Hello ,
we have a serious problem with the AT91SAM7S256.

We have realized a project with AT91SAM7S256 and FreeRTOS 4.05.
We use 3 tasks with the same priority an idle task and a tick rate of 1 ms (PREEMPTION = YES).
We use the watchdog. It works.If we place a while(1); command for testing in the Main task the system restarts without any problems.
It works fine.

On some boards the systems stops after a short while.
All outputs are redefined as inputs and the xtal - oszilator stops working.
The time between startup and the problem varies from board to board (some minutes up to some days).

We are not able to debug the problem with JTAG / Jlink.
A connected Jlink changes the timing and the problem doesn`t occured.
In the past we noticed that the problem happend when we transfered and received data on UART 0 with DMA. After we have disabeled the DMA transmission it seemed to be fixed .
In the current project we use DMA only for receiving data.
We also use SPI (without DMA and Interrrupt) and TWI/I2C with Interrupt.

Does anybody has an idea or a posible reason for this strange behaviour?
Does anybody has an idea why the conroller doesn`t restart in this error case?

Thanks a lot

Rudi

Have you try to put some trace in the interrupt that is firered when the instruction is not valid ? like spurious, abort, etc.. ?

Jonathan

Have a look at the latest datasheet. There is an issue on the watchdog timer on AT91SAM7S256. It may explain your problem.