Teensy 3.6 FPU and 'fuses'

[Bipman]

Hi

I was looking through the M4 technical manual and it stated that the FPU has an instruction to turn it on. Is this turned on by default? Also, on the Arduino Due, the processor has 'fuses' which can be set so that code cannot be overwritten or read back once programmed; does this exist on the M4? It wasn't shown in the manual.

Bipman

 

[UhClem]

The FPU must be enabled via the SCB_CPACR register before attempting to use it.

I haven't looked into flash protection but chapter 9 (Security) of the K66 family reference manual would appear to cover it. (with more details in chapter 32 on flash memory)

 

[PaulStoffregen]

.. the FPU has an instruction to turn it on. Is this turned on by default?

Yes, the FPU is turned on by default in the startup code.

Also, on the Arduino Due, the processor has 'fuses' which can be set so that code cannot be overwritten or read back once programmed; does this exist on the M4? It wasn't shown in the manual.

Yes, the Freescale chip has a similar feature. It's documented deep within the flash controller chapter of the reference manual.

By default these bits are set in such a way that you can't easily lock the chip in a permanent way.

 

[Bipman]

That's great, thanks for the answers.