ARM Debug Interface

armmicroprocessor

I was reading about debuging the code for ARM Cortex-M based MCUs. Moreover, I read about ARM Debug Interface, so What is ARM Debug Interface?

Best Answer

The arm has something called macrocels, the most used are,

Information Macrocel, Trace macrocell, Embedded trace Macrocell, Bus macrocell and so on.

The main use of these is that it provides an insight of what is actually happening inside the processor. These macrocells are hardware inside the processor which collect information about the what was being processed and sends this information to the PC via the Jtag usually. And on the PC you have a software development kit whihc shows you the results that were obtained from these. Thus giving us an insight on whats happening inside therby helping us for example debug the code, view the interrupts that occured etc.,

Related Solutions

Electronic – ARM Cortex reset button and debug interface (SWD)

Discharge energy of a 100nF capacitor at 3.3V is roughly 550 nanoJoules. That's not a lot.

The debug interface will probably have strong drivers or an open collector that will cope with this. It has to be fairly robust in order to survive ambient electrostatic discharge while not plugged in. If that's a recommended circuit or one used by someone else then I'm sure it will be fine. If you're really worried put another one of those 22R in series with it; you can swap it later for 0R on the PCB if you want.

Electronic – 8-pin ARM JTAG interface header

That isn't a standard JTAG pinout. If it is JTAG, though (which isn't a given), there are ways of mapping it out. For the sake of reference, let's number the pins:

Pin 8 is almost certainly ground -- it looks like it's connected to the ground plane.

Pins 3, 4, 5, and 6 look like they have resistors pulling them to ground. If I'm correct, this means they're inputs: they're likely to be some combination of TDI, TCK, TMS, and possibly TRST.

One of the remaining pins will be VCC. You should be able to find it by checking continuity to other known power nets on the board. Another one will be TDO; there's no obvious way to identify this one.

Beyond this, your best bet will be some combination of:

Look up the pinout of the CPU and map out continuity to known JTAG pins on the chip.
Guess a pin configuration, hook up a JTAG adapter, and see if it can pick anything up.
Use a software tool like JTAGenum to automate this guessing process.

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Related Solutions

Electronic – ARM Cortex reset button and debug interface (SWD)

Electronic – 8-pin ARM JTAG interface header

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