Altera FFT - output scaling. How to do this correctly?

First I did altera fft in 2001 !! no problem then except that the output bit resolution wasn't well done by altera, later they improved that. I did the scaling manually by bit shifting in vhdl as speed was crucial and couldn't depend on software speed. My exponent was correct at that time.

your input(x):

xreal(n) is only real, ximag is zero so the magnitude of your input is same whether you view your input as x=x(n) or x=complex (xreal,ximag).

I don't get what you say about magnitude?? but don't mix up between magnitude of a complex signal and amlpitude of a sinusoid. The maximum |magnitude| of your input(if you think of it as complex) is the amplitude of your sinusoid.

your output(y):

y is complex i.e. (y= complex(yreal, yimag)) and both elements together determine amplitude and phase(abs(y),angle(y)) in frequency domain.

Your phase info is not relevant here, phase is only relevant when comparing two sinusoids at same frequency e.g. ouput/input of a system then phase tells you what this system is doing to phase at various frequencies.