I am writing a program that is doing a bunch of things with the Apollo3 clock mechanisms. I was doing some low-level debugging that involved setting a breakpoint at the very first instruction of my code image. To my surprise, I noticed that the 32 KHz XTAL was already enabled even though its post-RESET state is to be disabled. The surprise was momentary until it occurred to me that any program I write will inherit a bunch of initialization left over from running the Sparkfun SVL bootloader. But that made me surprised again: does the Sparkfun SVL bootloader on an Artemis module require an XTAL to operate? If not, why did it get enabled?
Since the Apollo3 processor does not actually need an XTAL to operate, I had assumed that the presence of the 32 KHz XTAL in an Artemis design would be optional. But perhaps the Sparkfun bootloader turns on the XTAL so it can operate reliably at much higher transfer rates than the Ambiq bootloader. That would be fine, except for the implicit dependency that every Artemis module design will require a 32 KHz crystal.
So: does anyone know if the SVL and/or Ambiq bootloaders require the 32 KHz XTAL?