Sorted my problem the other day. So for anyone else who ever wants to know - facnrm appears to control how the math51.lib functions read a float from memory. When you have a IEEE754 constant in ROM like this...

declare fp_ROM_273_15 (4) byte constant (033h, 093h, 088h, 043h); /* 273.15 kelvin */

...then you need to set facnrm true before referencing it, like this...

facnrm = TRUE;
call fp_link(call_fpsub, .fp_ROM_273_15); /* convert to celcius */

But don't set facnrm before referencing an auxiliary.

Someone on comp.arch.embedded thinks the library came from US Software (Lantronix).

--
Rich