Nios II dying after a few minutes running randomly
I have a design and randomly the Nios II is dying.
--- Details---
- There is a system "heartbeat" counter which is an indication the Nios has stopped - when it does stop, it stops at the same time after reset (power on reset or JTAG reprogram) at about 4 minutes +/- 100ms.
-The Nios is dead; when the fail event has happened I can no longer connect to the Nios through JTAG. A reset is needed to reconnect.
- The surrounding FPGA logic is still functioning. Some of the peripherals I can still see functioning and I can view signals through signal tap when the Nios is dead.
-It happens randomly, most "sessions" go without issue.
---- Things I know ---
- It is not power supply related as far as I can tell; it happens both from power on reset and JTAG load reset.
-The clocks and reset to the Nios look normal when its dead ( I can view them in signalTap).
Can anyone recommend other things to explore ?
Thanks !