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TMS320F28335 - GPIO28 - SCI bootloader and External Memory Zone 6

Johan Deben
Intellectual 655 points

Other Parts Discussed in Thread: TMS320F28335

Hi,

I'm using the TMS320F28335

If want to use External Memory Zone 6 (XZSC6), this is muxed on GPIO28 with SCIRXDA, does it mean i cannot use sci bootloader anymore?

Regards

Johan

  • 0
    TI__Guru 61235 points
    Johan,
    First, do you need zone 6? Can you use zone 7 instead?

    Second, if must use zone 6, then you could design the hardware so that there is no risk of contention between SCIRXDA and XZSC6 signals. For example, XZSC6 is an output and only drives when the MCU is making an access into zone 6. Do not make an access during boot loading. Similarly, you will need to de-select whatever is talking on SCIRXDA after the bootloader, such that hopefully that device hi-Z's its TX line (connected to SCIRXDA).

    Third, another alternative is to write your own secondary bootloader using the SCI and avoid pin GPIO28. You would put this code in flash sectorA, and have it run at reset. It can check other GPIO(s) to determine if you want to bootload new code, or just run what is already in the flash. You would put your main app in the other flash sectors. Sector A is never erased during operation.

    Regards,
    David