Hello! I am having an issue at the moment. I use freeRTOS with the AT91SAM7S and it works perfectly fine for my application. Problem is, I recently found that I need to use the SYS interrupt to the DBGU. The PIT, the system tick, is connected to the same interrupt! I located the interrupt handling function in port.c, BUT… Is it safe to implement DBGU-mask inside that fucntion to run parallell to the system tick interrupt??!! Any particular precautions recommended?? Thanks!! //MB 

I am not familiar with the working of the DBGU, but can offer some suggestions. If you can use the same frequency at the RTOS tick (or some subdivision of), and access to the DBGU will not cause any blocking (polling etc.) then you might be able to use a tick hook  a call to a function that you define to perform the DBGU handling you require.  This can be added to the very end of vTaskIncrementTick() within tasks.c so it gets called each tick.  Normally it would be good to keep this in the port.c file, rather than in the kernel code, but the IAR compiler requires the tick to use an asm wrapper which makes this less user friendly.  You could alternatively add a call to your function within portasm.s79. Alternatively, you could create the RTOS tick from a different source.  Does your application leave any timers free that can generate a periodic event (compare match for example?).  The timer used by the RTOS tick is set from prvSetupTimerInterrupt() in port.c.  You can use any available source. Regards.