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Why strange pin-out and no GND on extdbg header?

Julian Day
Prodigy 20 points

Hi,

I've got my EK-LM4F120XL boards and I want to use the Green Hills Software IDE and probe. However, this board doesn't seem to have a standard JTAG header for the purpose. There is access to the TCK/TMS/TDO/TDI pins, but the order of the pins is more like EJTAG v2.5 as was used with MIPS CPUs and GND is lacking on that connector, the nearest GND pad seems to be on J2 or J3.

I don't understand why a standard connector wasn't accommodated, such as the 1mm CoreSight 10pin connector (preferably with a premounted header) on the board, so that a standard 3rd party debugger can easily be used.

Also why for that matter was a different, non-standard pinout used on the underside for the other CPU? Why not use coresight for that too? In fact, why not go the whole hog and allow both to be used in one JTAG chain when the CoreSight header is used? I think that might then mean that the board doubles as a dual CPU dev platform.

I suspect it is too late for this board, but if you're listening, please consider this for future designs.

Thanks,

Julian

  • 0
    Prodigy 20 points

    Ok, so I did a bit more digging and I can see the 'non-standard' pinout for the ICDI JTAG is actually pretty standard for the MSP430, I'd just not come across it before, being fairly new to TI. Still I'm mystified how you're supposed to use the extdbg in a clean way with no GND on the connector.

    Thanks,

    Julian