ARM Technical Support Knowledge Articles

HOW TO RE-ENABLE JTAG ON LPC21XX DEVICES

Applies to: MCB2140 Evaluation Board

Answer


Information in this article applies to:


QUESTION

I mistakenly disabled JTAG communications on my MCB2140 board and want to re-enable it. I've tried re-programming or erasing flash using the Philips LPC2000 Flash Utility, but every time I try to connect I get the message:

Cannot communicate with test board!

My serial connections are correct. How can connect to the device to re-enable JTAG?

ANSWER

The following low-level flash erase procedure re-enables JTAG for the MCB2140 evaluation board. This procedure also disables the watchdog timer.

  1. Unplug power from the board.
  2. Make sure jumpers J7, J9 and J10 are removed and jumper J1 is installed.
  3. Make sure a standard DB9 serial cable is connected from your PC to COM0 on the board.
  4. In Windows, start the HyperTerm program.
  5. Set up the HyperTerm connection for 9600 Bits/Second, 8 Bit Data, No Parity, 1 Stop Bit, No Flow Control.
  6. Apply power to the board.
  7. On the board, press and hold the INT1 button, press and release the RST button, then release the INT1 button.
  8. In HyperTerm, type the ? character. The word Synchronized displays.
  9. Type Synchronized, then the Enter key. An OK displays.
  10. Type 12000, then the Enter key. An OK displays.
  11. Type U 23130, then the Enter key. A 0 displays.
  12. Type P 0 26, then the Enter key. A 0 displays.
  13. Type E 0 26, then the Enter key. A 0 displays.

The flash is now erased. You may now debug and download via JTAG as before.

MORE INFORMATION

SEE ALSO

Article last edited on: 2006-11-30 12:05:04

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