Description
Signal integrity problems on configuration signals at power-up may make a device to enter into an unexpected mode.
Unknown devices (for example, UNKNOWN_xxxx (xxxx is a number), UNKNOWN_NO_JTAG_ID) may be detected on the JTAG chain when Auto Detect is conducted by Programmer.
Resolution
Check and improve signal integrity of configuration signals(NCONFIG, NSTATUS) to help fix the problem.