I'm afraid not You will be getting an exception. Take a look at the api for set_clock_src in xs1.h...Is there any reason I can't use bit 0 of a 4-bit port instead of a 1-bit port? If I change XS1_PORT_1F to XS1_PORT_4C (or 4D) in the XN file then USB enumeration fails. Our XTAG seems to have gone missing so I'm not sure exactly where it's falling over.
It does, but only initially. The second stage bootloader (the one loaded from flash) re-programs the PLL at boot time according to the xn settings before the main image is loaded and run.Ah - I was thinking that the frequency was fixed by the PLL multiplier set by the MODE[1:0] pins, and that the XN file had to reflect that.