Programatically set debug mode

RE: Programatically set debug mode

ketiljo — Wed, 11 Aug 2021 12:45:39 GMT

There are a lot of digital circuitry around the MCU that ties the different parts together. NAND gates are heavily used to perform logical operations. Most of this is done by design and not really programmed. The only way to change this it to change the metal routing layers that connects the gates together, just like a good old fashioned TTL circuits on a PCB.

RE: Programatically set debug mode

Robin — Tue, 10 Aug 2021 15:26:19 GMT

Hello again Ketiljo, and thank you for your response,

So, if I am understanding you correctly, it would indicate that the HW block is hard (mask) programmed. Is this essentially correct? Just a curiosity on the core technology of the chip.

Robin @ TL

RE: Programatically set debug mode

ketiljo — Tue, 10 Aug 2021 13:14:37 GMT

The reset pin is shared with the debug interface (SWDIO) on the nRF51-series devices. There's a HW block that enables the debugger/programmer after reset has been toggled a number of times. This is described in the reference manual, chapter 11

https://infocenter.nordicsemi.com/pdf/nRF51_RM_v3.0.1.pdf

There are no registers that can override this, sorry.

RE: Programatically set debug mode

Robin — Mon, 09 Aug 2021 14:19:05 GMT

Hello Ketiljo,

Thank you for the response..

Please answer the following question relative to chip capabilities, not Nordic policy:

Would it be physically possible to disable the nRESET pin with something along the lines of a "custom soft device" implementation?

Thank you,

Robin @ TL

RE: Programatically set debug mode

ketiljo — Mon, 09 Aug 2021 12:09:33 GMT

The reset pin can't be assigned to another pin, sorry. Neither can it be disabled in normal mode.

It's generally not a good idea to se a widely used connector like USB for something else so the best here will be to either use cables with only VBUS and GND and no data lines or re-design the board to have the programming pins on a separate connector. There's always a risk that someone uses a normal USB cable here so the latter is really the safest way,.