Cortex M0+ on the Teensy 3.6?

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bc10000

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Could anyone please explain to me why the Teensy 3.6 has a M0+ ARM processor connected directly with the main M4F processor?

is this chip what the halfkey is?

I noticed it is connected to the ARM M4F chip and some how it is helping in the programming phase, but I still lack a clear understanding of what is actually happening underneath the hood.

All the best,

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Thanks for the reply Paul,

However I still need some clarification.

is the M0+ chip acting like a backup to prevent the M4F from bricking?

I dont see any USB lines going into the M0+, so I am assuming that the program file (.hex) is being written to the main chip (M4F),
and the M0+ is only helping when it is time to reset the entire system?

Is the procedure documented some where?

Thanks in advance.
 
If you are looking at making a custom product using teensy there are various threads on the topic but to answer some of the possible questions:
You will need a PJRC M0 bootloader chip with magic sauce - https://www.pjrc.com/store/ic_mkl02.html
You do not need to have anything preloaded to the main core, so that can purchased anywhere
If you want a custom loader PC side loader- https://www.pjrc.com/teensy/loader_cli.html
Once loaded you do not need a bootloader IC so it is possible to develop your product going >teensy soldered to PCB>Teensy core on custom PCB>Teensy CPU in custom PCB with a programing header mating to a re-usable bootloader IC+USB jack programer
If you want to make serial/bluetooth/ethernet updates it is possible, but the bootloader IC only supports USB so you need to add that code to your project.
 
To my mind the trick with the workings of the M0 is look where the M0 is wired into the M4; the M4 pins give you an idea of what it can do. Then consider what you do when you program the teensy, that will then give clues on how the M0 does it.

What impresses me is that the M0 does it with something like 32KB of memory only. Also when you consider the M0, you realise that the only function it can really have is to program the M4 when the button is pressed - that is almost all it can do.

But surprisingly a back door has been left on the teensy, for programming the M0.
 
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