generation.

Is there any adequate SCI baud rate for an external crystal that is able to reduce clock skew between any PC and the DSP?

I guess the baud rate of the DSP can be determined and reduce the clock skew according to the performance of a Laptop in use and which program I execute on a PC for SCI communication ...      

I 've just posted this question to hear from you if you guys have any experiences with terminating skew rate ...  

thank.

  • 0
    TI__Guru 60865 points

    Hi Yoonseok,

    Are you having issues reliably communicating with the PC over SCI?  If so, what physical interface are you using? RS-232 or a virtual COM port via FTDI chip or something else?

    Generally if you are using an external crystal, the clock accuracy will be more than sufficient for the possible baud rates supported by a PC serial port.  

  • 0 in reply to Devin Cottier
    Intellectual 800 points

    The interface I am using for the serial communication is RS485. a converter from RS232 to RS485 is attached on RS232 line between DSP and PC. it communicates over SCI peripheral. 

    I am just curious about whether the baud rate exists or not that can reduce the % Error to the smallest or 0, which is described in 'Table 5. Asynchronous Baud Register Values for Common SCI Bit Rates' when the DSP runs according to the SYSCLK generated from an external crystal.

  • 0 in reply to yoonseok shim
    TI__Guru 60865 points

    Hi Yoonseok,

    Certainly it is theoretically possible to set the system XCLKIN to some multiple of the desired baud rate such that the eventual baud rate achieved is exactly the target baud rate (at least to within the tolerance of the external clock source).  However, this is unnecessary since the various serial communication protocols are generally tolerant of about 2% clock inaccuracy per party - this is well within any inaccuracy of an external XTAL and the rounding error of the baud rate selection register.  

  • 0 in reply to Devin Cottier
    Intellectual 800 points

    thanks for your tip Devin!