CLKDIV_SHIFT
reg |= (2 << CLKDIV_SHIFT);
reg |= (div << CLKDIV_SHIFT);
div = (reg & CLKDIV_MASK) >> CLKDIV_SHIFT;
div = (reg & CLKDIV_MASK) >> CLKDIV_SHIFT;
reg |= (div << CLKDIV_SHIFT);
div = (reg & CLKDIV_MASK) >> CLKDIV_SHIFT;