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TMS320F28035: SCI Tx Empty flag going high at beginning of stop bit contrary to documentation

BadMonkey
Expert 2090 points
Part Number: TMS320F28035


I am spinning on the SCI Tx Empty flag waiting for the last byte of a message to finish to disable the RS-485 driver. SPRUGH1C, pg. 18, Figure 9, shows that Tx Empty will go high when the stop bit is finished. I am finding that the Tx Empty flag is going high when the last bit of the byte's data is shifted out. This is too bad because it means that I cannot use it to control the RS-485 driver.

Can anyone confirm if SPRUGH1C is correct and that I possible have something configured incorrectly? That would be the best scenario for me.

See attached waveform drawings.

Regards,

JC

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  • 0
    TI__Mastermind 42195 points

    Jim,

    I have not tried this personally, but there are no configuration bits to control when TX EMPTY goes high. If this is the behavior you are seeing, I would not be surprised. The device most likely sees that the buffer is empty, and does not wait 1 stop bit time before setting the flag.

    Regards,

    Cody