MAX10 JTAG inaccessible after programming

Hi,

I'm working with a MAX10M04 and am having some programming issues. The programmer always reports "(failed)" in the progress bar when programming is complete and no further JTAG access is possible without power cycling. Error 209040, "can't access JTAG chain", is reported in the log. Despite this, the device appears to be configured correctly, suggesting the JTAG becomes non-functional once the design goes live. Initially I'm just using CRAM and have not attempted to program the flash.

Quartus configuration settings are:

• nCONFIG, nSTATUS and CONF_DONE disabled (these are pulled high on the target board)
• JTAG pin sharing disabled
• Unused pins: as input tri-stated

The JTAG pins are dedicated and not connected to any user logic on the PCB.

I'm fairly new to using the MAX10, so I expect there's something I've missed. Does anyone have any suggestions please?

Sparky