Just a quick read of the datasheet shows the maximum internal oscillator is 16MHz.

Also, the chip has an onboard voltage regulator for 3.3VDC so I'm certain you'd have to supply somewhat more than that to actually get that voltage to the chip. Although it does say it will operate at 1.8 volts.

Not sure it matters but on the write to the value.lowbyte, you needs a space according to the book.

And now someone will add that I'm wrong so I'm not sure I'm correct.