1980 xs stator 56v all three?

[elkriverscott]

1980 400 xs special Stator AC at 56 volts for all three white wires. Supposed to be 75? Good, bad? Ohms @ .6 all three

 

[BBS360]

The 80 400 xs has a combination regulator/rectifier?

Separate regulator and regulator.

I do the rectifier test in multimeter diode mode?

Yes.

Another test for charging is the stator.
Is the coil part of the stator unit?
Is the stator also called a coil?

The stator has the three while leads coming from it. There's also a field coil. There are separate resistance tests for the three stator leads and the field coil.
There are coils of wire in the stator but you wouldn't call it a coil.

Might you know which years i can purchase parts for this bike for? 80-81?

80-82, but 82 was the first year of the DOHC XS400 which has no compatible parts, so 80-81 is usually the safer bet.