FAQ: JTAG chain detection does not work with Atmel AVR

Filed under FAQ / Atmel JTAG

Q: JTAG chain detection does not work with Atmel AVR


On some ATmega devices (i.e. Mega128L) IDCODE masks the data from TDI input The JTAG instruction IDCODE is not working correctly. Data to succeeding devices are replaced by all-ones during Update-DR.

If the Device IDs of all devices in the boundary scan chain are to be captured simultaneously, the ATmega128 must be the fist device in the chain.
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