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Which pin of LM4F230H5QR is the default UART bootload enable pin?

Tang Rolan
Intellectual 425 points


I'm trying to design a new board with LM4F230H5QR, the datasheet tell me to select the enable pin according to the value of register BOOTCFG, the reset value is 0xfffffffe,

which means the pin is   the pin PH7, but LM4F230H5QR has not the pin.

  • 0
    Guru 117855 points

    Only "unique bit" I see w/in "0xfe" byte is bit 0 - suggesting that your pin is PH0.  

    Further - isn't Uart_0 the "usual suspect" for Uart Bootloader?  And - if that is so - is Port_H the most likely "residence" for Uart_0?   (although pin_mux may allow Uart_0 @ Port_H)  One would better expect that Port_A is normal/customary residence of Uart_0.

    Truth in advertising - have not looked @ spec for that M4F - but cannot justify your logic for PH7 choice.

  • 0 in reply to cb1_mobile
    Intellectual 425 points

    Sorry,I don't think your answer can help me solve this problem,think you!

  • 0
    TI__Guru 64540 points

    The LM4F230H5AQR datasheet indicates that UART0 is only available on 1 set of pins (PA0 - RX; PA1 - TX).  The ROM section, Section 8.2.2, indicates that UART0 would be used for bootloading.

    Your interpretation of BOOTCFG is partially correct, regarding the port and pin selection, BUT there is another bit that you have missed called EN (bit 8).  If this bit is cleared (ie. 0) then the PORT and PIN bit fields are used.  However, if BOOTCFG=0xFFFFFFFE, then bit 8=1 which means the PORT and PIN bit fields are not used.  Please look at the description of the EN bit in the BOOTCFG register description.

  • 0 in reply to BrandonAzbell
    Intellectual 425 points

    Dear BrandonAzbell, can I do as follows:

    1. Wnen the chip's flash ram is empty, I can download my program to the chip.

    2. Power on reset,   my program will modifies the BOOTCFG, including clearing the EN bit  and changing PORT and PIN bit fields to the values which indicate the enable pin I want.

    3. Power on reset again, if the enable pin  matches the value of BOOTCFG,    I can download any my  programs to the flash ram using the ROM bootloader