nstatus get low periodic

You don't say what device you're using - Cyclone IV? Assuming so...

1) VCCINT & VCCD_PLL are a little low - but shouldn't stop it working.

2) Is nCE tied low?

3) Is nCONFIG driven or pulled high?

4) Does EVERY power pin have power?

nSTATUS will only go low if nCONFIG is driven low. Is that what you're doing? Is that intentional?

If points 2-4 above are true JTAG should be able to detect it.

Cheers,

Alex

It seems like your config is failing and Auto-restart is configured. From the Cyclone IV Handbook:

"Configuration Error

If an error occurs during configuration, Cyclone IV devices assert the nSTATUS signal low, indicating a data frame error and the CONF_DONE signal stays low. If the Auto-restart configuration after error option (available in the Quartus II software in the General tab of the Device and Pin Options dialog box) is turned on, the Cyclone IV device releases nSTATUS after a reset time-out period (a maximum of 230 s), and retries configuration. If this option is turned off, the system must monitor nSTATUS for errors and then pulse nCONFIG low for at least 500 ns to restart configuration."

John D

Which configuration scheme are you using? Check the configuration mode setting the Qaurtus II under the Device and Pin option settings.

Make sure the nCONFIG need to the be high all the time before the nSTATUS goes high. If the nCONFIG goes low with during the configuration which will cause the nSTATUS to go low too. In this case you need to check the POR (power on reset) monitored power supply when the moment nCONFIG or nSTATUS goes low.