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TMS320F28075: TMS320F28075 SCI bootloader mode

Sammi Shang
Expert 4450 points
Part Number: TMS320F28075


Dear team,

Customer found GPIO84 have conflict between Device BOOT MODE and SCI-BOOT mode.

From table 6-10, GPIO84 need to be pullup to work as SCI mode; from table 6-11, GPIO84 was used as data transmit SCITXDATA of SCI-BOOT. This make customer confuse how to set this PIN and how to use SCI bootloader mode? Hope you could give suggestion.

Thanks.

Best regards,

Sammi

  • 0
    TI__Expert 7985 points

    Hi Sammi, 

    Let us calibrate on this version of the TRM:  http://www.ti.com/lit/ug/spruhm9f/spruhm9f.pdf   because it is unclear from your reference to table 6-10 and table 6-11. 

    In the TRM at the link above, see Table 4-4, on page 560.  GPIO84 is sampled during power on reset and it needs to be pulled up high (with GPIO72 low). 

    The SCI boot mode operations will begin several cycles after the initial power on sampling of the boot mode pins. 

    Now take a look at Table 4-22, SCI Boot Options, on page 584. 

    Please let us know if that clarifies the usage of GPIO84. 

    Cheers!

    Krishna 

  • 0 in reply to Krishna Allam
    TI__Expert 4450 points

    Hi Krishna,

    Thanks for your response. So can I regard this PIN as Time division multiple Access? When power initial, it need to be pullup as SCI mode. Then several cycles later, this pin works as a data transmitter port when in SCI Boot mode?

    This question is asked for 100pin tms320f28075, I am not sure if this will affect.

    Thanks.

    Best regards,

    Sammi

  • 0 in reply to Sammi Shang
    TI__Expert 7985 points

    Sammi,

    We should not apply the term Time Division Multiplexing in this case.  Here, the pin just has a dual function.  On start up the pin is sampled to determine the boot mode.  Once the boot mode is known and latched, it is not needed to for determining the boot mode anymore and can be used for other functions, in this case TX for the SCI.

    I will mark this issue resolved and close it.  Please re-open if you have further questions.

    Cheers!

    Krishna