AVR-Chat

> --- In AVR-Chat@yahoogroups.com, wagnerj@... wrote:
>> I think this is an inherent limit due to JTAG debugging.
>> You don't get history information out of JTAG.
> Some ICE debuggers implement an execution trace buffer (JTAG does not) but
> that is not what the OP was referring to.  If the stack frames are set up
> to support it, the debugging software can "walk" the stack to determine
> the calling context, e.g. A called B called C called D where it hit the
> breakpoint and stopped execution.  Microsoft VisualStudio does this very
> well for C/C++, showing the parameter values passed, the point at which
> each nested invocation was called, etc.
>
> Breakpoints aren't particularly useful for debugging some types of
> realtime systems, e.g. one in which you can't afford to stop the processor
> for any significant amount of time.  In these situations you have to
> instrument your code to allow it either to record important data to be
> examined at the end of a "run" or to output important data for analysis in
> real time by another computer, e.g. a PC.  Indicator LEDs and other types
> of information displays may be useful as well when the system cannot be
> stopped.
>
> Don Kinzer
> ZBasic Microcontrollers
> http://www.zbasic.net
>
>
>
>
I have handled this by implementing a "real time trace buffer". I write
certain information into the buffer (a constant indicating the function
identity, and perhaps a key variable), and maybe a key variable on exit.
It has been crucial to debugging protocol state machines for me.

Jim Wagner