I'm trying to find the JTAG header for an Intel X Scale (ArmV5) PXA270 board. I found and populated a 20-pin header:

ARM JTAG 20-pin header

but JTAGulator doesn't think it has a valid combination of TDI/TDO/TMS/TCK on either a IDCode or bypass scan. I put a logic analyzer on it and don't really see a steady clock:

logic analyzer 20-pin jtag

Is it possible the clock is elsewhere and some of the header pins are still TDI/TDO etc., or do any of the logic analyzer data seem they could be from JTAG?

  • Are there other headers/pads? Jun 17, 2020 at 1:35
  • Maybe its domek kind of serial communication interface (UART).
    – malikcjm
    Jun 17, 2020 at 9:29
  • does it have >5 GND pins in a row? if not, it might be not JTAG but flash or similar
    – Igor Skochinsky
    Jun 17, 2020 at 13:53
  • The JTAGulator has a UART option I can check, but does this look like UART data or something else? It doesn't have the whole row of GND (or 9 pins anyway), which is what I was expecting. I should still see a steady clock, right?
    – batflaps
    Jun 17, 2020 at 18:19


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