Can an MCU determine if it is running with a BDM connected?

[wrljet]

Is there any way the MCU can tell if it is running with a BM connected?

Specifically interested in MCF51AC256, but it applies to 9S08 chips as well.

Bill

[rocco]

Hi Bill,

I don't think you can tell whether or not the BDM is connected, but you can often tell if the previous reset had been from the BDM. I say "often" because about 10% of the time my GB60 system detects the BDM reset as a ~RESET-pin reset instead of a BDM reset. Hopefully, that is fixed  in later S08s and the ColdFire parts.

The reset-status-register (SRS), which would normally have one bit set which indicates the cause of the previous reset, is all zeros when the reset is from the BDM.

BTW: This also works with the HC08 family when running from the emulator (MMDS, MMEVS or FSICE). It is 100% reliable, as opposed to the S08GB60.

[wrljet]

The reason I am interested is this...  I am developing firmware to control some hardware

I'm also building at the same time.  I have the code sprinkled with HALT instructions so

I can carefully single step over sections of code and make sure it's not doing something

destructive to the hardware being controlled.

I would like to arrange things so if the MCU starts up w/o the debugger, that I can make

it just spin in a loop or something, so it doesn't run ahead and do who knows what to

my hardware gadget.

Prompted by your post, I see there's a SRS_POR bit.  If I detect that one, I could just spin in a loop.

Bill

[rocco]

Hi Bill,

Yes, that should work. However, I would also add some of the other bits as well, such as COP and LVI. You don't want a power-supply problem breaking you out of your loop.

Come to think of it, maybe any non-zero SRS should put you into that loop.

[wrljet]

I do currently have tests on some of those bits, causing a HALT, so if I run off into

the twilight zone, bad opcode, address, etc. under the debugger, I can more easily

tell that's happened.  Very handy.