can FPB be used for breakpoints on teensy4?

[edsut]

Hi,
I am trying to use the FPB unit on teensy4.1, and I *thought* I had it working but when an
address that is loaded into FP_COMPN is hit the board locks up. Then I read that FPB
apparently (note I am not an ARM expert by any means) looks like a BKPT to the ARM.
For teensy4, bkpt 251 is used to enter HalfKay, so does that mean that any BKPT
(to include FPB-invoked) will cause the running firmware to transition to HalfKay?

Fundamental question: can the FPB be used for breakpoints on teensy4?

Tx
Ed

Sorry if there's answers out there on this.
I did a quick search for BKPT, FPB and Teensy4 but didn't find any relevant posts.

UPDATE:
After posting this question it occurred to me that I can run the following test...
Establish the breakpoint using FPB, then run the code that will cause the address
to be hit (causing the lockup). Then attempt to run teensy_loader. If that is
successful (which it was), that means that FPB/BKPT can't be used with Teensy4
for debugging. If this is true, is there any other way to insert a breakpoint?

 

[edsut]

Hmmm... digging into this more, it appears that BKPT will never cause an exception; rather
it triggers a "pattern" on the debug signals (which, I'm guessing, is what halfKay catches).
So, am I correct to assume that FPB and BKPT are typically only used with an external debugger?