The fading effect implement in 863x

There are many ways to implement this, but the present here only use one scaler. The idea is to display picture A, and blend picture B to back buffer many times until only picture B is visible. This can be expressed in pseudo-code like this:

load_image(A)
flip_buff(X, Y)
MoveAndScaleRectangles(A->Y)
flip_buff(Y, X)
MoveAndScaleRectangles(A->X)

load_image(B)
SetupChannel(ID_Z, B);

EnableAlphaFading(ID_Z);

while(A_is_visible)
{
flip_buff(X, Y);
SetupChannel(ID_X, X);
SetupChannel(ID_NX, Y);
SetupChannel(ID_Z, B);
AlphaPalette(1 to 255);
BlendAndScaleRectangles( B->Y);
}