JTAG pin sharing problem

Question

I set JTAG pins as the user I/O ,when I first programed with usb blaster ,it was ok , after that ,when I programed again it failed . WHY?

Here are the descriptions about the JTAG pin sharing :

Enables JTAG pins sharing feature in user mode. When selected, the JTAGEN pin is used to select JTAG pins (TDO, TCK, TDI, and TMS pins) operation, between JTAG operation (JTAGEN=1) and user I/O operation (JTAGEN=0). If JTAG pin sharing is not enabled the JTAGEN pin acts as a user I/O pin, and the JTAG pins (TDO, TCK, TDI, and TMS pins) are retained as dedicated JTAG pins.

The JTAGEN is always connected to 3.3v with a 10k resistor , It means JTAGEN=1.

My device is MAX10M08SCMI7G,and I use the USB blaster.

Does any one know how to deal with it??

altera_forum · Answer

I'm not sure what the problem is.  Have you tried pulling down the JTAGEN pin to GND?  It will draw power through the 10K but if this is just for development purposes that should not be an issue.

altera_forum · Answer

there is a bug on Quartus, so you need to affect TDO and use it as OUTPUT only;

from ALTERA/Support

"Why can’t I access the MAX 10 device via JTAG even though JTAGEN is pulled high in user mode?"

https://www.altera.com/support/support-resources/knowledge-base/solutions/rd03222016_95.html

"How do I gain access to the JTAG pins of my MAX 10 device if I have enabled the JTAG pin sharing option, and the Quartus Prime Programmer is unable to auto detect the device?"

https://www.altera.com/support/support-resources/knowledge-base/solutions/rd05192016_963.html

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JTAG pin sharing problem

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