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Original question:

TMS570LC4357: SCI , LIN using SCI1 and 2

TMS570LC4357: resolution of baud rate on SCIs Lin's

john young
Intellectual 490 points
Part Number: TMS570LC4357
Other Parts Discussed in Thread: HALCOGEN

seems like when I try to configure a baud rate for the SCI/LIN modules that is , say 1Meg.....the buad looses resolution...

just want to know how accurate I can get it....guesing using a really off the wall OSC freq in (like 14.73865M). might do it?....

again....just trying to get things to run as quickly as I can to develop some code/hw

per sop...thank you very very much

  • 0
    TI__Guru**** 197286 points

    Hello,

    The SCI uses the 24-bit integer prescaler P value of BRSR register to select the required baud rates. The additional 4-bit fractional divider M refines the baudrate selection.
    In asynchronous timing mode, the SCI generates a baud clock according to the following formula:

    SCICLK Freq = VCLK / ( P + 1 + M/16 )

    and   Async baud rate =  SCICLK Freq / 16

    When VCLK=75MHz, if you need baudrate=1MHz, then P+1+M/16=75/16= 4.75 -->P+M/16=3.75

    You can choose P=3, M=16*0.75=12

    The HALCoGen doesn't support M fractional divider.