Hi,
As you can see in the ADSP-21369 datasheet the serial port can run at a maximum speed of 50Mbits per second. Depending on the CCLK speed of operation of the DSP, the maximum serial clock speed which can be achieved is one-fourth (0.25) of the processor’s internal peripheral clock (where PCLK=CCLK/2).
Kindly provide more details regarding your application so that we can assist you better with the issue.
Thanks,
Harshit