Looks like the 05 is not capable of floating point math.  I think I'll need that.  Looks like the 06 is it.

Foating point is not necesary for a THC. All you need really need is some way to get a scaled value in for the set point and compare it to the A2D and then make greaterthan/Less then descisions.

I wouldn't need floating point math to compare two voltages?  The voltage readings should be doubles.  Not sue how many decimal places there would be but it won't be an integer.  When I compare, am I actually comparing the numbers or an I comparing the hex equivalent of the number or the 16 bit word sitting in the analog input register?