Real-time tracing with JTAG

[the_penetrator]

Hallo fellow members...

i have question on JTAG usage.

i recall that JTAG used to add wait states in order to perform the scan. While one of their docs stated that this was inevitable, i remember running code on ARM from SSRAM (external static RAM). (this was done because we ought to disable the cache/scratchpad RAM to perform some current measurements).

Are the above true, or in case i was running code from the cache i would get no additional wait states.

So how do i monitor real-time transactions (with expected cycle accuracy) with JTAG. Then, i would have to the monitoring in harder way...

PS: JTAG can hold nWAIT HIGH so wait states are inserted.

thank you!

the_penetrator©

 

[hugo_nz]

I am not sure if that would be possible with JTAG alone. Most ARMs have a Embedded Trace Macrocell, allowing you to do realtime traces, but it needs both a trace unit (like RealViewTrace), and a trace port on the board.

Let me know how you get on...