JTAG debugger recommendations?

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Does anyone have any recommendations for a good JTAG debugger for
Linux applications and modules?  We are running Linux 2.4 with a
Freescale MPC8248 processor.

Thank you.


Re: JTAG debugger recommendations?

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Why not use GDB?

Re: JTAG debugger recommendations?
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GDB affects the timing to the point that our system does not run.


Re: JTAG debugger recommendations?
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AFAIK, GDB _uses_ the JTAG debug hardware if configured accordingly. Am
I wrong ?

-Michael

Re: JTAG debugger recommendations?
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Try the Abatron BDI2000.  Thats what I am using, and gives source
level debugging (with MMU support) using a GDB server.  It is straight
forward to setup and works well.


Re: JTAG debugger recommendations?
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We tried the Abatron BDI2000 and it adversely affected our system.  We
have a modem running 10 ms frames, which is very sensitive if the
timing is changed.


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How can that be ? The BDM/JTAG  interface is supposed to do nothing as
long long as you don't stop the execution. Is this not true ?

-Michael

Re: JTAG debugger recommendations?
On Aug 28, 12:26 am, Michael Schnell
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All I can do is speak from experience.


Re: JTAG debugger recommendations?

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10 ms is an eternity on most modern processors. A real JTAG emulator should
have zero affect on the execution of your code. In fact a debugger shouldn't
affect timing while your code is running. I think you have something else
going on.

 Are you using a different build script/makefile when you are
debugging/emulating? A lot of times the compiler needs different options to
retain the symbol information that the emulator uses. Maybe you're
inadvertently changing the optimization level of your compiler and ending up
with slower code as a result. If it is a c compiler, for example, there is
usually a -Ox command line option to set the optimization level.

-Clark



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I don't know what the 10ms Bill referred to, but a JTAG device could
take this much time depending on the interfaces used to communicate
with the JTAG itself.  For example if your JTAG device is USB / Serial
or Network, the time taken for the debugger to communicate with the
JTAG may be more than 10ms.  Hence you get the impression that the
actual code execution takes that time.  From my understanding it
depends on the following factors.
- JTAG debugger -server side (eg: GDB server)
- Debugger - client side (GDB)
- Connection to JTAG (eg: serial port)
- How the debugger communicates (given that usually JTAGs have limited
number of HW breakpoints [eg: 2]).  Does it set a breakpoint on each
source line or is it smart enough to set breakpoints in optimised
code .... etc.etc.

JTAG itself should not have any effect on the timing (baring track
lengths, which is in pS or uS timing  and internal CPU HW delays), but
how you communicate with the JTAG pod will have a lot of bearing.
Cheers
  J


Re: JTAG debugger recommendations?
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Isn't any JTAG debugger is going to affect timing since it has
to stop the processor to do any "debugging"?  I remember some
ARM vendors bragging about how they had non-intrusive tracing
via JTAG, but I'm very skeptical.

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