MC 68040 debugging via JTAG with gdb?

I don't believe the 68040 has a JTAG port. All the hardware debuggers I'm aware of for this processor are full ICEs that totally replace the CPU.

If you want to use gdb on this processor, you will need to port gdb stubs (I find it hard to believe that nobody has done this before...) and connect over serial, Ethernet or whatever other interface is readily available in your target system.

It has, but I don't know which software is needed to use it.

What is a stub?

greetings Carsten

GDB stub is a piece of code in the target system. The stub understands the GDB remote debugging protocol and functions as the GDB's resident agent reading and setting register contents, memory contents and breakpoints.

The stub functioning and structure is documented in the GDB sources and documentation.

Googling 'gdb stub' gave about 43000 hits, at least the first couple of pages fully relevant to the question.

ok

Thx, your abstract is much more clear than the hits (for me).

Interesting concept, but I don't know if I can use it. The problem is, what do I do if my programm is crashed. I think a stub is than "crashed", too.

greetings Carsten

It depends.

If the stub is run interrupt-driven and the main code crash did not succeed in destroying the interrupt environment, you may still succeed in making a post- mortem of the crash.

IMHO, the main use is in normal debugging, i.e. running until a breakpoint, looking at variables, etc.

I have written a stub for ARM7TDMI and run it successfully for a couple of years. As there are graphic front-ends for GDB, it is actually a nice debugging environment for an embedded system.

Regards from Helsinki, the home city of Linux.

The MC68040 doesn't have any in-circuit-debug support.

Thx for this clear statement.

Gruß Carsten